From: Paolo Bonzini <pbonzini@redhat.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: jmattson@google.com,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: [PATCH] kvm: x86: Use KVM CPU capabilities to determine CR4 reserved bits
Date: Wed, 6 May 2020 05:44:36 -0400 [thread overview]
Message-ID: <20200506094436.3202-1-pbonzini@redhat.com> (raw)
Using CPUID data can be useful for the processor compatibility
check, but that's it. Using it to compute guest-reserved bits
can have both false positives (such as LA57 and UMIP which we
are already handling) and false negatives: in particular, with
this patch we don't allow anymore a KVM guest to set CR4.PKE
when CR4.PKE is clear on the host.
Fixes: b9dd21e104bc ("KVM: x86: simplify handling of PKRU")
Reported-by: Jim Mattson <jmattson@google.com>
Tested-by: Jim Mattson <jmattson@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/x86.c | 20 +++++---------------
1 file changed, 5 insertions(+), 15 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 45688d075044..e0639b2c332e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -929,19 +929,6 @@ EXPORT_SYMBOL_GPL(kvm_set_xcr);
__reserved_bits; \
})
-static u64 kvm_host_cr4_reserved_bits(struct cpuinfo_x86 *c)
-{
- u64 reserved_bits = __cr4_reserved_bits(cpu_has, c);
-
- if (kvm_cpu_cap_has(X86_FEATURE_LA57))
- reserved_bits &= ~X86_CR4_LA57;
-
- if (kvm_cpu_cap_has(X86_FEATURE_UMIP))
- reserved_bits &= ~X86_CR4_UMIP;
-
- return reserved_bits;
-}
-
static int kvm_valid_cr4(struct kvm_vcpu *vcpu, unsigned long cr4)
{
if (cr4 & cr4_reserved_bits)
@@ -9674,7 +9661,9 @@ int kvm_arch_hardware_setup(void *opaque)
if (!kvm_cpu_cap_has(X86_FEATURE_XSAVES))
supported_xss = 0;
- cr4_reserved_bits = kvm_host_cr4_reserved_bits(&boot_cpu_data);
+#define __kvm_cpu_cap_has(UNUSED_, f) kvm_cpu_cap_has(f)
+ cr4_reserved_bits = __cr4_reserved_bits(__kvm_cpu_cap_has, UNUSED_);
+#undef __kvm_cpu_cap_has
if (kvm_has_tsc_control) {
/*
@@ -9706,7 +9695,8 @@ int kvm_arch_check_processor_compat(void *opaque)
WARN_ON(!irqs_disabled());
- if (kvm_host_cr4_reserved_bits(c) != cr4_reserved_bits)
+ if (__cr4_reserved_bits(cpu_has, c) !=
+ __cr4_reserved_bits(cpu_has, &boot_cpu_data))
return -EIO;
return ops->check_processor_compatibility();
--
2.18.2
next reply other threads:[~2020-05-06 9:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-06 9:44 Paolo Bonzini [this message]
2020-05-18 4:52 ` [PATCH] kvm: x86: Use KVM CPU capabilities to determine CR4 reserved bits Xiaoyao Li
2020-05-18 12:31 ` Paolo Bonzini
2020-05-18 15:49 ` Xiaoyao Li
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