KVM: ia64: Drop in SN2 replacement of fast path ITC emulation fault handler

Copy in SN2 RTC based ITC emulation for fast exit. The two versions
have the same size, so a dropin is simpler than patching the branch
instruction to hit the SN2 version.

Signed-off-by: Jes Sorensen <jes@sgi.com>
Acked-by: Xiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

4 files changed, 71 insertions, 5 deletions

diff --git a/arch/ia64/include/asm/kvm_host.h b/arch/ia64/include/asm/kvm_host.h
index 12439956551b..589536fa799d 100644
--- a/arch/ia64/include/asm/kvm_host.h
+++ b/arch/ia64/include/asm/kvm_host.h
@@ -580,6 +580,8 @@ struct kvm_vmm_info{
         kvm_vmm_entry   *vmm_entry;
         kvm_tramp_entry *tramp_entry;
         unsigned long   vmm_ivt;
+        unsigned long   patch_mov_ar;
+        unsigned long   patch_mov_ar_sn2;
 };
 
 int kvm_highest_pending_irq(struct kvm_vcpu *vcpu);
diff --git a/arch/ia64/kvm/kvm-ia64.c b/arch/ia64/kvm/kvm-ia64.c
index ebbd995194fb..4623a90e515a 100644
--- a/arch/ia64/kvm/kvm-ia64.c
+++ b/arch/ia64/kvm/kvm-ia64.c
@@ -1671,8 +1671,37 @@ out:
         return 0;
 }
 
+
+/*
+ * On SN2, the ITC isn't stable, so copy in fast path code to use the
+ * SN2 RTC, replacing the ITC based default verion.
+ */
+static void kvm_patch_vmm(struct kvm_vmm_info *vmm_info,
+                          struct module *module)
+{
+        unsigned long new_ar, new_ar_sn2;
+        unsigned long module_base;
+
+        if (!ia64_platform_is("sn2"))
+                return;
+
+        module_base = (unsigned long)module->module_core;
+
+        new_ar = kvm_vmm_base + vmm_info->patch_mov_ar - module_base;
+        new_ar_sn2 = kvm_vmm_base + vmm_info->patch_mov_ar_sn2 - module_base;
+
+        printk(KERN_INFO "kvm: Patching ITC emulation to use SGI SN2 RTC "
+               "as source\n");
+
+        /*
+         * Copy the SN2 version of mov_ar into place. They are both
+         * the same size, so 6 bundles is sufficient (6 * 0x10).
+         */
+        memcpy((void *)new_ar, (void *)new_ar_sn2, 0x60);
+}
+
 static int kvm_relocate_vmm(struct kvm_vmm_info *vmm_info,
-                                                struct module *module)
+                            struct module *module)
 {
         unsigned long module_base;
         unsigned long vmm_size;
@@ -1694,6 +1723,7 @@ static int kvm_relocate_vmm(struct kvm_vmm_info *vmm_info,
                 return -EFAULT;
 
         memcpy((void *)kvm_vmm_base, (void *)module_base, vmm_size);
+        kvm_patch_vmm(vmm_info, module);
         kvm_flush_icache(kvm_vmm_base, vmm_size);
 
         /*Recalculate kvm_vmm_info based on new VMM*/
diff --git a/arch/ia64/kvm/optvfault.S b/arch/ia64/kvm/optvfault.S
index 32254ce9a1bd..f793be3effff 100644
--- a/arch/ia64/kvm/optvfault.S
+++ b/arch/ia64/kvm/optvfault.S
@@ -11,6 +11,7 @@
 
 #include <asm/asmmacro.h>
 #include <asm/processor.h>
+#include <asm/kvm_host.h>
 
 #include "vti.h"
 #include "asm-offsets.h"
@@ -140,6 +141,35 @@ GLOBAL_ENTRY(kvm_asm_mov_from_ar)
         ;;
 END(kvm_asm_mov_from_ar)
 
+/*
+ * Special SGI SN2 optimized version of mov_from_ar using the SN2 RTC
+ * clock as it's source for emulating the ITC. This version will be
+ * copied on top of the original version if the host is determined to
+ * be an SN2.
+ */
+GLOBAL_ENTRY(kvm_asm_mov_from_ar_sn2)
+        add r18=VMM_VCPU_ITC_OFS_OFFSET, r21
+        movl r19 = (KVM_VMM_BASE+(1<<KVM_VMM_SHIFT))
+
+        add r16=VMM_VCPU_LAST_ITC_OFFSET,r21
+        extr.u r17=r25,6,7
+        mov r24=b0
+        ;;
+        ld8 r18=[r18]
+        ld8 r19=[r19]
+        addl r20=@gprel(asm_mov_to_reg),gp
+        ;;
+        add r19=r19,r18
+        shladd r17=r17,4,r20
+        ;;
+        adds r30=kvm_resume_to_guest-asm_mov_to_reg,r20
+        st8 [r16] = r19
+        mov b0=r17
+        br.sptk.few b0
+        ;;
+END(kvm_asm_mov_from_ar_sn2)
+
+
 
 // mov r1=rr[r3]
 GLOBAL_ENTRY(kvm_asm_mov_from_rr)
diff --git a/arch/ia64/kvm/vmm.c b/arch/ia64/kvm/vmm.c
index 9eee5c04bacc..f4b4c899bb6c 100644
--- a/arch/ia64/kvm/vmm.c
+++ b/arch/ia64/kvm/vmm.c
@@ -30,15 +30,19 @@ MODULE_AUTHOR("Intel");
 MODULE_LICENSE("GPL");
 
 extern char kvm_ia64_ivt;
+extern char kvm_asm_mov_from_ar;
+extern char kvm_asm_mov_from_ar_sn2;
 extern fpswa_interface_t *vmm_fpswa_interface;
 
 long vmm_sanity = 1;
 
 struct kvm_vmm_info vmm_info = {
-        .module      = THIS_MODULE,
-        .vmm_entry   = vmm_entry,
-        .tramp_entry = vmm_trampoline,
-        .vmm_ivt     = (unsigned long)&kvm_ia64_ivt,
+        .module                 = THIS_MODULE,
+        .vmm_entry              = vmm_entry,
+        .tramp_entry            = vmm_trampoline,
+        .vmm_ivt                = (unsigned long)&kvm_ia64_ivt,
+        .patch_mov_ar           = (unsigned long)&kvm_asm_mov_from_ar,
+        .patch_mov_ar_sn2       = (unsigned long)&kvm_asm_mov_from_ar_sn2,
 };
 
 static int __init  kvm_vmm_init(void)