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

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

[Zhiguang Liu]

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;
 }
 
-- 
2.31.1.windows.1



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

[Laszlo Ersek]

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>



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

[Ni, Ray]

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

Thanks,
Ray
> -----Original Message-----
> From: Laszlo Ersek <lersek@redhat.com>
> Sent: Wednesday, January 17, 2024 6:24 PM
> To: devel@edk2.groups.io; Liu, Zhiguang <zhiguang.liu@intel.com>
> Cc: Ni, Ray <ray.ni@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>;
> Gerd Hoffmann <kraxel@redhat.com>
> Subject: Re: [edk2-devel] [PATCH v2 2/2] UefiCpuPkg/CpuMpPei: Don't write
> CR3 in ConvertMemoryPageToNotPresent
> 
> 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>



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