Re: [edk2-devel] [PATCH v2 2/2] UefiCpuPkg/CpuMpPei: Don't write CR3 in ConvertMemoryPageToNotPresent

["Laszlo Ersek" <lersek@redhat.com>]

On 1/17/24 07:22, Zhiguang Liu wrote:
> The purpose of writing CR3 in ConvertMemoryPageToNotPresent is just
> to flush TLB, because CR3 won't be changed in function
> ConvertMemoryPageToNotPresent.
> After ConvertMemoryPageToNotPresent, there is always a flush TLB
> function. Also, because ConvertMemoryPageToNotPresent in called in a
> loop, to improve performance, there is no need to flush TLB
> inside ConvertMemoryPageToNotPresent. Just flushing TLB after the loop
> is enough.
> 
> 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>
> Signed-off-by: Zhiguang Liu <zhiguang.liu@intel.com>
> ---
>  UefiCpuPkg/CpuMpPei/CpuPaging.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/UefiCpuPkg/CpuMpPei/CpuPaging.c b/UefiCpuPkg/CpuMpPei/CpuPaging.c
> index 15c7015fb8..b923d9b502 100644
> --- a/UefiCpuPkg/CpuMpPei/CpuPaging.c
> +++ b/UefiCpuPkg/CpuMpPei/CpuPaging.c
> @@ -76,7 +76,8 @@ AllocatePageTableMemory (
>  
>  /**
>    This function modifies the page attributes for the memory region specified
> -  by BaseAddress and Length to not present.
> +  by BaseAddress and Length to not present. This function only change page
> +  table, but not flush TLB. Caller have the responsbility to flush TLB.
>  
>    Caller should make sure BaseAddress and Length is at page boundary.
>  
> @@ -167,7 +168,6 @@ ConvertMemoryPageToNotPresent (
>    }
>  
>    ASSERT_EFI_ERROR (Status);
> -  AsmWriteCr3 (PageTable);
>    return Status;
>  }
>  

Reviewed-by: Laszlo Ersek <lersek@redhat.com>



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#113946): https://edk2.groups.io/g/devel/message/113946
Mute This Topic: https://groups.io/mt/103781133/7686176
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/leave/12367111/7686176/1913456212/xyzzy [rebecca@openfw.io]
-=-=-=-=-=-=-=-=-=-=-=-