[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v3 10/12] x86/mm: make code robust to future PAT changes
It may be desirable to change Xen's PAT for various reasons. This requires changes to several _PAGE_* macros as well. Add static assertions to check that XEN_MSR_PAT is consistent with the _PAGE_* macros, and that _PAGE_WB is 0 as required by Linux. Signed-off-by: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx> --- xen/arch/x86/mm.c | 36 ++++++++++++++++++++++++++++++++++++ 1 file changed, 36 insertions(+) diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index a8def47aa3bf9770576c62a190032d45d63dd86e..7fb1a0f91910952640378f316a68096a08895b37 100644 --- a/xen/arch/x86/mm.c +++ b/xen/arch/x86/mm.c @@ -6357,8 +6357,44 @@ unsigned long get_upper_mfn_bound(void) static void __init __maybe_unused build_assertions(void) { + /* A bunch of static assertions to check that the XEN_MSR_PAT is valid + * and consistent with the _PAGE_* macros */ BUILD_BUG_ON(XEN_MSR_PAT != 0x050100070406ULL && "wrong XEN_MSR_PAT breaks PV guests"); + BUILD_BUG_ON(_PAGE_WB && "Linux requires _PAGE_WB to be 0"); +#define PAT_VALUE(v) (0xFF & (XEN_MSR_PAT >> (8 * (v)))) +#define BAD_VALUE(v) ((v) < 0 || (v) > 7 || \ + (v) == X86_MT_RESERVED_1 || (v) == X86_MT_RESERVED_2) +#define BAD_PAT_VALUE(v) BUILD_BUG_ON(BAD_VALUE(PAT_VALUE(v))) + BAD_PAT_VALUE(0); + BAD_PAT_VALUE(1); + BAD_PAT_VALUE(2); + BAD_PAT_VALUE(3); + BAD_PAT_VALUE(4); + BAD_PAT_VALUE(5); + BAD_PAT_VALUE(6); + BAD_PAT_VALUE(7); +#undef BAD_PAT_VALUE +#undef BAD_VALUE +#define PAT_SHIFT(page_value) (((page_value) & _PAGE_PAT) >> 5 | \ + ((page_value) & (_PAGE_PCD | _PAGE_PWT)) >> 3) +#define CHECK_PAGE_VALUE(page_value) do { \ + /* Check that the _PAGE_* macros only use bits from PAGE_CACHE_ATTRS */ \ + BUILD_BUG_ON(((_PAGE_##page_value) & PAGE_CACHE_ATTRS) != \ + (_PAGE_##page_value)); \ + /* Check that the _PAGE_* are consistent with XEN_MSR_PAT */ \ + BUILD_BUG_ON(PAT_VALUE(PAT_SHIFT(_PAGE_##page_value)) != \ + (X86_MT_##page_value)); \ +} while (0) + CHECK_PAGE_VALUE(WT); + CHECK_PAGE_VALUE(WB); + CHECK_PAGE_VALUE(WC); + CHECK_PAGE_VALUE(UC); + CHECK_PAGE_VALUE(UCM); + CHECK_PAGE_VALUE(WP); +#undef CHECK_PAGE_VALUE +#undef PAT_SHIFT +#undef PAT_VALUE } /* -- Sincerely, Demi Marie Obenour (she/her/hers) Invisible Things Lab
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