From b61b4fc490d7b41055e4f368af3152112aa25587 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Jun 2021 16:05:46 -0700 Subject: [PATCH] KVM: x86: Use guest MAXPHYADDR from CPUID.0x8000_0008 iff TDP is enabled BugLink: https://bugs.launchpad.net/bugs/1939440 commit 4bf48e3c0aafd32b960d341c4925b48f416f14a5 upstream. Ignore the guest MAXPHYADDR reported by CPUID.0x8000_0008 if TDP, i.e. NPT, is disabled, and instead use the host's MAXPHYADDR. Per AMD'S APM: Maximum guest physical address size in bits. This number applies only to guests using nested paging. When this field is zero, refer to the PhysAddrSize field for the maximum guest physical address size. Fixes: 24c82e576b78 ("KVM: Sanitize cpuid") Cc: stable@vger.kernel.org Signed-off-by: Sean Christopherson Message-Id: <20210623230552.4027702-2-seanjc@google.com> Signed-off-by: Paolo Bonzini Signed-off-by: Greg Kroah-Hartman Signed-off-by: Kamal Mostafa Signed-off-by: Kelsey Skunberg --- arch/x86/kvm/cpuid.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index 6fa946f983c9..6a8db8eb0e94 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -745,8 +745,14 @@ static inline int __do_cpuid_func(struct kvm_cpuid_entry2 *entry, u32 function, unsigned virt_as = max((entry->eax >> 8) & 0xff, 48U); unsigned phys_as = entry->eax & 0xff; - if (!g_phys_as) + /* + * Use bare metal's MAXPHADDR if the CPU doesn't report guest + * MAXPHYADDR separately, or if TDP (NPT) is disabled, as the + * guest version "applies only to guests using nested paging". + */ + if (!g_phys_as || !tdp_enabled) g_phys_as = phys_as; + entry->eax = g_phys_as | (virt_as << 8); entry->edx = 0; entry->ebx &= kvm_cpuid_8000_0008_ebx_x86_features; -- 2.39.5