Re: [PATCH v4 6/6] OvmfPkg/QemuVideoDxe: Bypass NULL pointer detection during VBE SHIM installing

["Wang, Jian J" <jian.j.wang@intel.com>]

Got it. Thank you very much for the advice and information.

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Tuesday, October 10, 2017 4:13 PM
> To: Wang, Jian J <jian.j.wang@intel.com>; edk2-devel@lists.01.org
> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Wolman, Ayellet
> <ayellet.wolman@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>; Dong, Eric
> <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> Subject: Re: [edk2] [PATCH v4 6/6] OvmfPkg/QemuVideoDxe: Bypass NULL
> pointer detection during VBE SHIM installing
> 
> On 10/10/17 03:50, Wang, Jian J wrote:
> > I have summary in each patch email.
> 
> Sure, you have a commit message, but you didn't point out any v3->v4
> changes. (If there are no v3->v4 changes, then please pick up the R-b's
> received for v3.)
> 
> > I removed the CC of some patches because
> > there's no update from v3 to v4. I thought this could remind you of this
> situation.
> > What's the recommended way? Keep the CC as-was and just add summaries in
> > cover letter?
> 
> Maintainers should always be CC'd, even if there are no changes relative
> to the previous version.
> 
> Personally I prefer summarizing the changes in the cover letter, and
> also explaining the changes in more detail -- or pointing out the lack
> of any changes -- on each individual patch.
> 
> If you have a bit of time for reading, I recommend the following wiki
> article:
> 
> https://github.com/tianocore/tianocore.github.io/wiki/Laszlo's-unkempt-git-
> guide-for-edk2-contributors-and-maintainers
> 
> In it, I had written down most everything that I have in mind about the
> edk2 development process. The following steps pertain to the current
> discussion (i.e., picking up feedback tags, adding Maintainer CC's, and
> pointing out changes per patch):
> 
> https://github.com/tianocore/tianocore.github.io/wiki/Laszlo's-unkempt-git-
> guide-for-edk2-contributors-and-maintainers#contrib-18
> 
> https://github.com/tianocore/tianocore.github.io/wiki/Laszlo's-unkempt-git-
> guide-for-edk2-contributors-and-maintainers#contrib-28
> 
> https://github.com/tianocore/tianocore.github.io/wiki/Laszlo's-unkempt-git-
> guide-for-edk2-contributors-and-maintainers#contrib-30
> 
> Thanks,
> Laszlo
> 
> 
> >
> >> -----Original Message-----
> >> From: Laszlo Ersek [mailto:lersek@redhat.com]
> >> Sent: Monday, October 09, 2017 11:56 PM
> >> To: Wang, Jian J <jian.j.wang@intel.com>; edk2-devel@lists.01.org
> >> Cc: Kinney, Michael D <michael.d.kinney@intel.com>; Wolman, Ayellet
> >> <ayellet.wolman@intel.com>; Yao, Jiewen <jiewen.yao@intel.com>; Dong,
> Eric
> >> <eric.dong@intel.com>; Zeng, Star <star.zeng@intel.com>
> >> Subject: Re: [edk2] [PATCH v4 6/6] OvmfPkg/QemuVideoDxe: Bypass NULL
> >> pointer detection during VBE SHIM installing
> >>
> >> On 10/09/17 17:54, Laszlo Ersek wrote:
> >>> On 10/09/17 16:17, Jian J Wang wrote:
> >>>> QemuVideoDxe driver will link VBE SHIM into page 0. If NULL pointer
> >>>> detection is enabled, this driver will fail to load. NULL pointer detection
> >>>> bypassing code is added to prevent such problem during boot.
> >>>>
> >>>> Please note that Windows 7 will try to access VBE SHIM during boot if it's
> >>>> installed, and then cause boot failure. This can be fixed by setting BIT7
> >>>> of PcdNullPointerDetectionPropertyMask to disable NULL pointer
> detection
> >>>> after EndOfDxe. As far as we know, there's no other OSs has such issue.
> >>>>
> >>>> Cc: Star Zeng <star.zeng@intel.com>
> >>>> Cc: Eric Dong <eric.dong@intel.com>
> >>>> Cc: Jiewen Yao <jiewen.yao@intel.com>
> >>>> Cc: Michael Kinney <michael.d.kinney@intel.com>
> >>>> Cc: Ayellet Wolman <ayellet.wolman@intel.com>
> >>>> Suggested-by: Ayellet Wolman <ayellet.wolman@intel.com>
> >>>> Contributed-under: TianoCore Contribution Agreement 1.1
> >>>> Signed-off-by: Jian J Wang <jian.j.wang@intel.com>
> >>>> ---
> >>>>  OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf |  1 +
> >>>>  OvmfPkg/QemuVideoDxe/VbeShim.c        | 14 ++++++++++++++
> >>>>  2 files changed, 15 insertions(+)
> >>>>
> >>>> diff --git a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
> >> b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
> >>>> index 577e07b0a8..ff68c99e96 100644
> >>>> --- a/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
> >>>> +++ b/OvmfPkg/QemuVideoDxe/QemuVideoDxe.inf
> >>>> @@ -77,3 +77,4 @@
> >>>>  [Pcd]
> >>>>    gOptionRomPkgTokenSpaceGuid.PcdDriverSupportedEfiVersion
> >>>>    gUefiOvmfPkgTokenSpaceGuid.PcdOvmfHostBridgePciDevId
> >>>> +
> >> gEfiMdeModulePkgTokenSpaceGuid.PcdNullPointerDetectionPropertyMask
> >>>> diff --git a/OvmfPkg/QemuVideoDxe/VbeShim.c
> >> b/OvmfPkg/QemuVideoDxe/VbeShim.c
> >>>> index e45a08e887..8ba5522cde 100644
> >>>> --- a/OvmfPkg/QemuVideoDxe/VbeShim.c
> >>>> +++ b/OvmfPkg/QemuVideoDxe/VbeShim.c
> >>>> @@ -75,6 +75,20 @@ InstallVbeShim (
> >>>>    UINTN                Printed;
> >>>>    VBE_MODE_INFO        *VbeModeInfo;
> >>>>
> >>>> +  if ((PcdGet8 (PcdNullPointerDetectionPropertyMask) & (BIT0|BIT7)) ==
> BIT0)
> >> {
> >>>> +    DEBUG ((
> >>>> +      DEBUG_WARN,
> >>>> +      "%a: page 0 protected, not installing VBE shim\n",
> >>>> +      __FUNCTION__
> >>>> +      ));
> >>>> +    DEBUG ((
> >>>> +      DEBUG_WARN,
> >>>> +      "%a: page 0 protection prevents Windows 7 from booting anyway\n",
> >>>> +      __FUNCTION__
> >>>> +      ));
> >>>> +    return;
> >>>> +  }
> >>>> +
> >>>>    Segment0 = 0x00000;
> >>>>    SegmentC = 0xC0000;
> >>>>    SegmentF = 0xF0000;
> >>>>
> >>>
> >>> If this patch is entirely identical to the previous version (v3), then
> >>> you should have please picked up the review tags from Jordan and myself,
> >>> the ones that you got for v3:
> >>>
> >>> http://mid.mail-
> >> archive.com/150696711831.2454.16712170525103415248@jljusten-skl
> >>>
> >>> http://mid.mail-archive.com/d1a20be5-8dbf-8ce6-1738-
> >> d03b330047cc@redhat.com
> >>>
> >>> This way we can quickly filter out already reviewed patches, and avoid
> >>> re-reviewing when there are no changes.
> >>>
> >>>
> >>> Your cover letter v4 0/6 also does not summarize the changes relative to
> >>> v3; in the future please don't forget about that.
> >>
> >> ... personal CC's for OvmfPkg maintainers and reviewers are also missing
> >> from this patch. Please check "Maintainers.txt" every time.
> >>
> >> Thanks
> >> Laszlo