This is a note to let you know that I've just added the patch titled
KVM: x86: Use guest MAXPHYADDR from CPUID.0x8000_0008 iff TDP is enabled
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-use-guest-maxphyaddr-from-cpuid.0x8000_0008-iff-tdp-is-enabled.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 4bf48e3c0aafd32b960d341c4925b48f416f14a5 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@xxxxxxxxxx>
Date: Wed, 23 Jun 2021 16:05:46 -0700
Subject: KVM: x86: Use guest MAXPHYADDR from CPUID.0x8000_0008 iff TDP is enabled
From: Sean Christopherson <seanjc@xxxxxxxxxx>
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@xxxxxxxxxxxxxxx
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Message-Id: <20210623230552.4027702-2-seanjc@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/x86/kvm/cpuid.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -633,8 +633,14 @@ static inline int __do_cpuid_ent(struct
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;
/*
Patches currently in stable-queue which might be from seanjc@xxxxxxxxxx are
queue-4.9/kvm-x86-use-guest-maxphyaddr-from-cpuid.0x8000_0008-iff-tdp-is-enabled.patch
