Hey I posted my comment on Bugzilla https://bugzilla.tianocore.org/show_bug.cgi?id=3987 Let's achieve EDKII/UEFI related discussion there. Thank you Yao, Jiewen > -----Original Message----- > From: Dionna Amalie Glaze <dionnaglaze@xxxxxxxxxx> > Sent: Tuesday, July 19, 2022 7:32 AM > To: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> > Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>; Peter Gonda <pgonda@xxxxxxxxxx>; > Borislav Petkov <bp@xxxxxxxxx>; Lutomirski, Andy <luto@xxxxxxxxxx>; > Christopherson,, Sean <seanjc@xxxxxxxxxx>; Andrew Morton <akpm@linux- > foundation.org>; Rodel, Jorg <jroedel@xxxxxxx>; Andi Kleen > <ak@xxxxxxxxxxxxxxx>; Kuppuswamy Sathyanarayanan > <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>; David Rientjes > <rientjes@xxxxxxxxxx>; Vlastimil Babka <vbabka@xxxxxxx>; Tom Lendacky > <thomas.lendacky@xxxxxxx>; Thomas Gleixner <tglx@xxxxxxxxxxxxx>; Peter > Zijlstra <peterz@xxxxxxxxxxxxx>; Paolo Bonzini <pbonzini@xxxxxxxxxx>; Ingo > Molnar <mingo@xxxxxxxxxx>; Varad Gautam <varad.gautam@xxxxxxxx>; > Dario Faggioli <dfaggioli@xxxxxxxx>; Hansen, Dave <dave.hansen@xxxxxxxxx>; > Mike Rapoport <rppt@xxxxxxxxxx>; David Hildenbrand <david@xxxxxxxxxx>; > Marcelo Cerri <marcelo.cerri@xxxxxxxxxxxxx>; tim.gardner@xxxxxxxxxxxxx; > Khalid ElMously <khalid.elmously@xxxxxxxxxxxxx>; Cox, Philip > <philip.cox@xxxxxxxxxxxxx>; the arch/x86 maintainers <x86@xxxxxxxxxx>; > Linux Memory Management List <linux-mm@xxxxxxxxx>; linux- > coco@xxxxxxxxxxxxxxx; linux-efi <linux-efi@xxxxxxxxxxxxxxx>; LKML <linux- > kernel@xxxxxxxxxxxxxxx>; Yao, Jiewen <jiewen.yao@xxxxxxxxx> > Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted > memory > > > I've talked with our firmware expert today and I think we have a problem > > with the approach when kernel declaries support of unaccepted memory. > > > > Is this Jiewen Yao? I've been trying to design the UEFI spec change > with him. The bootloader problem he commented with this morning was > something I wasn't fully considering. > > > This apporach doesn't work if we include bootloader into the picture: if > > EBS() called by bootloader we still cannot know if target kernel supports > > unaccepted memory and we return to the square 1. > > > > I think we should make it obvious from a kernel image if it supports > > unaccepted memory (with UTS_VERSION or other way). > > > > Any comments? > > Is this binary parsing trick already used in EDK2? If not, I wouldn't > want to introduce an ABI-solidifying requirement like that. > > A bit more cumbersome, but more flexible way to enable the feature is > an idea I had in a meeting today: > Make unaccepted memory support a feature-enabling EFI driver installed > to the EFI system partition. > > * The first time you boot (setup mode), you install an EFI driver that > just sets a feature Pcd to true (using a custom protocol as Ard had > suggested above). > * The second time you boot, if the feature Pcd is true, then the UEFI > is free to not accept memory and use the unaccepted memory type. The > bootloader will run after unaccepted memory has been allowed already, > so there is no accept-all event. > > The default behavior will be to accept all memory when GetMemoryMap is > called unless the feature pcd is set to true. > > We can then say this driver isn't needed once some new generation of > this technology comes along and we can require unaccepted memory > support as part of that technology's baseline, or we manage to update > the UEFI spec to have GetMemoryMapEx which has unaccepted memory > support baked in and the bootloaders all know to use it. > > The cloud experience will be, "is boot slow? Install this EFI driver > from the cloud service provider" to tell the UEFI to enable unaccepted > memory. > > -- > -Dionna Glaze, PhD (she/her)
