[Xen-devel] [PATCH v7 4/7] VMX: Disable SMAP feature when guest is in non-paging mode

[Feng Wu <feng.wu@xxxxxxxxx>]

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@xxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
---
 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 00cab8a..b6c022b 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -1320,12 +1320,12 @@ 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


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