Right now, ZONE_DEVICE memory is always set PG_reserved. We want to change that.
KVM has this weird use case that you can map anything from /dev/mem into the guest. pfn_valid() is not a reliable check whether the memmap was initialized and can be touched. pfn_to_online_page() makes sure that we have an initialized memmap (and don't have ZONE_DEVICE memory). Rewrite kvm_is_mmio_pfn() to make sure the function produces the same result once we stop setting ZONE_DEVICE pages PG_reserved. Cc: Paolo Bonzini <[email protected]> Cc: "Radim Krčmář" <[email protected]> Cc: Sean Christopherson <[email protected]> Cc: Vitaly Kuznetsov <[email protected]> Cc: Wanpeng Li <[email protected]> Cc: Jim Mattson <[email protected]> Cc: Joerg Roedel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: KarimAllah Ahmed <[email protected]> Cc: Michal Hocko <[email protected]> Cc: Dan Williams <[email protected]> Signed-off-by: David Hildenbrand <[email protected]> --- arch/x86/kvm/mmu.c | 29 +++++++++++++++++------------ 1 file changed, 17 insertions(+), 12 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 24c23c66b226..f03089a336de 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -2962,20 +2962,25 @@ static bool mmu_need_write_protect(struct kvm_vcpu *vcpu, gfn_t gfn, static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) { + struct page *page = pfn_to_online_page(pfn); + + /* + * ZONE_DEVICE pages are never online. Online pages that are reserved + * either indicate the zero page or MMIO pages. + */ + if (page) + return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)); + + /* + * Anything with a valid (but not online) memmap could be ZONE_DEVICE. + * Treat only UC/UC-/WC pages as MMIO. + */ if (pfn_valid(pfn)) - return !is_zero_pfn(pfn) && PageReserved(pfn_to_page(pfn)) && - /* - * Some reserved pages, such as those from NVDIMM - * DAX devices, are not for MMIO, and can be mapped - * with cached memory type for better performance. - * However, the above check misconceives those pages - * as MMIO, and results in KVM mapping them with UC - * memory type, which would hurt the performance. - * Therefore, we check the host memory type in addition - * and only treat UC/UC-/WC pages as MMIO. - */ - (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn)); + return !pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn); + /* + * Any RAM that has no memmap (e.g., mapped via /dev/mem) is not MMIO. + */ return !e820__mapped_raw_any(pfn_to_hpa(pfn), pfn_to_hpa(pfn + 1) - 1, E820_TYPE_RAM); -- 2.21.0 _______________________________________________ devel mailing list [email protected] http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
