Commit-ID: 69c31e69df3d2efc4ad7f53d500fdd920d3865a4 Gitweb: https://git.kernel.org/tip/69c31e69df3d2efc4ad7f53d500fdd920d3865a4 Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Mon, 17 Sep 2018 16:29:13 +0200 Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx> CommitDate: Thu, 27 Sep 2018 20:39:38 +0200 x86/mm/cpa: Avoid static protection checks on unmap 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: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Reviewed-by: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Bin Yang <bin.yang@xxxxxxxxx> Cc: Mark Gross <mark.gross@xxxxxxxxx> Link: https://lkml.kernel.org/r/20180917143546.245849757@xxxxxxxxxxxxx --- arch/x86/mm/pageattr.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/x86/mm/pageattr.c b/arch/x86/mm/pageattr.c index cdf52eb86f3a..8f9083eb21ac 100644 --- a/arch/x86/mm/pageattr.c +++ b/arch/x86/mm/pageattr.c @@ -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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