Re: [PATCH 0/2] OvmfPkg: check 64bit mmio window for resource conflicts

["Yao, Jiewen" <jiewen.yao@intel.com>]

I recommend also add detailed information in the code as comment.

That can help people who only reads the code directly.

Thank you
Yao, Jiewen

> -----Original Message-----
> From: Gerd Hoffmann <kraxel@redhat.com>
> Sent: Friday, January 6, 2023 11:32 PM
> To: Ard Biesheuvel <ardb@kernel.org>
> Cc: devel@edk2.groups.io; Ard Biesheuvel <ardb+tianocore@kernel.org>;
> László Érsek <lersek@redhat.com>; Justen, Jordan L
> <jordan.l.justen@intel.com>; Pawel Polawski <ppolawsk@redhat.com>;
> Oliver Steffen <osteffen@redhat.com>; Yao, Jiewen <jiewen.yao@intel.com>
> Subject: Re: [PATCH 0/2] OvmfPkg: check 64bit mmio window for resource
> conflicts
> 
> On Fri, Jan 06, 2023 at 03:14:53PM +0100, Ard Biesheuvel wrote:
> > Hi Gerd,
> >
> > On Fri, 6 Jan 2023 at 15:04, Gerd Hoffmann <kraxel@redhat.com> wrote:
> > >
> > >
> > >
> > > Gerd Hoffmann (2):
> > >   OvmfPkg/PlatformInitLib: update PlatformScanOrAdd64BitE820Ram
> > >     documentation
> > >   OvmfPkg/PlatformInitLib: check 64bit mmio window for resource
> > >     conflicts
> > >
> > >  OvmfPkg/Library/PlatformInitLib/MemDetect.c | 63
> +++++++++++++++++----
> > >  1 file changed, 51 insertions(+), 12 deletions(-)
> > >
> >
> > Mind adding a teeny bit of context to explain why this is needed? No
> > need to respin or anything - just want to make sure i understand the
> > problem and the solution.
> 
> qemu reserves some address space below 1TB when emulating amd
> processors
> because that is the address range used by the amd iommu.  This avoids
> placing the mmio window at a overlapping range.
> 
> https://bugzilla.tianocore.org/show_bug.cgi?id=4251
> 
> (guess I should add a link to the commit message ...)
> 
> take care,
>   Gerd