| Message ID | 20200124230722.8964-1-sean.j.christopherson@intel.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Take a u64 when checking for a valid dr7 value | expand |
On 1/24/20 3:07 PM, Sean Christopherson wrote: > 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> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Thanks. > --- > arch/x86/kvm/x86.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 2d2ff855773b..3624665acee4 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -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); >
On 25/01/20 00:07, Sean Christopherson wrote: > 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> > --- > arch/x86/kvm/x86.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 2d2ff855773b..3624665acee4 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -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); > Queued, thanks. Paolo
On 1/24/20 3:07 PM, Sean Christopherson wrote: > 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> > --- > arch/x86/kvm/x86.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 2d2ff855773b..3624665acee4 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -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); Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 2d2ff855773b..3624665acee4 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -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);
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> --- arch/x86/kvm/x86.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)