The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From e30a7d623dccdb3f880fbcad980b0cb589a1da45 Mon Sep 17 00:00:00 2001

From: Sean Christopherson sean.j.christopherson@intel.com Date: Tue, 7 Jan 2020 16:12:10 -0800 Subject: [PATCH] KVM: x86/mmu: Apply max PA check for MMIO sptes to 32-bit KVM

Remove the bogus 64-bit only condition from the check that disables MMIO spte optimization when the system supports the max PA, i.e. doesn't have any reserved PA bits. 32-bit KVM always uses PAE paging for the shadow MMU, and per Intel's SDM:

PAE paging translates 32-bit linear addresses to 52-bit physical addresses.

The kernel's restrictions on max physical addresses are limits on how much memory the kernel can reasonably use, not what physical addresses are supported by hardware.

Fixes: ce88decffd17 ("KVM: MMU: mmio page fault support") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson sean.j.christopherson@intel.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 2992ff7b42a7..57e4dbddba72 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -6193,7 +6193,7 @@ static void kvm_set_mmio_spte_mask(void) * If reserved bit is not supported, clear the present bit to disable * mmio page fault. */ - if (IS_ENABLED(CONFIG_X86_64) && shadow_phys_bits == 52) + if (shadow_phys_bits == 52) mask &= ~1ull;

kvm_mmu_set_mmio_spte_mask(mask, mask, ACC_WRITE_MASK | ACC_USER_MASK);