The patch below does not apply to the 4.19-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@xxxxxxxxxxxxxxx>.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
>From 7adacf5eb2d2048045d9fd8fdab861fd9e7e2e96 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Reported-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
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)
