linux-kernel - Re: [PATCHv5 06/12] x86/boot/compressed: Handle unaccepted memory

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Date:   Tue, 31 May 2022 15:40:14 -0700
From:   Dionna Amalie Glaze <dionnaglaze@...gle.com>
To:     "Xu, Min M" <min.m.xu@...el.com>
Cc:     "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>,
        "Gao, Jiaqi" <jiaqi.gao@...el.com>,
        Michael Roth <michael.roth@....com>,
        Borislav Petkov <bp@...en8.de>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "Lutomirski, Andy" <luto@...nel.org>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Rodel, Jorg" <jroedel@...e.de>, Ard Biesheuvel <ardb@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Tom Lendacky <thomas.lendacky@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Ingo Molnar <mingo@...hat.com>,
        Varad Gautam <varad.gautam@...e.com>,
        Dario Faggioli <dfaggioli@...e.com>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        Mike Rapoport <rppt@...nel.org>,
        David Hildenbrand <david@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv5 06/12] x86/boot/compressed: Handle unaccepted memory

Hi y'all, I've made minimal changes to OVMF to prevalidate only up to
4GB and leave the rest unaccepted, as Thomas Lendacky recommended
https://github.com/AMDESE/ovmf/pull/4#issuecomment-1138606275 and ran
a memtouch test to see if this change behaves as expected. One thing
that struck me is that an 8GB machine reports 2044MB free with this
change (free -k) whereas without it, I see 7089MB free. I think that
unaccepted memory should be classified as free in meminfo, no? I'm not
familiar enough with that code to say what specific change needs to be
made.

(resent in text mode)


On Sun, May 15, 2022 at 11:47 PM Xu, Min M <min.m.xu@...el.com> wrote:
>
> On May 13, 2022 10:45 PM, Kirill A. Shutemov wrote:
> > On Fri, May 13, 2022 at 11:01:43AM +0200, Borislav Petkov wrote:
> > > + mroth
> > > - brijesh
> > >
> > > On Thu, May 12, 2022 at 10:34:02PM -0700, Dionna Amalie Glaze wrote:
> > > > Kirill, I've been tracking these changes to see if we can handle the
> > > > unaccepted memory type for SEV-SNP, but testing has been an issue.
> > > > The proposed patch in Ovmf to introduce unaccepted memory seems to
> > > > have stalled out last September
> > > > (https://www.mail-archive.com/devel@edk2.groups.io/msg35842.html)
> > > > and is particularly difficult to adapt to SEV-SNP since it doesn't
> > > > follow the TDVF way of initializing all memory. Is there a different
> > > > development I might have missed so that we might test these cases?
> > > > Without the UEFI introducing EFI_UNACCEPTED_MEMORY type, any
> > kernel
> > > > uses are essentially dead code.
> >
> > + Min, Jiaqi.
> >
> > I don't follow firmware development. Min, Jiaqi, could you comment?
> >
> We have prepared the patch for unaccepted memory and it is now working in our internal release.
> But there is an obstacle to upstream it to edk2 master branch.
> The patch-set depends on the definition of UEFI_RESOURCE_MEMORY_UNACCEPTED in PI spec. This is proposed in https://github.com/microsoft/mu_basecore/pull/66/files#diff-b20a11152d1ce9249c691be5690b4baf52069efadf2e2546cdd2eb663d80c9e4R237, according to UEFI-Code-First. The proposal was approved in 2021 in UEFI Mantis, and will be added to the new PI.next specification. (Till now it has not been added in the latest PI spec.)
> So UEFI_RESOURCE_MEMORY_UNACCEPTED cannot be added in MdePkg which make it difficult to submit the patch to edk2 community for review. See this link: https://edk2.groups.io/g/devel/message/87558
>
> Please be noted: UEFI_RESOURCE_MEMORY_UNACCEPTED (defined in PI spec) is different from EFI_UNACCEPTED_MEMORY (defined in UEFI spec)
>
> I will submit the patch-set once the new definition is added in the new PI.next spec.
>
> Thanks
> Min



-- 
-Dionna Glaze, PhD (she/her)