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target/i386/kvm: Fix disabling MPX on "-cpu host" with MPX-capable host

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Since KVM commit 5f76f6f5ff96 ("KVM: nVMX: Do not expose MPX VMX controls when guest MPX disabled")
it is not possible to disable MPX on a "-cpu host" just by adding "-mpx"
there if the host CPU does indeed support MPX.
QEMU will fail to set MSR_IA32_VMX_TRUE_{EXIT,ENTRY}_CTLS MSRs in this case
and so trigger an assertion failure.

Instead, besides "-mpx" one has to explicitly add also
"-vmx-exit-clear-bndcfgs" and "-vmx-entry-load-bndcfgs" to QEMU command
line to make it work, which is a bit convoluted.

Make the MPX-related bits in FEAT_VMX_{EXIT,ENTRY}_CTLS dependent on MPX
being actually enabled so such workarounds are no longer necessary.

Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Message-Id: <51aa2125c76363204cc23c27165e778097c33f0b.1653323077.git.maciej.szmigiero@oracle.com>
Cc: qemu-stable@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Maciej S. Szmigiero 2022-05-23 18:26:58 +02:00 • committed by Paolo Bonzini
parent dba2b2941c
commit 267b5e7e37
1 changed files with 8 additions and 0 deletions
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8
target/i386/cpu.c
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@ -1355,6 +1355,14 @@ static FeatureDep feature_dependencies[] = {
.from = { FEAT_7_0_EBX, CPUID_7_0_EBX_INVPCID },
.to = { FEAT_VMX_SECONDARY_CTLS, VMX_SECONDARY_EXEC_ENABLE_INVPCID },
},
{
.from = { FEAT_7_0_EBX, CPUID_7_0_EBX_MPX },
.to = { FEAT_VMX_EXIT_CTLS, VMX_VM_EXIT_CLEAR_BNDCFGS },
},
{
.from = { FEAT_7_0_EBX, CPUID_7_0_EBX_MPX },
.to = { FEAT_VMX_ENTRY_CTLS, VMX_VM_ENTRY_LOAD_BNDCFGS },
},
{
.from = { FEAT_7_0_EBX, CPUID_7_0_EBX_RDSEED },
.to = { FEAT_VMX_SECONDARY_CTLS, VMX_SECONDARY_EXEC_RDSEED_EXITING },