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x86/mm/cpa: Better use CLFLUSHOPT 

Currently we issue an MFENCE before and after flushing a range. This
means that if we flush a bunch of single page ranges -- like with the
cpa array, we issue a whole bunch of superfluous MFENCEs.

Reorgainze the code a little to avoid this.

[ mingo: capitalize instructions, tweak changelog and comments. ]

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rik van Riel <riel@surriel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tom.StDenis@amd.com
Cc: dave.hansen@intel.com
Link: http://lkml.kernel.org/r/20181203171043.626999883@infradead.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2018-12-03 18:03:52 +01:00 committed by Ingo Molnar
parent fe0937b24f
commit c38116bb94
1 changed files with 17 additions and 12 deletions
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29
arch/x86/mm/pageattr.c
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@ -251,15 +251,7 @@ static unsigned long __cpa_addr(struct cpa_data *cpa, unsigned long idx)
* Flushing functions
*/
/**
* clflush_cache_range - flush a cache range with clflush
* @vaddr: virtual start address
* @size: number of bytes to flush
*
* clflushopt is an unordered instruction which needs fencing with mfence or
* sfence to avoid ordering issues.
*/
void clflush_cache_range(void *vaddr, unsigned int size)
static void clflush_cache_range_opt(void *vaddr, unsigned int size)
{
const unsigned long clflush_size = boot_cpu_data.x86_clflush_size;
void *p = (void *)((unsigned long)vaddr & ~(clflush_size - 1));
@ -268,11 +260,22 @@ void clflush_cache_range(void *vaddr, unsigned int size)
if (p >= vend)
return;
mb();
for (; p < vend; p += clflush_size)
clflushopt(p);
}
/**
* clflush_cache_range - flush a cache range with clflush
* @vaddr: virtual start address
* @size: number of bytes to flush
*
* CLFLUSHOPT is an unordered instruction which needs fencing with MFENCE or
* SFENCE to avoid ordering issues.
*/
void clflush_cache_range(void *vaddr, unsigned int size)
{
mb();
clflush_cache_range_opt(vaddr, size);
mb();
}
EXPORT_SYMBOL_GPL(clflush_cache_range);
@ -333,6 +336,7 @@ static void cpa_flush(struct cpa_data *data, int cache)
if (!cache)
return;
mb();
for (i = 0; i < cpa->numpages; i++) {
unsigned long addr = __cpa_addr(cpa, i);
unsigned int level;
@ -343,8 +347,9 @@ static void cpa_flush(struct cpa_data *data, int cache)
* Only flush present addresses:
*/
if (pte && (pte_val(*pte) & _PAGE_PRESENT))
clflush_cache_range((void *)addr, PAGE_SIZE);
clflush_cache_range_opt((void *)addr, PAGE_SIZE);
}
mb();
}
static bool overlaps(unsigned long r1_start, unsigned long r1_end,