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KVM: x86: Take a u64 when checking for a valid dr7 value

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Take a u64 instead of an unsigned long in kvm_dr7_valid() to fix a build
warning on i386 due to right-shifting a 32-bit value by 32 when checking
for bits being set in dr7[63:32].

Alternatively, the warning could be resolved by rewriting the check to
use an i386-friendly method, but taking a u64 fixes another oddity on
32-bit KVM.  Beause KVM implements natural width VMCS fields as u64s to
avoid layout issues between 32-bit and 64-bit, a devious guest can stuff
vmcs12->guest_dr7 with a 64-bit value even when both the guest and host
are 32-bit kernels.  KVM eventually drops vmcs12->guest_dr7[63:32] when
propagating vmcs12->guest_dr7 to vmcs02, but ideally KVM would not rely
on that behavior for correctness.

Cc: Jim Mattson <jmattson@google.com>
Cc: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Fixes: ecb697d10f70 ("KVM: nVMX: Check GUEST_DR7 on vmentry of nested guests")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2020-01-24 15:07:22 -08:00 committed by Paolo Bonzini
parent 8171cd6880
commit 9b5e85320f
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/x86.h
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@ -357,7 +357,7 @@ static inline bool kvm_pat_valid(u64 data)
return (data | ((data & 0x0202020202020202ull) << 1)) == data;
}
static inline bool kvm_dr7_valid(unsigned long data)
static inline bool kvm_dr7_valid(u64 data)
{
/* Bits [63:32] are reserved */
return !(data >> 32);