Re: [edk2-devel] [PATCH] UefiCpuPkg: add volatile qualifier to page table related variable

["Ni, Ray" <ray.ni@intel.com>]

Reviewed-by: Ray Ni <ray.ni@intel.com>

Thanks,
Ray
> -----Original Message-----
> From: Zhou, Jianfeng <jianfeng.zhou@intel.com>
> Sent: Wednesday, February 21, 2024 9:25 AM
> To: devel@edk2.groups.io
> Cc: Zhou, Jianfeng <jianfeng.zhou@intel.com>; Ni, Ray <ray.ni@intel.com>;
> Laszlo Ersek <lersek@redhat.com>; Kumar, Rahul R
> <rahul.r.kumar@intel.com>; Gerd Hoffmann <kraxel@redhat.com>
> Subject: [PATCH] UefiCpuPkg: add volatile qualifier to page table related
> variable
> 
> Add volatile qualifier to page table related variable to prevent
> compiler from optimizing away the variables which may lead to
> unexpected result.
> 
> Signed-off-by: Zhou Jianfeng <jianfeng.zhou@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Rahul Kumar <rahul1.kumar@intel.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> ---
>  UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c | 12
> ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> index 2ea40666cc..5cf6e8fea0 100644
> --- a/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> +++ b/UefiCpuPkg/Library/CpuPageTableLib/CpuPageTableMap.c
> @@ -26,7 +26,7 @@ PageTableLibSetPte4K (
>    IN IA32_MAP_ATTRIBUTE      *Mask
> 
>    )
> 
>  {
> 
> -  IA32_PTE_4K  LocalPte4K;
> 
> +  volatile IA32_PTE_4K  LocalPte4K;
> 
> 
> 
>    LocalPte4K.Uint64 = Pte4K->Uint64;
> 
>    if (Mask->Bits.PageTableBaseAddressLow ||
> Mask->Bits.PageTableBaseAddressHigh) {
> 
> @@ -78,7 +78,7 @@ PageTableLibSetPte4K (
>    }
> 
> 
> 
>    if (Pte4K->Uint64 != LocalPte4K.Uint64) {
> 
> -    Pte4K->Uint64 = LocalPte4K.Uint64;
> 
> +    *(volatile UINT64 *)&(Pte4K->Uint64) = LocalPte4K.Uint64;
> 
>    }
> 
>  }
> 
> 
> 
> @@ -100,7 +100,7 @@ PageTableLibSetPleB (
>    IN IA32_MAP_ATTRIBUTE                     *Mask
> 
>    )
> 
>  {
> 
> -  IA32_PAGE_LEAF_ENTRY_BIG_PAGESIZE  LocalPleB;
> 
> +  volatile IA32_PAGE_LEAF_ENTRY_BIG_PAGESIZE  LocalPleB;
> 
> 
> 
>    LocalPleB.Uint64 = PleB->Uint64;
> 
>    if (Mask->Bits.PageTableBaseAddressLow ||
> Mask->Bits.PageTableBaseAddressHigh) {
> 
> @@ -154,7 +154,7 @@ PageTableLibSetPleB (
>    }
> 
> 
> 
>    if (PleB->Uint64 != LocalPleB.Uint64) {
> 
> -    PleB->Uint64 = LocalPleB.Uint64;
> 
> +    *(volatile UINT64 *)&(PleB->Uint64) = LocalPleB.Uint64;
> 
>    }
> 
>  }
> 
> 
> 
> @@ -200,7 +200,7 @@ PageTableLibSetPnle (
>    IN IA32_MAP_ATTRIBUTE            *Mask
> 
>    )
> 
>  {
> 
> -  IA32_PAGE_NON_LEAF_ENTRY  LocalPnle;
> 
> +  volatile IA32_PAGE_NON_LEAF_ENTRY  LocalPnle;
> 
> 
> 
>    LocalPnle.Uint64 = Pnle->Uint64;
> 
>    if (Mask->Bits.Present) {
> 
> @@ -231,7 +231,7 @@ PageTableLibSetPnle (
>    LocalPnle.Bits.WriteThrough  = 0;
> 
>    LocalPnle.Bits.CacheDisabled = 0;
> 
>    if (Pnle->Uint64 != LocalPnle.Uint64) {
> 
> -    Pnle->Uint64 = LocalPnle.Uint64;
> 
> +    *(volatile UINT64 *)&(Pnle->Uint64) = LocalPnle.Uint64;
> 
>    }
> 
>  }
> 
> 
> 
> --
> 2.31.1.windows.1



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