[Qemu-devel] [PATCH] target-i386: Don't forbid NX bit on PAE PDEs and PTEs

[Qemu-devel] [PATCH] target-i386: Don't forbid NX bit on PAE PDEs and PTEs

[William Grant]

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Commit e8f6d00c30ed88910d0d985f4b2bf41654172ceb ("target-i386: raise
page fault for reserved physical address bits") added a check that the
NX bit is not set on PAE PDPEs, but it also added it to rsvd_mask for
the rest of the function. This caused any PDEs or PTEs with NX set to be
erroneously rejected, making PAE guests with NX support unusable.

Signed-off-by: William Grant <wgrant@ubuntu.com>
---
 target-i386/helper.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/target-i386/helper.c b/target-i386/helper.c
index 47b982b..30cb0d0 100644
--- a/target-i386/helper.c
+++ b/target-i386/helper.c
@@ -615,8 +615,8 @@ int x86_cpu_handle_mmu_fault(CPUState *cs, vaddr addr,
             if (!(pdpe & PG_PRESENT_MASK)) {
                 goto do_fault;
             }
-            rsvd_mask |= PG_HI_USER_MASK | PG_NX_MASK;
-            if (pdpe & rsvd_mask) {
+            rsvd_mask |= PG_HI_USER_MASK;
+            if (pdpe & (rsvd_mask | PG_NX_MASK)) {
                 goto do_fault_rsvd;
             }
             ptep = PG_NX_MASK | PG_USER_MASK | PG_RW_MASK;
-- 
2.1.0


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Re: [Qemu-devel] [PATCH] target-i386: Don't forbid NX bit on PAE PDEs and PTEs

[Paolo Bonzini]

Il 24/08/2014 07:13, William Grant ha scritto:
> Commit e8f6d00c30ed88910d0d985f4b2bf41654172ceb ("target-i386: raise
> page fault for reserved physical address bits") added a check that the
> NX bit is not set on PAE PDPEs, but it also added it to rsvd_mask for
> the rest of the function. This caused any PDEs or PTEs with NX set to be
> erroneously rejected, making PAE guests with NX support unusable.
> 
> Signed-off-by: William Grant <wgrant@ubuntu.com>
> ---
>  target-i386/helper.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/target-i386/helper.c b/target-i386/helper.c
> index 47b982b..30cb0d0 100644
> --- a/target-i386/helper.c
> +++ b/target-i386/helper.c
> @@ -615,8 +615,8 @@ int x86_cpu_handle_mmu_fault(CPUState *cs, vaddr addr,
>              if (!(pdpe & PG_PRESENT_MASK)) {
>                  goto do_fault;
>              }
> -            rsvd_mask |= PG_HI_USER_MASK | PG_NX_MASK;
> -            if (pdpe & rsvd_mask) {
> +            rsvd_mask |= PG_HI_USER_MASK;
> +            if (pdpe & (rsvd_mask | PG_NX_MASK)) {
>                  goto do_fault_rsvd;
>              }
>              ptep = PG_NX_MASK | PG_USER_MASK | PG_RW_MASK;
> 

Thanks, applied to uq/master.

Paolo