parisc: Add alternative coding infrastructure

This patch adds the necessary code to patch a running kernel at runtime
to improve performance.

The current implementation offers a few optimizations variants:

- When running a SMP kernel on a single UP processor, unwanted assembler
  statements like locking functions are overwritten with NOPs. When
  multiple instructions shall be skipped, one branch instruction is used
  instead of multiple nop instructions.

- In the UP case, some pdtlb and pitlb instructions are patched to
  become pdtlb,l and pitlb,l which only flushes the CPU-local tlb
  entries instead of broadcasting the flush to other CPUs in the system
  and thus may improve performance.

- fic and fdc instructions are skipped if no I- or D-caches are
  installed.  This should speed up qemu emulation and cacheless systems.

- If no cache coherence is needed for IO operations, the relevant fdc
  and sync instructions in the sba and ccio drivers are replaced by
  nops.

- On systems which share I- and D-TLBs and thus don't have a seperate
  instruction TLB, the pitlb instruction is replaced by a nop.

Live-patching is done early in the boot process, just after having run
the system inventory. No drivers are running and thus no external
interrupts should arrive. So the hope is that no TLB exceptions will
occur during the patching. If this turns out to be wrong we will
probably need to do the patching in real-mode.

Signed-off-by: Helge Deller <deller@gmx.de>

14 files changed, 233 insertions, 62 deletions

diff --git a/arch/parisc/include/asm/alternative.h b/arch/parisc/include/asm/alternative.h
new file mode 100644
index 000000000000..bf485a94d0b4
--- /dev/null
+++ b/arch/parisc/include/asm/alternative.h
@@ -0,0 +1,47 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __ASM_PARISC_ALTERNATIVE_H
+#define __ASM_PARISC_ALTERNATIVE_H
+
+#define ALT_COND_NO_SMP         0x01    /* when running UP instead of SMP */
+#define ALT_COND_NO_DCACHE      0x02    /* if system has no d-cache  */
+#define ALT_COND_NO_ICACHE      0x04    /* if system has no i-cache  */
+#define ALT_COND_NO_SPLIT_TLB   0x08    /* if split_tlb == 0  */
+#define ALT_COND_NO_IOC_FDC     0x10    /* if I/O cache does not need flushes */
+
+#define INSN_PxTLB      0x02            /* modify pdtlb, pitlb */
+#define INSN_NOP        0x08000240      /* nop */
+
+#ifndef __ASSEMBLY__
+
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/stddef.h>
+#include <linux/stringify.h>
+
+struct alt_instr {
+        s32 orig_offset;        /* offset to original instructions */
+        u32 len;                /* end of original instructions */
+        u32 cond;               /* see ALT_COND_XXX */
+        u32 replacement;        /* replacement instruction or code */
+};
+
+void set_kernel_text_rw(int enable_read_write);
+
+/* Alternative SMP implementation. */
+#define ALTERNATIVE(cond, replacement)          "!0:"   \
+        ".section .altinstructions, \"aw\"      !"      \
+        ".word (0b-4-.), 1, " __stringify(cond) ","     \
+                __stringify(replacement) "      !"      \
+        ".previous"
+
+#else
+
+#define ALTERNATIVE(from, to, cond, replacement)\
+        .section .altinstructions, "aw" !       \
+        .word (from - .), (to - from)/4 !       \
+        .word cond, replacement         !       \
+        .previous
+
+#endif  /*  __ASSEMBLY__  */
+
+#endif /* __ASM_PARISC_ALTERNATIVE_H */
diff --git a/arch/parisc/include/asm/cache.h b/arch/parisc/include/asm/cache.h
index 150b7f30ea90..006fb939cac8 100644
--- a/arch/parisc/include/asm/cache.h
+++ b/arch/parisc/include/asm/cache.h
@@ -6,6 +6,7 @@
 #ifndef __ARCH_PARISC_CACHE_H
 #define __ARCH_PARISC_CACHE_H
 
+#include <asm/alternative.h>
 
 /*
  * PA 2.0 processors have 64 and 128-byte L2 cachelines; PA 1.1 processors
@@ -41,9 +42,24 @@ extern int icache_stride;
 extern struct pdc_cache_info cache_info;
 void parisc_setup_cache_timing(void);
 
-#define pdtlb(addr)         asm volatile("pdtlb 0(%%sr1,%0)" : : "r" (addr));
-#define pitlb(addr)         asm volatile("pitlb 0(%%sr1,%0)" : : "r" (addr));
-#define pdtlb_kernel(addr)  asm volatile("pdtlb 0(%0)" : : "r" (addr));
+#define pdtlb(addr)     asm volatile("pdtlb 0(%%sr1,%0)" \
+                        ALTERNATIVE(ALT_COND_NO_SMP, INSN_PxTLB) \
+                        : : "r" (addr))
+#define pitlb(addr)     asm volatile("pitlb 0(%%sr1,%0)" \
+                        ALTERNATIVE(ALT_COND_NO_SMP, INSN_PxTLB) \
+                        ALTERNATIVE(ALT_COND_NO_SPLIT_TLB, INSN_NOP) \
+                        : : "r" (addr))
+#define pdtlb_kernel(addr)  asm volatile("pdtlb 0(%0)"   \
+                        ALTERNATIVE(ALT_COND_NO_SMP, INSN_PxTLB) \
+                        : : "r" (addr))
+
+#define asm_io_fdc(addr) asm volatile("fdc %%r0(%0)" \
+                        ALTERNATIVE(ALT_COND_NO_DCACHE, INSN_NOP) \
+                        ALTERNATIVE(ALT_COND_NO_IOC_FDC, INSN_NOP) \
+                        : : "r" (addr))
+#define asm_io_sync()   asm volatile("sync" \
+                        ALTERNATIVE(ALT_COND_NO_DCACHE, INSN_NOP) \
+                        ALTERNATIVE(ALT_COND_NO_IOC_FDC, INSN_NOP) :: )
 
 #endif /* ! __ASSEMBLY__ */
 
diff --git a/arch/parisc/include/asm/pgtable.h b/arch/parisc/include/asm/pgtable.h
index b86c31291f0a..94c0ef7a9e03 100644
--- a/arch/parisc/include/asm/pgtable.h
+++ b/arch/parisc/include/asm/pgtable.h
@@ -43,8 +43,7 @@ static inline void purge_tlb_entries(struct mm_struct *mm, unsigned long addr)
 {
         mtsp(mm->context, 1);
         pdtlb(addr);
-        if (unlikely(split_tlb))
-                pitlb(addr);
+        pitlb(addr);
 }
 
 /* Certain architectures need to do special things when PTEs
diff --git a/arch/parisc/include/asm/sections.h b/arch/parisc/include/asm/sections.h
index 5a40b51df80c..bb52aea0cb21 100644
--- a/arch/parisc/include/asm/sections.h
+++ b/arch/parisc/include/asm/sections.h
@@ -5,6 +5,8 @@
 /* nothing to see, move along */
 #include <asm-generic/sections.h>
 
+extern char __alt_instructions[], __alt_instructions_end[];
+
 #ifdef CONFIG_64BIT
 
 #define HAVE_DEREFERENCE_FUNCTION_DESCRIPTOR 1
diff --git a/arch/parisc/include/asm/tlbflush.h b/arch/parisc/include/asm/tlbflush.h
index 14668bd52d60..6804374efa66 100644
--- a/arch/parisc/include/asm/tlbflush.h
+++ b/arch/parisc/include/asm/tlbflush.h
@@ -85,8 +85,7 @@ static inline void flush_tlb_page(struct vm_area_struct *vma,
         purge_tlb_start(flags);
         mtsp(sid, 1);
         pdtlb(addr);
-        if (unlikely(split_tlb))
-                pitlb(addr);
+        pitlb(addr);
         purge_tlb_end(flags);
 }
 #endif
diff --git a/arch/parisc/kernel/cache.c b/arch/parisc/kernel/cache.c
index 9f1c29d06574..56dc9791ee23 100644
--- a/arch/parisc/kernel/cache.c
+++ b/arch/parisc/kernel/cache.c
@@ -479,18 +479,6 @@ int __flush_tlb_range(unsigned long sid, unsigned long start,
         /* Purge TLB entries for small ranges using the pdtlb and
            pitlb instructions.  These instructions execute locally
            but cause a purge request to be broadcast to other TLBs.  */
-        if (likely(!split_tlb)) {
-                while (start < end) {
-                        purge_tlb_start(flags);
-                        mtsp(sid, 1);
-                        pdtlb(start);
-                        purge_tlb_end(flags);
-                        start += PAGE_SIZE;
-                }
-                return 0;
-        }
-
-        /* split TLB case */
         while (start < end) {
                 purge_tlb_start(flags);
                 mtsp(sid, 1);
diff --git a/arch/parisc/kernel/entry.S b/arch/parisc/kernel/entry.S
index 7c85a91b4710..d3e2633cd688 100644
--- a/arch/parisc/kernel/entry.S
+++ b/arch/parisc/kernel/entry.S
@@ -38,6 +38,7 @@
 #include <asm/ldcw.h>
 #include <asm/traps.h>
 #include <asm/thread_info.h>
+#include <asm/alternative.h>
 
 #include <linux/linkage.h>
 
@@ -464,7 +465,7 @@
         /* Acquire pa_tlb_lock lock and check page is present. */
         .macro          tlb_lock        spc,ptp,pte,tmp,tmp1,fault
 #ifdef CONFIG_SMP
-        cmpib,COND(=),n 0,\spc,2f
+98:     cmpib,COND(=),n 0,\spc,2f
         load_pa_tlb_lock \tmp
 1:      LDCW            0(\tmp),\tmp1
         cmpib,COND(=)   0,\tmp1,1b
@@ -473,6 +474,7 @@
         bb,<,n          \pte,_PAGE_PRESENT_BIT,3f
         b               \fault
         stw,ma          \spc,0(\tmp)
+99:     ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
 2:      LDREG           0(\ptp),\pte
         bb,>=,n         \pte,_PAGE_PRESENT_BIT,\fault
@@ -482,15 +484,17 @@
         /* Release pa_tlb_lock lock without reloading lock address. */
         .macro          tlb_unlock0     spc,tmp
 #ifdef CONFIG_SMP
-        or,COND(=)      %r0,\spc,%r0
+98:     or,COND(=)      %r0,\spc,%r0
         stw,ma          \spc,0(\tmp)
+99:     ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
         .endm
 
         /* Release pa_tlb_lock lock. */
         .macro          tlb_unlock1     spc,tmp
 #ifdef CONFIG_SMP
-        load_pa_tlb_lock \tmp
+98:     load_pa_tlb_lock \tmp
+99:     ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
         tlb_unlock0     \spc,\tmp
 #endif
         .endm
diff --git a/arch/parisc/kernel/pacache.S b/arch/parisc/kernel/pacache.S
index f33bf2d306d6..b41c0136a05f 100644
--- a/arch/parisc/kernel/pacache.S
+++ b/arch/parisc/kernel/pacache.S
@@ -37,6 +37,7 @@
 #include <asm/pgtable.h>
 #include <asm/cache.h>
 #include <asm/ldcw.h>
+#include <asm/alternative.h>
 #include <linux/linkage.h>
 #include <linux/init.h>
 
@@ -190,7 +191,7 @@ ENDPROC_CFI(flush_tlb_all_local)
         .import cache_info,data
 
 ENTRY_CFI(flush_instruction_cache_local)
-        load32          cache_info, %r1
+88:     load32          cache_info, %r1
 
         /* Flush Instruction Cache */
 
@@ -243,6 +244,7 @@ fioneloop2:
 fisync:
         sync
         mtsm            %r22                    /* restore I-bit */
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_ICACHE, INSN_NOP)
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_instruction_cache_local)
@@ -250,7 +252,7 @@ ENDPROC_CFI(flush_instruction_cache_local)
 
         .import cache_info, data
 ENTRY_CFI(flush_data_cache_local)
-        load32          cache_info, %r1
+88:     load32          cache_info, %r1
 
         /* Flush Data Cache */
 
@@ -304,6 +306,7 @@ fdsync:
         syncdma
         sync
         mtsm            %r22                    /* restore I-bit */
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_data_cache_local)
@@ -312,6 +315,7 @@ ENDPROC_CFI(flush_data_cache_local)
 
         .macro  tlb_lock        la,flags,tmp
 #ifdef CONFIG_SMP
+98:
 #if __PA_LDCW_ALIGNMENT > 4
         load32          pa_tlb_lock + __PA_LDCW_ALIGNMENT-1, \la
         depi            0,31,__PA_LDCW_ALIGN_ORDER, \la
@@ -326,15 +330,17 @@ ENDPROC_CFI(flush_data_cache_local)
         nop
         b,n             2b
 3:
+99:     ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
         .endm
 
         .macro  tlb_unlock      la,flags,tmp
 #ifdef CONFIG_SMP
-        ldi             1,\tmp
+98:     ldi             1,\tmp
         sync
         stw             \tmp,0(\la)
         mtsm            \flags
+99:     ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
 #endif
         .endm
 
@@ -596,9 +602,11 @@ ENTRY_CFI(copy_user_page_asm)
         pdtlb,l         %r0(%r29)
 #else
         tlb_lock        %r20,%r21,%r22
-        pdtlb           %r0(%r28)
-        pdtlb           %r0(%r29)
+0:      pdtlb           %r0(%r28)
+1:      pdtlb           %r0(%r29)
         tlb_unlock      %r20,%r21,%r22
+        ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
+        ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SMP, INSN_PxTLB)
 #endif
 
 #ifdef CONFIG_64BIT
@@ -736,8 +744,9 @@ ENTRY_CFI(clear_user_page_asm)
         pdtlb,l         %r0(%r28)
 #else
         tlb_lock        %r20,%r21,%r22
-        pdtlb           %r0(%r28)
+0:      pdtlb           %r0(%r28)
         tlb_unlock      %r20,%r21,%r22
+        ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
 #endif
 
 #ifdef CONFIG_64BIT
@@ -813,11 +822,12 @@ ENTRY_CFI(flush_dcache_page_asm)
         pdtlb,l         %r0(%r28)
 #else
         tlb_lock        %r20,%r21,%r22
-        pdtlb           %r0(%r28)
+0:      pdtlb           %r0(%r28)
         tlb_unlock      %r20,%r21,%r22
+        ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
 #endif
 
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), r31
 
 #ifdef CONFIG_64BIT
@@ -847,6 +857,7 @@ ENTRY_CFI(flush_dcache_page_asm)
         cmpb,COND(<<)   %r28, %r25,1b
         fdc,m           r31(%r28)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
@@ -874,15 +885,19 @@ ENTRY_CFI(flush_icache_page_asm)
 
 #ifdef CONFIG_PA20
         pdtlb,l         %r0(%r28)
-        pitlb,l         %r0(%sr4,%r28)
+1:      pitlb,l         %r0(%sr4,%r28)
+        ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SPLIT_TLB, INSN_NOP)
 #else
         tlb_lock        %r20,%r21,%r22
-        pdtlb           %r0(%r28)
-        pitlb           %r0(%sr4,%r28)
+0:      pdtlb           %r0(%r28)
+1:      pitlb           %r0(%sr4,%r28)
         tlb_unlock      %r20,%r21,%r22
+        ALTERNATIVE(0b, 0b+4, ALT_COND_NO_SMP, INSN_PxTLB)
+        ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SMP, INSN_PxTLB)
+        ALTERNATIVE(1b, 1b+4, ALT_COND_NO_SPLIT_TLB, INSN_NOP)
 #endif
 
-        ldil            L%icache_stride, %r1
+88:     ldil            L%icache_stride, %r1
         ldw             R%icache_stride(%r1), %r31
 
 #ifdef CONFIG_64BIT
@@ -914,13 +929,14 @@ ENTRY_CFI(flush_icache_page_asm)
         cmpb,COND(<<)   %r28, %r25,1b
         fic,m           %r31(%sr4,%r28)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_ICACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_icache_page_asm)
 
 ENTRY_CFI(flush_kernel_dcache_page_asm)
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), %r23
 
 #ifdef CONFIG_64BIT
@@ -950,13 +966,14 @@ ENTRY_CFI(flush_kernel_dcache_page_asm)
         cmpb,COND(<<)           %r26, %r25,1b
         fdc,m           %r23(%r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_kernel_dcache_page_asm)
 
 ENTRY_CFI(purge_kernel_dcache_page_asm)
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), %r23
 
 #ifdef CONFIG_64BIT
@@ -985,13 +1002,14 @@ ENTRY_CFI(purge_kernel_dcache_page_asm)
         cmpb,COND(<<)           %r26, %r25, 1b
         pdc,m           %r23(%r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(purge_kernel_dcache_page_asm)
 
 ENTRY_CFI(flush_user_dcache_range_asm)
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), %r23
         ldo             -1(%r23), %r21
         ANDCM           %r26, %r21, %r26
@@ -999,13 +1017,14 @@ ENTRY_CFI(flush_user_dcache_range_asm)
 1:      cmpb,COND(<<),n %r26, %r25, 1b
         fdc,m           %r23(%sr3, %r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_user_dcache_range_asm)
 
 ENTRY_CFI(flush_kernel_dcache_range_asm)
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), %r23
         ldo             -1(%r23), %r21
         ANDCM           %r26, %r21, %r26
@@ -1014,13 +1033,14 @@ ENTRY_CFI(flush_kernel_dcache_range_asm)
         fdc,m           %r23(%r26)
 
         sync
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         syncdma
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_kernel_dcache_range_asm)
 
 ENTRY_CFI(purge_kernel_dcache_range_asm)
-        ldil            L%dcache_stride, %r1
+88:     ldil            L%dcache_stride, %r1
         ldw             R%dcache_stride(%r1), %r23
         ldo             -1(%r23), %r21
         ANDCM           %r26, %r21, %r26
@@ -1029,13 +1049,14 @@ ENTRY_CFI(purge_kernel_dcache_range_asm)
         pdc,m           %r23(%r26)
 
         sync
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_DCACHE, INSN_NOP)
         syncdma
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(purge_kernel_dcache_range_asm)
 
 ENTRY_CFI(flush_user_icache_range_asm)
-        ldil            L%icache_stride, %r1
+88:     ldil            L%icache_stride, %r1
         ldw             R%icache_stride(%r1), %r23
         ldo             -1(%r23), %r21
         ANDCM           %r26, %r21, %r26
@@ -1043,13 +1064,14 @@ ENTRY_CFI(flush_user_icache_range_asm)
 1:      cmpb,COND(<<),n %r26, %r25,1b
         fic,m           %r23(%sr3, %r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_ICACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_user_icache_range_asm)
 
 ENTRY_CFI(flush_kernel_icache_page)
-        ldil            L%icache_stride, %r1
+88:     ldil            L%icache_stride, %r1
         ldw             R%icache_stride(%r1), %r23
 
 #ifdef CONFIG_64BIT
@@ -1079,13 +1101,14 @@ ENTRY_CFI(flush_kernel_icache_page)
         cmpb,COND(<<)           %r26, %r25, 1b
         fic,m           %r23(%sr4, %r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_ICACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
 ENDPROC_CFI(flush_kernel_icache_page)
 
 ENTRY_CFI(flush_kernel_icache_range_asm)
-        ldil            L%icache_stride, %r1
+88:     ldil            L%icache_stride, %r1
         ldw             R%icache_stride(%r1), %r23
         ldo             -1(%r23), %r21
         ANDCM           %r26, %r21, %r26
@@ -1093,6 +1116,7 @@ ENTRY_CFI(flush_kernel_icache_range_asm)
 1:      cmpb,COND(<<),n %r26, %r25, 1b
         fic,m           %r23(%sr4, %r26)
 
+89:     ALTERNATIVE(88b, 89b, ALT_COND_NO_ICACHE, INSN_NOP)
         sync
         bv              %r0(%r2)
         nop
diff --git a/arch/parisc/kernel/setup.c b/arch/parisc/kernel/setup.c
index 4e87c35c22b7..db6e7957f9a3 100644
--- a/arch/parisc/kernel/setup.c
+++ b/arch/parisc/kernel/setup.c
@@ -305,6 +305,86 @@ static int __init parisc_init_resources(void)
         return 0;
 }
 
+static int no_alternatives __initdata;
+static int __init setup_no_alternatives(char *str)
+{
+        no_alternatives = 1;
+        return 1;
+}
+__setup("no-alternatives", setup_no_alternatives);
+
+static void __init apply_alternatives_all(void)
+{
+        struct alt_instr *entry;
+        int index = 0, applied = 0;
+
+
+        pr_info("alternatives: %spatching kernel code\n",
+                no_alternatives ? "NOT " : "");
+        if (no_alternatives)
+                return;
+
+        set_kernel_text_rw(1);
+
+        for (entry = (struct alt_instr *) &__alt_instructions;
+                entry < (struct alt_instr *) &__alt_instructions_end;
+                entry++, index++) {
+
+                u32 *from, len, cond, replacement;
+
+                from = (u32 *)((ulong)&entry->orig_offset + entry->orig_offset);
+                len = entry->len;
+                cond = entry->cond;
+                replacement = entry->replacement;
+
+                WARN_ON(!cond);
+                pr_debug("Check %d: Cond 0x%x, Replace %02d instructions @ 0x%px with 0x%08x\n",
+                        index, cond, len, from, replacement);
+
+                if ((cond & ALT_COND_NO_SMP) && (num_online_cpus() != 1))
+                        continue;
+                if ((cond & ALT_COND_NO_DCACHE) && (cache_info.dc_size != 0))
+                        continue;
+                if ((cond & ALT_COND_NO_ICACHE) && (cache_info.ic_size != 0))
+                        continue;
+
+                /*
+                 * If the PDC_MODEL capabilities has Non-coherent IO-PDIR bit
+                 * set (bit #61, big endian), we have to flush and sync every
+                 * time IO-PDIR is changed in Ike/Astro.
+                 */
+                if ((cond & ALT_COND_NO_IOC_FDC) &&
+                        (boot_cpu_data.pdc.capabilities & PDC_MODEL_IOPDIR_FDC))
+                        continue;
+
+                /* Want to replace pdtlb by a pdtlb,l instruction? */
+                if (replacement == INSN_PxTLB) {
+                        replacement = *from;
+                        if (boot_cpu_data.cpu_type >= pcxu) /* >= pa2.0 ? */
+                                replacement |= (1 << 10); /* set el bit */
+                }
+
+                /*
+                 * Replace instruction with NOPs?
+                 * For long distance insert a branch instruction instead.
+                 */
+                if (replacement == INSN_NOP && len > 1)
+                        replacement = 0xe8000002 + (len-2)*8; /* "b,n .+8" */
+
+                pr_debug("Do    %d: Cond 0x%x, Replace %02d instructions @ 0x%px with 0x%08x\n",
+                        index, cond, len, from, replacement);
+
+                /* Replace instruction */
+                *from = replacement;
+                applied++;
+        }
+
+        pr_info("alternatives: applied %d out of %d patches\n", applied, index);
+
+        set_kernel_text_rw(0);
+}
+
+
 extern void gsc_init(void);
 extern void processor_init(void);
 extern void ccio_init(void);
@@ -346,6 +426,7 @@ static int __init parisc_init(void)
                         boot_cpu_data.cpu_hz / 1000000,
                         boot_cpu_data.cpu_hz % 1000000  );
 
+        apply_alternatives_all();
         parisc_setup_cache_timing();
 
         /* These are in a non-obvious order, will fix when we have an iotree */
diff --git a/arch/parisc/kernel/signal.c b/arch/parisc/kernel/signal.c
index 342073f44d3f..848c1934680b 100644
--- a/arch/parisc/kernel/signal.c
+++ b/arch/parisc/kernel/signal.c
@@ -65,7 +65,6 @@
 #define INSN_LDI_R25_1   0x34190002 /* ldi  1,%r25 (in_syscall=1) */
 #define INSN_LDI_R20     0x3414015a /* ldi  __NR_rt_sigreturn,%r20 */
 #define INSN_BLE_SR2_R0  0xe4008200 /* be,l 0x100(%sr2,%r0),%sr0,%r31 */
-#define INSN_NOP         0x08000240 /* nop */
 /* For debugging */
 #define INSN_DIE_HORRIBLY 0x68000ccc /* stw %r0,0x666(%sr0,%r0) */
 
diff --git a/arch/parisc/kernel/vmlinux.lds.S b/arch/parisc/kernel/vmlinux.lds.S
index da2e31190efa..c3b1b9c24ede 100644
--- a/arch/parisc/kernel/vmlinux.lds.S
+++ b/arch/parisc/kernel/vmlinux.lds.S
@@ -61,6 +61,12 @@ SECTIONS
                 EXIT_DATA
         }
         PERCPU_SECTION(8)
+        . = ALIGN(4);
+        .altinstructions : {
+                __alt_instructions = .;
+                *(.altinstructions)
+                __alt_instructions_end = .;
+        }
         . = ALIGN(HUGEPAGE_SIZE);
         __init_end = .;
         /* freed after init ends here */
diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
index aae9b0d71c1e..e7e626bcd0be 100644
--- a/arch/parisc/mm/init.c
+++ b/arch/parisc/mm/init.c
@@ -511,6 +511,21 @@ static void __init map_pages(unsigned long start_vaddr,
         }
 }
 
+void __init set_kernel_text_rw(int enable_read_write)
+{
+        unsigned long start = (unsigned long)_stext;
+        unsigned long end   = (unsigned long)_etext;
+
+        map_pages(start, __pa(start), end-start,
+                PAGE_KERNEL_RWX, enable_read_write ? 1:0);
+
+        /* force the kernel to see the new TLB entries */
+        __flush_tlb_range(0, start, end);
+
+        /* dump old cached instructions */
+        flush_icache_range(start, end);
+}
+
 void __ref free_initmem(void)
 {
         unsigned long init_begin = (unsigned long)__init_begin;
diff --git a/drivers/parisc/ccio-dma.c b/drivers/parisc/ccio-dma.c
index 614823617b8b..701a7d6a74d5 100644
--- a/drivers/parisc/ccio-dma.c
+++ b/drivers/parisc/ccio-dma.c
@@ -609,14 +609,13 @@ ccio_io_pdir_entry(u64 *pdir_ptr, space_t sid, unsigned long vba,
         **        PCX-T'? Don't know. (eg C110 or similar K-class)
         **
         ** See PDC_MODEL/option 0/SW_CAP word for "Non-coherent IO-PDIR bit".
-        ** Hopefully we can patch (NOP) these out at boot time somehow.
         **
         ** "Since PCX-U employs an offset hash that is incompatible with
         ** the real mode coherence index generation of U2, the PDIR entry
         ** must be flushed to memory to retain coherence."
         */
-        asm volatile("fdc %%r0(%0)" : : "r" (pdir_ptr));
-        asm volatile("sync");
+        asm_io_fdc(pdir_ptr);
+        asm_io_sync();
 }
 
 /**
@@ -682,17 +681,14 @@ ccio_mark_invalid(struct ioc *ioc, dma_addr_t iova, size_t byte_cnt)
                 ** FIXME: PCX_W platforms don't need FDC/SYNC. (eg C360)
                 **   PCX-U/U+ do. (eg C200/C240)
                 ** See PDC_MODEL/option 0/SW_CAP for "Non-coherent IO-PDIR bit".
-                **
-                ** Hopefully someone figures out how to patch (NOP) the
-                ** FDC/SYNC out at boot time.
                 */
-                asm volatile("fdc %%r0(%0)" : : "r" (pdir_ptr[7]));
+                asm_io_fdc(pdir_ptr);
 
                 iovp     += IOVP_SIZE;
                 byte_cnt -= IOVP_SIZE;
         }
 
-        asm volatile("sync");
+        asm_io_sync();
         ccio_clear_io_tlb(ioc, CCIO_IOVP(iova), saved_byte_cnt);
 }
 
diff --git a/drivers/parisc/sba_iommu.c b/drivers/parisc/sba_iommu.c
index 11de0eccf968..c1e599a429af 100644
--- a/drivers/parisc/sba_iommu.c
+++ b/drivers/parisc/sba_iommu.c
@@ -587,8 +587,7 @@ sba_io_pdir_entry(u64 *pdir_ptr, space_t sid, unsigned long vba,
          * (bit #61, big endian), we have to flush and sync every time
          * IO-PDIR is changed in Ike/Astro.
          */
-        if (ioc_needs_fdc)
-                asm volatile("fdc %%r0(%0)" : : "r" (pdir_ptr));
+        asm_io_fdc(pdir_ptr);
 }
 
 
@@ -641,8 +640,8 @@ sba_mark_invalid(struct ioc *ioc, dma_addr_t iova, size_t byte_cnt)
                 do {
                         /* clear I/O Pdir entry "valid" bit first */
                         ((u8 *) pdir_ptr)[7] = 0;
+                        asm_io_fdc(pdir_ptr);
                         if (ioc_needs_fdc) {
-                                asm volatile("fdc %%r0(%0)" : : "r" (pdir_ptr));
 #if 0
                                 entries_per_cacheline = L1_CACHE_SHIFT - 3;
 #endif
@@ -661,8 +660,7 @@ sba_mark_invalid(struct ioc *ioc, dma_addr_t iova, size_t byte_cnt)
         ** could dump core on HPMC.
         */
         ((u8 *) pdir_ptr)[7] = 0;
-        if (ioc_needs_fdc)
-                asm volatile("fdc %%r0(%0)" : : "r" (pdir_ptr));
+        asm_io_fdc(pdir_ptr);
 
         WRITE_REG( SBA_IOVA(ioc, iovp, 0, 0), ioc->ioc_hpa+IOC_PCOM);
 }
@@ -773,8 +771,7 @@ sba_map_single(struct device *dev, void *addr, size_t size,
         }
 
         /* force FDC ops in io_pdir_entry() to be visible to IOMMU */
-        if (ioc_needs_fdc)
-                asm volatile("sync" : : );
+        asm_io_sync();
 
 #ifdef ASSERT_PDIR_SANITY
         sba_check_pdir(ioc,"Check after sba_map_single()");
@@ -858,8 +855,7 @@ sba_unmap_page(struct device *dev, dma_addr_t iova, size_t size,
         sba_free_range(ioc, iova, size);
 
         /* If fdc's were issued, force fdc's to be visible now */
-        if (ioc_needs_fdc)
-                asm volatile("sync" : : );
+        asm_io_sync();
 
         READ_REG(ioc->ioc_hpa+IOC_PCOM);        /* flush purges */
 #endif /* DELAYED_RESOURCE_CNT == 0 */
@@ -1008,8 +1004,7 @@ sba_map_sg(struct device *dev, struct scatterlist *sglist, int nents,
         filled = iommu_fill_pdir(ioc, sglist, nents, 0, sba_io_pdir_entry);
 
         /* force FDC ops in io_pdir_entry() to be visible to IOMMU */
-        if (ioc_needs_fdc)
-                asm volatile("sync" : : );
+        asm_io_sync();
 
 #ifdef ASSERT_PDIR_SANITY
         if (sba_check_pdir(ioc,"Check after sba_map_sg()"))