* [PATCH v2 4/7] VMX: Disable SMAP feature when guest is in non-paging mode
@ 2014-04-23 14:36 Feng Wu
2014-04-23 10:35 ` Andrew Cooper
0 siblings, 1 reply; 2+ messages in thread
From: Feng Wu @ 2014-04-23 14:36 UTC (permalink / raw)
To: xen-devel
Cc: kevin.tian, Feng Wu, JBeulich, andrew.cooper3, eddie.dong,
jun.nakajima, ian.campbell
SMAP is disabled if CPU is in non-paging mode in hardware.
However Xen always uses paging mode to emulate guest non-paging
mode with HAP. To emulate this behavior, SMAP needs to be manually
disabled when guest switches to non-paging mode.
This logic is similiar with SMEP.
Signed-off-by: Feng Wu <feng.wu@intel.com>
---
xen/arch/x86/hvm/vmx/vmx.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index 94f3db2..79dd272 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1310,12 +1310,12 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned int cr)
if ( !hvm_paging_enabled(v) )
{
/*
- * SMEP is disabled if CPU is in non-paging mode in hardware.
+ * SMEP/SMAP is disabled if CPU is in non-paging mode in hardware.
* However Xen always uses paging mode to emulate guest non-paging
- * mode. To emulate this behavior, SMEP needs to be manually
+ * mode. To emulate this behavior, SMEP/SMAP needs to be manually
* disabled when guest VCPU is in non-paging mode.
*/
- v->arch.hvm_vcpu.hw_cr[4] &= ~X86_CR4_SMEP;
+ v->arch.hvm_vcpu.hw_cr[4] &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
}
__vmwrite(GUEST_CR4, v->arch.hvm_vcpu.hw_cr[4]);
break;
--
1.8.3.1
^ permalink raw reply related [flat|nested] 2+ messages in thread* Re: [PATCH v2 4/7] VMX: Disable SMAP feature when guest is in non-paging mode
2014-04-23 14:36 [PATCH v2 4/7] VMX: Disable SMAP feature when guest is in non-paging mode Feng Wu
@ 2014-04-23 10:35 ` Andrew Cooper
0 siblings, 0 replies; 2+ messages in thread
From: Andrew Cooper @ 2014-04-23 10:35 UTC (permalink / raw)
To: Feng Wu
Cc: kevin.tian, ian.campbell, eddie.dong, xen-devel, JBeulich,
jun.nakajima
On 23/04/14 15:36, Feng Wu wrote:
> SMAP is disabled if CPU is in non-paging mode in hardware.
> However Xen always uses paging mode to emulate guest non-paging
> mode with HAP. To emulate this behavior, SMAP needs to be manually
> disabled when guest switches to non-paging mode.
>
> This logic is similiar with SMEP.
>
> Signed-off-by: Feng Wu <feng.wu@intel.com>
Reviewed-by: Andrew Cooper<andrew.cooper3@citrix.com>
> ---
> xen/arch/x86/hvm/vmx/vmx.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 94f3db2..79dd272 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1310,12 +1310,12 @@ static void vmx_update_guest_cr(struct vcpu *v, unsigned int cr)
> if ( !hvm_paging_enabled(v) )
> {
> /*
> - * SMEP is disabled if CPU is in non-paging mode in hardware.
> + * SMEP/SMAP is disabled if CPU is in non-paging mode in hardware.
> * However Xen always uses paging mode to emulate guest non-paging
> - * mode. To emulate this behavior, SMEP needs to be manually
> + * mode. To emulate this behavior, SMEP/SMAP needs to be manually
> * disabled when guest VCPU is in non-paging mode.
> */
> - v->arch.hvm_vcpu.hw_cr[4] &= ~X86_CR4_SMEP;
> + v->arch.hvm_vcpu.hw_cr[4] &= ~(X86_CR4_SMEP | X86_CR4_SMAP);
> }
> __vmwrite(GUEST_CR4, v->arch.hvm_vcpu.hw_cr[4]);
> break;
^ permalink raw reply [flat|nested] 2+ messages in thread
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