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x86: a new API for drivers/etc to control cache and other page attrib…
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…utes

Right now, if drivers or other code want to change, say, a cache attribute of a
page, the only API they have is change_page_attr(). c-p-a is a really bad API
for this, because it forces the caller to know *ALL* the attributes he wants
for the page, not just the 1 thing he wants to change. So code that wants to
set a page uncachable, needs to be aware of the NX status as well etc etc etc.

This patch introduces a set of new APIs for this, set_pages_<attr> and
set_memory_<attr>, that offer a logical change to the user, and leave all
attributes not implied by the requested logical change alone.

Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Arjan van de Ven authored and Ingo Molnar committed Jan 30, 2008
1 parent e81d5dc commit 75cbade
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197 changes: 197 additions & 0 deletions arch/x86/mm/pageattr.c
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Original file line number Diff line number Diff line change
Expand Up @@ -211,6 +211,8 @@ __change_page_attr(unsigned long address, unsigned long pfn, pgprot_t prot)
* mem_map entry (pfn_valid() is false).
*
* See change_page_attr() documentation for more details.
*
* Modules and drivers should use the set_memory_* APIs instead.
*/

int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
Expand Down Expand Up @@ -273,6 +275,8 @@ int change_page_attr_addr(unsigned long address, int numpages, pgprot_t prot)
* (e.g. in user space) * This function only deals with the kernel linear map.
*
* For MMIO areas without mem_map use change_page_attr_addr() instead.
*
* Modules and drivers should use the set_pages_* APIs instead.
*/
int change_page_attr(struct page *page, int numpages, pgprot_t prot)
{
Expand All @@ -282,6 +286,199 @@ int change_page_attr(struct page *page, int numpages, pgprot_t prot)
}
EXPORT_SYMBOL(change_page_attr);

/**
* change_page_attr_set - Change page table attributes in the linear mapping.
* @addr: Virtual address in linear mapping.
* @numpages: Number of pages to change
* @prot: Protection/caching type bits to set (PAGE_*)
*
* Returns 0 on success, otherwise a negated errno.
*
* This should be used when a page is mapped with a different caching policy
* than write-back somewhere - some CPUs do not like it when mappings with
* different caching policies exist. This changes the page attributes of the
* in kernel linear mapping too.
*
* Caller must call global_flush_tlb() later to make the changes active.
*
* The caller needs to ensure that there are no conflicting mappings elsewhere
* (e.g. in user space) * This function only deals with the kernel linear map.
*
* This function is different from change_page_attr() in that only selected bits
* are impacted, all other bits remain as is.
*/
int change_page_attr_set(unsigned long addr, int numpages, pgprot_t prot)
{
pgprot_t current_prot;
int level;
pte_t *pte;

pte = lookup_address(addr, &level);
if (pte)
current_prot = pte_pgprot(*pte);
else
pgprot_val(current_prot) = 0;

pgprot_val(prot) = pgprot_val(current_prot) | pgprot_val(prot);

return change_page_attr_addr(addr, numpages, prot);
}

/**
* change_page_attr_clear - Change page table attributes in the linear mapping.
* @addr: Virtual address in linear mapping.
* @numpages: Number of pages to change
* @prot: Protection/caching type bits to clear (PAGE_*)
*
* Returns 0 on success, otherwise a negated errno.
*
* This should be used when a page is mapped with a different caching policy
* than write-back somewhere - some CPUs do not like it when mappings with
* different caching policies exist. This changes the page attributes of the
* in kernel linear mapping too.
*
* Caller must call global_flush_tlb() later to make the changes active.
*
* The caller needs to ensure that there are no conflicting mappings elsewhere
* (e.g. in user space) * This function only deals with the kernel linear map.
*
* This function is different from change_page_attr() in that only selected bits
* are impacted, all other bits remain as is.
*/
int change_page_attr_clear(unsigned long addr, int numpages, pgprot_t prot)
{
pgprot_t current_prot;
int level;
pte_t *pte;

pte = lookup_address(addr, &level);
if (pte)
current_prot = pte_pgprot(*pte);
else
pgprot_val(current_prot) = 0;

pgprot_val(prot) = pgprot_val(current_prot) & ~pgprot_val(prot);

return change_page_attr_addr(addr, numpages, prot);
}



int set_memory_uc(unsigned long addr, int numpages)
{
pgprot_t uncached;

pgprot_val(uncached) = _PAGE_PCD | _PAGE_PWT;
return change_page_attr_set(addr, numpages, uncached);
}
EXPORT_SYMBOL(set_memory_uc);

int set_memory_wb(unsigned long addr, int numpages)
{
pgprot_t uncached;

pgprot_val(uncached) = _PAGE_PCD | _PAGE_PWT;
return change_page_attr_clear(addr, numpages, uncached);
}
EXPORT_SYMBOL(set_memory_wb);

int set_memory_x(unsigned long addr, int numpages)
{
pgprot_t nx;

pgprot_val(nx) = _PAGE_NX;
return change_page_attr_clear(addr, numpages, nx);
}
EXPORT_SYMBOL(set_memory_x);

int set_memory_nx(unsigned long addr, int numpages)
{
pgprot_t nx;

pgprot_val(nx) = _PAGE_NX;
return change_page_attr_set(addr, numpages, nx);
}
EXPORT_SYMBOL(set_memory_nx);

int set_memory_ro(unsigned long addr, int numpages)
{
pgprot_t rw;

pgprot_val(rw) = _PAGE_RW;
return change_page_attr_clear(addr, numpages, rw);
}
EXPORT_SYMBOL(set_memory_ro);

int set_memory_rw(unsigned long addr, int numpages)
{
pgprot_t rw;

pgprot_val(rw) = _PAGE_RW;
return change_page_attr_set(addr, numpages, rw);
}
EXPORT_SYMBOL(set_memory_rw);

int set_pages_uc(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t uncached;

pgprot_val(uncached) = _PAGE_PCD | _PAGE_PWT;
return change_page_attr_set(addr, numpages, uncached);
}
EXPORT_SYMBOL(set_pages_uc);

int set_pages_wb(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t uncached;

pgprot_val(uncached) = _PAGE_PCD | _PAGE_PWT;
return change_page_attr_clear(addr, numpages, uncached);
}
EXPORT_SYMBOL(set_pages_wb);

int set_pages_x(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t nx;

pgprot_val(nx) = _PAGE_NX;
return change_page_attr_clear(addr, numpages, nx);
}
EXPORT_SYMBOL(set_pages_x);

int set_pages_nx(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t nx;

pgprot_val(nx) = _PAGE_NX;
return change_page_attr_set(addr, numpages, nx);
}
EXPORT_SYMBOL(set_pages_nx);

int set_pages_ro(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t rw;

pgprot_val(rw) = _PAGE_RW;
return change_page_attr_clear(addr, numpages, rw);
}
EXPORT_SYMBOL(set_pages_ro);

int set_pages_rw(struct page *page, int numpages)
{
unsigned long addr = (unsigned long)page_address(page);
pgprot_t rw;

pgprot_val(rw) = _PAGE_RW;
return change_page_attr_set(addr, numpages, rw);
}
EXPORT_SYMBOL(set_pages_rw);


void clflush_cache_range(void *addr, int size)
{
int i;
Expand Down
15 changes: 15 additions & 0 deletions include/asm-x86/cacheflush.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -27,6 +27,21 @@
void global_flush_tlb(void);
int change_page_attr(struct page *page, int numpages, pgprot_t prot);
int change_page_attr_addr(unsigned long addr, int numpages, pgprot_t prot);

int set_pages_uc(struct page *page, int numpages);
int set_pages_wb(struct page *page, int numpages);
int set_pages_x(struct page *page, int numpages);
int set_pages_nx(struct page *page, int numpages);
int set_pages_ro(struct page *page, int numpages);
int set_pages_rw(struct page *page, int numpages);

int set_memory_uc(unsigned long addr, int numpages);
int set_memory_wb(unsigned long addr, int numpages);
int set_memory_x(unsigned long addr, int numpages);
int set_memory_nx(unsigned long addr, int numpages);
int set_memory_ro(unsigned long addr, int numpages);
int set_memory_rw(unsigned long addr, int numpages);

void clflush_cache_range(void *addr, int size);

#ifdef CONFIG_DEBUG_RODATA
Expand Down

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