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 7adacf5eb2d2048045d9fd8fdab861fd9e7e2e96 Mon Sep 17 00:00:00 2001

From: Paolo Bonzini pbonzini@redhat.com Date: Wed, 4 Dec 2019 15:50:27 +0100 Subject: [PATCH] KVM: x86: use CPUID to locate host page table reserved bits

The comment in kvm_get_shadow_phys_bits refers to MKTME, but the same is actually true of SME and SEV. Just use CPUID[0x8000_0008].EAX[7:0] unconditionally if available, it is simplest and works even if memory is not encrypted.

Cc: stable@vger.kernel.org Reported-by: Tom Lendacky thomas.lendacky@amd.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 6f92b40d798c..1e4ee4f8de5f 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -538,16 +538,20 @@ EXPORT_SYMBOL_GPL(kvm_mmu_set_mask_ptes); static u8 kvm_get_shadow_phys_bits(void) { /* - * boot_cpu_data.x86_phys_bits is reduced when MKTME is detected - * in CPU detection code, but MKTME treats those reduced bits as - * 'keyID' thus they are not reserved bits. Therefore for MKTME - * we should still return physical address bits reported by CPUID. + * boot_cpu_data.x86_phys_bits is reduced when MKTME or SME are detected + * in CPU detection code, but the processor treats those reduced bits as + * 'keyID' thus they are not reserved bits. Therefore KVM needs to look at + * the physical address bits reported by CPUID. */ - if (!boot_cpu_has(X86_FEATURE_TME) || - WARN_ON_ONCE(boot_cpu_data.extended_cpuid_level < 0x80000008)) - return boot_cpu_data.x86_phys_bits; + if (likely(boot_cpu_data.extended_cpuid_level >= 0x80000008)) + return cpuid_eax(0x80000008) & 0xff;

- return cpuid_eax(0x80000008) & 0xff; + /* + * Quite weird to have VMX or SVM but not MAXPHYADDR; probably a VM with + * custom CPUID. Proceed with whatever the kernel found since these features + * aren't virtualizable (SME/SEV also require CPUIDs higher than 0x80000008). + */ + return boot_cpu_data.x86_phys_bits; }

static void kvm_mmu_reset_all_pte_masks(void)