From: Sean Christopherson <seanjc@google.com>
Date: Wed, 23 Jun 2021 16:05:47 -0700
Subject: KVM: x86: Use kernel's x86_phys_bits to handle reduced MAXPHYADDR
Git-commit: e39f00f60ebd2e7b295c37a05e6349df656d3eb8
Patch-mainline: v5.14-rc2
References: bsc#1114648
Use boot_cpu_data.x86_phys_bits instead of the raw CPUID information to
enumerate the MAXPHYADDR for KVM guests when TDP is disabled (the guest
version is only relevant to NPT/TDP).
When using shadow paging, any reductions to the host's MAXPHYADDR apply
to KVM and its guests as well, i.e. using the raw CPUID info will cause
KVM to misreport the number of PA bits available to the guest.
Unconditionally zero out the "Physical Address bit reduction" entry.
For !TDP, the adjustment is already done, and for TDP enumerating the
host's reduction is wrong as the reduction does not apply to GPAs.
Fixes: 9af9b94068fb ("x86/cpu/AMD: Handle SME reduction in physical address size")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210623230552.4027702-3-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
[ bp: Remove second hunk about 0x8000001F leaf as this kernel doesn't have it
and SLE12 is out of scope for SME anyway. ]
Acked-by: Borislav Petkov <bp@suse.de>
---
arch/x86/kvm/cpuid.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -652,8 +652,21 @@ 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)
+ /*
+ * If TDP (NPT) is disabled use the adjusted host MAXPHYADDR as
+ * the guest operates in the same PA space as the host, i.e.
+ * reductions in MAXPHYADDR for memory encryption affect shadow
+ * paging, too.
+ *
+ * If TDP is enabled but an explicit guest MAXPHYADDR is not
+ * provided, use the raw bare metal MAXPHYADDR as reductions to
+ * the HPAs do not affect GPAs.
+ */
+ if (!tdp_enabled)
+ g_phys_as = boot_cpu_data.x86_phys_bits;
+ else if (!g_phys_as)
g_phys_as = phys_as;
+
entry->eax = g_phys_as | (virt_as << 8);
entry->edx = 0;
/*