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>

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index 64cc0c1..1489aaf 100644 (file)
--- 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 56b2fb4..e83623e 100644 (file)
--- 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;
 }