Re: [edk2-devel] [PATCH V1 1/1] UefiCpuPkg/ResetVector: Cache Disable should not be set by default in CR0

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

The patch resolves an issue in Boot Guard enabled system that NEM is already enabled by Boot Guard, disabling cache evicts all cache content which is unexpected.

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

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Ni, Ray
> Sent: Wednesday, July 26, 2023 5:56 PM
> To: Xue, Shengfeng <xueshengfeng@byosoft.com.cn>; devel@edk2.groups.io;
> Dong, Eric <eric.dong@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>;
> kraxel@redhat.com; De, Debkumar <debkumar.de@intel.com>; West, Catharine
> <catharine.west@intel.com>
> Cc: Wu, MingliangX <mingliangx.wu@intel.com>
> Subject: Re: [edk2-devel] [PATCH V1 1/1] UefiCpuPkg/ResetVector: Cache
> Disable should not be set by default in CR0
> 
> This patch is not right.
> 
> Intel SDM explicitly says the initial CR0 value is 6000_0010. CD bit is set.
> 
> So the ResetVector code that still sets CD bit should be good.
> 
> If you are facing NEM enable failure, can you change your NEM enable logic to
> explicitly clear CD bit instead of changing here?
> 
> Thanks,
> Ray
> 
> 
> > -----Original Message-----
> > From: xueshengfeng <xueshengfeng@byosoft.com.cn>
> > Sent: Wednesday, July 26, 2023 5:48 PM
> > To: devel@edk2.groups.io; Dong, Eric <eric.dong@intel.com>; Ni, Ray
> > <ray.ni@intel.com>; Kumar, Rahul R <rahul.r.kumar@intel.com>;
> > kraxel@redhat.com; De, Debkumar <debkumar.de@intel.com>; West, Catharine
> > <catharine.west@intel.com>
> > Cc: Wu, MingliangX <mingliangx.wu@intel.com>; Wu
> > Subject: [PATCH V1 1/1] UefiCpuPkg/ResetVector: Cache Disable should not be
> > set by default in CR0
> >
> > From: "Wu, MingliangX" <mingliangx.wu@intel.com>
> >
> > REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4511
> >
> > With 64 bit build we are seeing the CD in control register CR 0 set.
> > This causes the NEM to disabled for some specific bios profiles.
> >
> > Cc: Eric Dong <eric.dong@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Rahul Kumar <rahul1.kumar@intel.com>
> > Cc: Gerd Hoffmann <kraxel@redhat.com>
> > Cc: Debkumar De <debkumar.de@intel.com>
> > Cc: Catharine West <catharine.west@intel.com>
> > Signed-off-by: Wu, Mingliang <mingliangx.wu@intel.com>
> > ---
> >  UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm
> > b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm
> > index f59fc6ead4ba..4af2e875c31c 100644
> > --- a/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm
> > +++ b/UefiCpuPkg/ResetVector/Vtf0/Ia16/Real16ToFlat32.asm
> > @@ -7,7 +7,7 @@
> >  ;
> >  ;------------------------------------------------------------------------------
> >
> > -%define SEC_DEFAULT_CR0  0x40000023
> > +%define SEC_DEFAULT_CR0  0x00000023
> >  %define SEC_DEFAULT_CR4  0x640
> >
> >  BITS    16
> > --
> > 2.26.2.windows.1
> >
> 
> 
> 
> 
> 



-=-=-=-=-=-=-=-=-=-=-=-
Groups.io Links: You receive all messages sent to this group.
View/Reply Online (#107527): https://edk2.groups.io/g/devel/message/107527
Mute This Topic: https://groups.io/mt/100367559/7686176
Group Owner: devel+owner@edk2.groups.io
Unsubscribe: https://edk2.groups.io/g/devel/leave/12367111/7686176/1913456212/xyzzy [rebecca@openfw.io]
-=-=-=-=-=-=-=-=-=-=-=-