* [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value
@ 2020-01-24 23:07 Sean Christopherson
2020-01-24 23:44 ` Randy Dunlap
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Sean Christopherson @ 2020-01-24 23:07 UTC (permalink / raw)
To: Paolo Bonzini
Cc: Sean Christopherson, Vitaly Kuznetsov, Wanpeng Li, Jim Mattson,
Joerg Roedel, kvm, linux-kernel, Krish Sadhukhan, Randy Dunlap
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);
--
2.24.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value
2020-01-24 23:07 [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value Sean Christopherson
@ 2020-01-24 23:44 ` Randy Dunlap
2020-01-25 9:32 ` Paolo Bonzini
2020-01-26 7:49 ` Krish Sadhukhan
2 siblings, 0 replies; 4+ messages in thread
From: Randy Dunlap @ 2020-01-24 23:44 UTC (permalink / raw)
To: Sean Christopherson, Paolo Bonzini
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel, Krish Sadhukhan
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);
>
--
~Randy
Reported-by: Randy Dunlap <rdunlap@infradead.org>
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value
2020-01-24 23:07 [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value Sean Christopherson
2020-01-24 23:44 ` Randy Dunlap
@ 2020-01-25 9:32 ` Paolo Bonzini
2020-01-26 7:49 ` Krish Sadhukhan
2 siblings, 0 replies; 4+ messages in thread
From: Paolo Bonzini @ 2020-01-25 9:32 UTC (permalink / raw)
To: Sean Christopherson
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel, Krish Sadhukhan, Randy Dunlap
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
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value
2020-01-24 23:07 [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value Sean Christopherson
2020-01-24 23:44 ` Randy Dunlap
2020-01-25 9:32 ` Paolo Bonzini
@ 2020-01-26 7:49 ` Krish Sadhukhan
2 siblings, 0 replies; 4+ messages in thread
From: Krish Sadhukhan @ 2020-01-26 7:49 UTC (permalink / raw)
To: Sean Christopherson, Paolo Bonzini
Cc: Vitaly Kuznetsov, Wanpeng Li, Jim Mattson, Joerg Roedel, kvm,
linux-kernel, Randy Dunlap
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>
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2020-01-26 7:51 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2020-01-24 23:07 [PATCH] KVM: x86: Take a u64 when checking for a valid dr7 value Sean Christopherson
2020-01-24 23:44 ` Randy Dunlap
2020-01-25 9:32 ` Paolo Bonzini
2020-01-26 7:49 ` Krish Sadhukhan
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