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Subject[patch 09/13] 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>

Index: linux-2.6-x86.git/arch/x86/mm/pat.c
===================================================================
--- linux-2.6-x86.git.orig/arch/x86/mm/pat.c 2008-03-18 03:33:01.000000000 -0700
+++ linux-2.6-x86.git/arch/x86/mm/pat.c 2008-03-18 09:20:21.000000000 -0700
@@ -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;

@@ -195,6 +197,21 @@
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)
{
@@ -205,9 +222,14 @@

/* 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;
}

@@ -219,8 +241,29 @@
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;
@@ -401,7 +444,14 @@
}


-/* /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)
{
@@ -411,10 +461,13 @@
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
@@ -432,10 +485,65 @@
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);
+}
+
Index: linux-2.6-x86.git/drivers/char/mem.c
===================================================================
--- linux-2.6-x86.git.orig/drivers/char/mem.c 2008-03-18 03:33:01.000000000 -0700
+++ linux-2.6-x86.git/drivers/char/mem.c 2008-03-18 03:38:05.000000000 -0700
@@ -300,6 +300,35 @@
}
#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 @@
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;
}

--


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