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

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

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>



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#113985): https://edk2.groups.io/g/devel/message/113985
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]
-=-=-=-=-=-=-=-=-=-=-=-