On 05.11.19 02:37, Dan Williams wrote:
On Thu, Oct 24, 2019 at 5:10 AM David Hildenbrand <david@xxxxxxxxxx> wrote: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 <pbonzini@xxxxxxxxxx> Cc: "Radim Krčmář" <rkrcmar@xxxxxxxxxx> Cc: Sean Christopherson <sean.j.christopherson@xxxxxxxxx> Cc: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> Cc: Wanpeng Li <wanpengli@xxxxxxxxxxx> Cc: Jim Mattson <jmattson@xxxxxxxxxx> Cc: Joerg Roedel <joro@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: KarimAllah Ahmed <karahmed@xxxxxxxxx> Cc: Michal Hocko <mhocko@xxxxxxxxxx> Cc: Dan Williams <dan.j.williams@xxxxxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- 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.You might clarify that ZONE_DEVICE pages that belong to WB cacheable pmem have the correct memtype established by devm_memremap_pages().
/* * Anything with a valid (but not online) memmap could be ZONE_DEVICE. * Treat only UC/UC-/WC pages as MMIO. devm_memremap_pages() established * the correct memtype for WB cacheable ZONE_DEVICE pages. */ Thanks!
Other than that, feel free to add: Reviewed-by: Dan Williams <dan.j.williams@xxxxxxxxx>
-- Thanks, David / dhildenb
