x86: PAT use reserve free memtype in mmap of /dev/mem

Use reserve_memtype and free_memtype wrappers for /dev/mem mmaps. The memtype
is slightly complicated here, given that we have to support existing X mappings.
We fallback on UC_MINUS for that.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 152 insertions, 11 deletions

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 64cc0c18233e..1489aafbfa71 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -11,6 +11,7 @@
 #include <linux/kernel.h>
 #include <linux/gfp.h>
 #include <linux/fs.h>
+#include <linux/bootmem.h>
 
 #include <asm/msr.h>
 #include <asm/tlbflush.h>
@@ -21,6 +22,7 @@
 #include <asm/cacheflush.h>
 #include <asm/fcntl.h>
 #include <asm/mtrr.h>
+#include <asm/io.h>
 
 int pat_wc_enabled = 1;
 
@@ -190,6 +192,21 @@ static int pat_x_mtrr_type(u64 start, u64 end, unsigned long prot,
         return 0;
 }
 
+/*
+ * req_type typically has one of the:
+ * - _PAGE_CACHE_WB
+ * - _PAGE_CACHE_WC
+ * - _PAGE_CACHE_UC_MINUS
+ * - _PAGE_CACHE_UC
+ *
+ * req_type will have a special case value '-1', when requester want to inherit
+ * the memory type from mtrr (if WB), existing PAT, defaulting to UC_MINUS.
+ *
+ * If ret_type is NULL, function will return an error if it cannot reserve the
+ * region with req_type. If ret_type is non-null, function will return
+ * available type in ret_type in case of no error. In case of any error
+ * it will return a negative return value.
+ */
 int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                         unsigned long *ret_type)
 {
@@ -200,9 +217,14 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
 
         /* Only track when pat_wc_enabled */
         if (!pat_wc_enabled) {
-                if (ret_type)
-                        *ret_type = req_type;
-
+                /* This is identical to page table setting without PAT */
+                if (ret_type) {
+                        if (req_type == -1) {
+                                *ret_type = _PAGE_CACHE_WB;
+                        } else {
+                                *ret_type = req_type;
+                        }
+                }
                 return 0;
         }
 
@@ -214,8 +236,29 @@ int reserve_memtype(u64 start, u64 end, unsigned long req_type,
                 return 0;
         }
 
-        req_type &= _PAGE_CACHE_MASK;
-        err = pat_x_mtrr_type(start, end, req_type, &actual_type);
+        if (req_type == -1) {
+                /*
+                 * Special case where caller wants to inherit from mtrr or
+                 * existing pat mapping, defaulting to UC_MINUS in case of
+                 * no match.
+                 */
+                u8 mtrr_type = mtrr_type_lookup(start, end);
+                if (mtrr_type == 0xFE) { /* MTRR match error */
+                        err = -1;
+                }
+
+                if (mtrr_type == MTRR_TYPE_WRBACK) {
+                        req_type = _PAGE_CACHE_WB;
+                        actual_type = _PAGE_CACHE_WB;
+                } else {
+                        req_type = _PAGE_CACHE_UC_MINUS;
+                        actual_type = _PAGE_CACHE_UC_MINUS;
+                }
+        } else {
+                req_type &= _PAGE_CACHE_MASK;
+                err = pat_x_mtrr_type(start, end, req_type, &actual_type);
+        }
+
         if (err) {
                 if (ret_type)
                         *ret_type = actual_type;
@@ -420,7 +463,14 @@ int free_memtype(u64 start, u64 end)
 }
 
 
-/* /dev/mem interface. Use the previous mapping */
+/*
+ * /dev/mem mmap interface. The memtype used for mapping varies:
+ * - Use UC for mappings with O_SYNC flag
+ * - Without O_SYNC flag, if there is any conflict in reserve_memtype,
+ *   inherit the memtype from existing mapping.
+ * - Else use UC_MINUS memtype (for backward compatibility with existing
+ *   X drivers.
+ */
 pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
                                 unsigned long size, pgprot_t vma_prot)
 {
@@ -430,10 +480,13 @@ pgprot_t phys_mem_access_prot(struct file *file, unsigned long pfn,
 int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
                                 unsigned long size, pgprot_t *vma_prot)
 {
+        u64 offset = ((u64) pfn) << PAGE_SHIFT;
+        unsigned long flags = _PAGE_CACHE_UC_MINUS;
+        unsigned long ret_flags;
+        int retval;
 
         if (file->f_flags & O_SYNC) {
-                *vma_prot = pgprot_noncached(*vma_prot);
-                return 1;
+                flags = _PAGE_CACHE_UC;
         }
 
 #ifdef CONFIG_X86_32
@@ -451,10 +504,65 @@ int phys_mem_access_prot_allowed(struct file *file, unsigned long pfn,
                 test_bit(X86_FEATURE_CYRIX_ARR, boot_cpu_data.x86_capability) ||
                 test_bit(X86_FEATURE_CENTAUR_MCR, boot_cpu_data.x86_capability)) &&
            (pfn << PAGE_SHIFT) >= __pa(high_memory)) {
-                *vma_prot = pgprot_noncached(*vma_prot);
-                return 1;
+                flags = _PAGE_CACHE_UC;
         }
 #endif
 
+        /*
+         * With O_SYNC, we can only take UC mapping. Fail if we cannot.
+         * Without O_SYNC, we want to get
+         * - WB for WB-able memory and no other conflicting mappings
+         * - UC_MINUS for non-WB-able memory with no other conflicting mappings
+         * - Inherit from confliting mappings otherwise
+         */
+        if (flags != _PAGE_CACHE_UC_MINUS) {
+                retval = reserve_memtype(offset, offset + size, flags, NULL);
+        } else {
+                retval = reserve_memtype(offset, offset + size, -1, &ret_flags);
+        }
+
+        if (retval < 0)
+                return 0;
+
+        flags = ret_flags;
+
+        if (pfn <= max_pfn_mapped &&
+            ioremap_change_attr((unsigned long)__va(offset), size, flags) < 0) {
+                free_memtype(offset, offset + size);
+                printk(KERN_DEBUG
+                "%s:%d /dev/mem ioremap_change_attr failed %s for %Lx-%Lx\n",
+                        current->comm, current->pid,
+                        cattr_name(flags),
+                        offset, offset + size);
+                return 0;
+        }
+
+        *vma_prot = __pgprot((pgprot_val(*vma_prot) & ~_PAGE_CACHE_MASK) |
+                             flags);
         return 1;
 }
+
+void map_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
+{
+        u64 addr = (u64)pfn << PAGE_SHIFT;
+        unsigned long flags;
+        unsigned long want_flags = (pgprot_val(vma_prot) & _PAGE_CACHE_MASK);
+
+        reserve_memtype(addr, addr + size, want_flags, &flags);
+        if (flags != want_flags) {
+                printk(KERN_DEBUG
+                "%s:%d /dev/mem expected mapping type %s for %Lx-%Lx, got %s\n",
+                        current->comm, current->pid,
+                        cattr_name(want_flags),
+                        addr, addr + size,
+                        cattr_name(flags));
+        }
+}
+
+void unmap_devmem(unsigned long pfn, unsigned long size, pgprot_t vma_prot)
+{
+        u64 addr = (u64)pfn << PAGE_SHIFT;
+
+        free_memtype(addr, addr + size);
+}
+
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index 56b2fb4fbc93..e83623ead441 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -300,6 +300,35 @@ static inline int private_mapping_ok(struct vm_area_struct *vma)
 }
 #endif
 
+void __attribute__((weak))
+map_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
+{
+        /* nothing. architectures can override. */
+}
+
+void __attribute__((weak))
+unmap_devmem(unsigned long pfn, unsigned long len, pgprot_t prot)
+{
+        /* nothing. architectures can override. */
+}
+
+static void mmap_mem_open(struct vm_area_struct *vma)
+{
+        map_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
+                        vma->vm_page_prot);
+}
+
+static void mmap_mem_close(struct vm_area_struct *vma)
+{
+        unmap_devmem(vma->vm_pgoff,  vma->vm_end - vma->vm_start,
+                        vma->vm_page_prot);
+}
+
+static struct vm_operations_struct mmap_mem_ops = {
+        .open  = mmap_mem_open,
+        .close = mmap_mem_close
+};
+
 static int mmap_mem(struct file * file, struct vm_area_struct * vma)
 {
         size_t size = vma->vm_end - vma->vm_start;
@@ -321,13 +350,17 @@ static int mmap_mem(struct file * file, struct vm_area_struct * vma)
                                                  size,
                                                  vma->vm_page_prot);
 
+        vma->vm_ops = &mmap_mem_ops;
+
         /* Remap-pfn-range will mark the range VM_IO and VM_RESERVED */
         if (remap_pfn_range(vma,
                             vma->vm_start,
                             vma->vm_pgoff,
                             size,
-                            vma->vm_page_prot))
+                            vma->vm_page_prot)) {
+                unmap_devmem(vma->vm_pgoff, size, vma->vm_page_prot);
                 return -EAGAIN;
+        }
         return 0;
 }