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| author | Oliver Upton <oupton@google.com> | 2020-08-18 17:24:28 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2020-10-21 23:36:32 +0200 |
| commit | 66570e966dd9cb4fd57811d0056c6472a14a2c41 (patch) | |
| tree | 06172486c1b55c545ea71bc0cd23c288c7b19fd1 /arch/x86/kvm/cpuid.h | |
| parent | kvm: x86: set wall_clock in kvm_write_wall_clock() (diff) | |
| download | linux-66570e966dd9cb4fd57811d0056c6472a14a2c41.tar.xz linux-66570e966dd9cb4fd57811d0056c6472a14a2c41.zip | |
kvm: x86: only provide PV features if enabled in guest's CPUID
KVM unconditionally provides PV features to the guest, regardless of the
configured CPUID. An unwitting guest that doesn't check
KVM_CPUID_FEATURES before use could access paravirt features that
userspace did not intend to provide. Fix this by checking the guest's
CPUID before performing any paravirtual operations.
Introduce a capability, KVM_CAP_ENFORCE_PV_FEATURE_CPUID, to gate the
aforementioned enforcement. Migrating a VM from a host w/o this patch to
a host with this patch could silently change the ABI exposed to the
guest, warranting that we default to the old behavior and opt-in for
the new one.
Reviewed-by: Jim Mattson <jmattson@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Change-Id: I202a0926f65035b872bfe8ad15307c026de59a98
Message-Id: <20200818152429.1923996-4-oupton@google.com>
Reviewed-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'arch/x86/kvm/cpuid.h')
| -rw-r--r-- | arch/x86/kvm/cpuid.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h index 1d2c4f2e4bb6..bf8577947ed2 100644 --- a/arch/x86/kvm/cpuid.h +++ b/arch/x86/kvm/cpuid.h @@ -5,6 +5,7 @@ #include "x86.h" #include <asm/cpu.h> #include <asm/processor.h> +#include <uapi/asm/kvm_para.h> extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly; void kvm_set_cpu_caps(void); @@ -313,4 +314,13 @@ static inline bool page_address_valid(struct kvm_vcpu *vcpu, gpa_t gpa) return PAGE_ALIGNED(gpa) && !(gpa >> cpuid_maxphyaddr(vcpu)); } +static __always_inline bool guest_pv_has(struct kvm_vcpu *vcpu, + unsigned int kvm_feature) +{ + if (!vcpu->arch.pv_cpuid.enforce) + return true; + + return vcpu->arch.pv_cpuid.features & (1u << kvm_feature); +} + #endif |