提交 627c2190 编写于 作者: T Thomas Gleixner 提交者: Shile Zhang

x86/mm/cpa: Avoid static protection checks on unmap

commit 69c31e69df3d2efc4ad7f53d500fdd920d3865a4 upstream.

If the new pgprot has the PRESENT bit cleared, then conflicts vs. RW/NX are
completely irrelevant.

Before:

 1G pages checked:                    2
 1G pages sameprot:                   0
 1G pages preserved:                  0
 2M pages checked:                  540
 2M pages sameprot:                 466
 2M pages preserved:                 47
 4K pages checked:               800770
 4K pages set-checked:             7668

After:

 1G pages checked:                    2
 1G pages sameprot:                   0
 1G pages preserved:                  0
 2M pages checked:                  540
 2M pages sameprot:                 466
 2M pages preserved:                 47
 4K pages checked:               800709
 4K pages set-checked:             7668
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Reviewed-by: NDave Hansen <dave.hansen@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Bin Yang <bin.yang@intel.com>
Cc: Mark Gross <mark.gross@intel.com>
Link: https://lkml.kernel.org/r/20180917143546.245849757@linutronix.deSigned-off-by: NShile Zhang <shile.zhang@linux.alibaba.com>
Acked-by: NJoseph Qi <joseph.qi@linux.alibaba.com>
上级 b4212f86
......@@ -526,6 +526,13 @@ static inline pgprot_t static_protections(pgprot_t prot, unsigned long start,
pgprotval_t forbidden, res;
unsigned long end;
/*
* There is no point in checking RW/NX conflicts when the requested
* mapping is setting the page !PRESENT.
*/
if (!(pgprot_val(prot) & _PAGE_PRESENT))
return prot;
/* Operate on the virtual address */
end = start + npg * PAGE_SIZE - 1;
......
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