From: Peter Gonda <pgonda@google.com>
To: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Ard Biesheuvel <ardb@kernel.org>, Borislav Petkov <bp@alien8.de>,
Andy Lutomirski <luto@kernel.org>,
Sean Christopherson <seanjc@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Joerg Roedel <jroedel@suse.de>, Andi Kleen <ak@linux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
David Rientjes <rientjes@google.com>,
Vlastimil Babka <vbabka@suse.cz>,
Tom Lendacky <thomas.lendacky@amd.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Ingo Molnar <mingo@redhat.com>,
Varad Gautam <varad.gautam@suse.com>,
Dario Faggioli <dfaggioli@suse.com>,
Dave Hansen <dave.hansen@intel.com>,
Mike Rapoport <rppt@kernel.org>,
David Hildenbrand <david@redhat.com>,
Marcelo Cerri <marcelo.cerri@canonical.com>,
tim.gardner@canonical.com,
Khalid ElMously <khalid.elmously@canonical.com>,
philip.cox@canonical.com,
"the arch/x86 maintainers" <x86@kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
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linux-efi <linux-efi@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory
Date: Mon, 27 Jun 2022 10:17:30 -0600 [thread overview]
Message-ID: <CAMkAt6oJJaRM_dy=y2BP99VziPriVuA4jAmMc=G7njwJYKFgyg@mail.gmail.com> (raw)
In-Reply-To: <20220627122230.7eetepoufd5w3lxd@black.fi.intel.com>
On Mon, Jun 27, 2022 at 6:22 AM Kirill A. Shutemov
<kirill.shutemov@linux.intel.com> wrote:
>
> On Mon, Jun 27, 2022 at 01:54:45PM +0200, Ard Biesheuvel wrote:
> > On Mon, 27 Jun 2022 at 13:30, Kirill A. Shutemov
> > <kirill.shutemov@linux.intel.com> wrote:
> > >
> > > On Fri, Jun 24, 2022 at 10:37:10AM -0600, Peter Gonda wrote:
> > > > On Tue, Jun 14, 2022 at 6:03 AM Kirill A. Shutemov
> > > > <kirill.shutemov@linux.intel.com> wrote:
> > > > >
> > > > > UEFI Specification version 2.9 introduces the concept of memory
> > > > > acceptance: some Virtual Machine platforms, such as Intel TDX or AMD
> > > > > SEV-SNP, requiring memory to be accepted before it can be used by the
> > > > > guest. Accepting happens via a protocol specific for the Virtual
> > > > > Machine platform.
> > > > >
> > > > > Accepting memory is costly and it makes VMM allocate memory for the
> > > > > accepted guest physical address range. It's better to postpone memory
> > > > > acceptance until memory is needed. It lowers boot time and reduces
> > > > > memory overhead.
> > > > >
> > > > > The kernel needs to know what memory has been accepted. Firmware
> > > > > communicates this information via memory map: a new memory type --
> > > > > EFI_UNACCEPTED_MEMORY -- indicates such memory.
> > > > >
> > > > > Range-based tracking works fine for firmware, but it gets bulky for
> > > > > the kernel: e820 has to be modified on every page acceptance. It leads
> > > > > to table fragmentation, but there's a limited number of entries in the
> > > > > e820 table
> > > > >
> > > > > Another option is to mark such memory as usable in e820 and track if the
> > > > > range has been accepted in a bitmap. One bit in the bitmap represents
> > > > > 2MiB in the address space: one 4k page is enough to track 64GiB or
> > > > > physical address space.
> > > > >
> > > > > In the worst-case scenario -- a huge hole in the middle of the
> > > > > address space -- It needs 256MiB to handle 4PiB of the address
> > > > > space.
> > > > >
> > > > > Any unaccepted memory that is not aligned to 2M gets accepted upfront.
> > > > >
> > > > > The approach lowers boot time substantially. Boot to shell is ~2.5x
> > > > > faster for 4G TDX VM and ~4x faster for 64G.
> > > > >
> > > > > TDX-specific code isolated from the core of unaccepted memory support. It
> > > > > supposed to help to plug-in different implementation of unaccepted memory
> > > > > such as SEV-SNP.
> > > > >
> > > > > The tree can be found here:
> > > > >
> > > > > https://github.com/intel/tdx.git guest-unaccepted-memory
> > > >
> > > > Hi Kirill,
> > > >
> > > > I have a couple questions about this feature mainly about how cloud
> > > > customers can use this, I assume since this is a confidential compute
> > > > feature a large number of the users of these patches will be cloud
> > > > customers using TDX and SNP. One issue I see with these patches is how
> > > > do we as a cloud provider know whether a customer's linux image
> > > > supports this feature, if the image doesn't have these patches UEFI
> > > > needs to fully validate the memory, if the image does we can use this
> > > > new protocol. In GCE we supply our VMs with a version of the EDK2 FW
> > > > and the customer doesn't input into which UEFI we run, as far as I can
> > > > tell from the Azure SNP VM documentation it seems very similar. We
> > > > need to somehow tell our UEFI in the VM what to do based on the image.
> > > > The current way I can see to solve this issue would be to have our
> > > > customers give us metadata about their VM's image but this seems kinda
> > > > burdensome on our customers (I assume we'll have more features which
> > > > both UEFI and kernel need to both support inorder to be turned on like
> > > > this one) and error-prone, if a customer incorrectly labels their
> > > > image it may fail to boot.. Has there been any discussion about how to
> > > > solve this? My naive thoughts were what if UEFI and Kernel had some
> > > > sort of feature negotiation. Maybe that could happen via an extension
> > > > to exit boot services or a UEFI runtime driver, I'm not sure what's
> > > > best here just some ideas.
> > >
> > > Just as an idea, we can put info into UTS_VERSION which can be read from
> > > the built bzImage. We have info on SMP and preeption there already.
> > >
> >
> > Instead of hacking this into the binary, couldn't we define a protocol
> > that the kernel will call from the EFI stub (before EBS()) to identify
> > itself as an image that understands unaccepted memory, and knows how
> > to deal with it?
> >
> > That way, the firmware can accept all the memory on behalf of the OS
> > at ExitBootServices() time, unless the OS has indicated there is no
> > need to do so.
>
> I agree it would be better. But I think it would require change to EFI
> spec, no?
Could this somehow be amended on to the UEFI Specification version 2.9
change which added all of the unaccepted memory features?
>
> --
> Kirill A. Shutemov
next prev parent reply other threads:[~2022-06-27 16:17 UTC|newest]
Thread overview: 139+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-14 12:02 [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 01/14] x86/boot: Centralize __pa()/__va() definitions Kirill A. Shutemov
2022-06-23 17:37 ` Dave Hansen
2022-06-14 12:02 ` [PATCHv7 02/14] mm: Add support for unaccepted memory Kirill A. Shutemov
2022-06-14 12:57 ` Gupta, Pankaj
2022-06-17 19:28 ` Tom Lendacky
2022-06-17 20:53 ` Tom Lendacky
2022-07-21 15:14 ` Borislav Petkov
2022-07-21 15:49 ` Dave Hansen
2022-07-22 19:18 ` Borislav Petkov
2022-07-22 19:30 ` Dave Hansen
2022-07-25 12:23 ` Borislav Petkov
2022-07-25 12:38 ` David Hildenbrand
2022-07-25 12:53 ` Borislav Petkov
2022-07-26 14:30 ` David Hildenbrand
2022-07-25 13:00 ` Mike Rapoport
2022-07-25 13:05 ` Borislav Petkov
2022-08-05 11:49 ` Vlastimil Babka
2022-08-05 12:09 ` David Hildenbrand
2022-08-05 13:38 ` Vlastimil Babka
2022-08-05 14:22 ` David Hildenbrand
2022-08-05 14:53 ` Dave Hansen
2022-08-05 14:41 ` Dave Hansen
2022-08-05 18:17 ` Vlastimil Babka
2022-08-08 15:55 ` Dave Hansen
2022-08-10 14:19 ` Mel Gorman
2022-08-15 21:08 ` Dionna Amalie Glaze
2022-08-15 22:02 ` Tom Lendacky
2022-08-29 16:02 ` Dionna Amalie Glaze
2022-08-29 16:19 ` Dave Hansen
2022-09-06 17:50 ` Dionna Amalie Glaze
2022-09-08 12:11 ` Mike Rapoport
2022-09-08 16:23 ` Dionna Amalie Glaze
2022-09-08 19:28 ` Mike Rapoport
2022-09-22 14:31 ` Tom Lendacky
2022-09-24 1:03 ` Kirill A. Shutemov
2022-09-24 9:36 ` Mike Rapoport
2022-09-26 12:10 ` Kirill A. Shutemov
2022-09-26 13:38 ` Tom Lendacky
2022-09-26 15:42 ` Kirill A. Shutemov
2022-09-26 15:42 ` Tom Lendacky
2022-06-14 12:02 ` [PATCHv7 03/14] mm: Report unaccepted memory in meminfo Kirill A. Shutemov
2022-07-26 14:33 ` David Hildenbrand
2022-06-14 12:02 ` [PATCHv7 04/14] efi/x86: Get full memory map in allocate_e820() Kirill A. Shutemov
2022-07-25 13:02 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 05/14] x86/boot: Add infrastructure required for unaccepted memory support Kirill A. Shutemov
2022-06-15 10:19 ` Peter Zijlstra
2022-06-15 15:05 ` Kirill A. Shutemov
2022-07-17 17:16 ` Borislav Petkov
2022-07-25 21:33 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 06/14] efi/x86: Implement support for unaccepted memory Kirill A. Shutemov
2022-06-22 19:58 ` Dave Hansen
2022-07-26 8:35 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 07/14] x86/boot/compressed: Handle " Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 08/14] x86/mm: Reserve unaccepted memory bitmap Kirill A. Shutemov
2022-07-26 9:07 ` Borislav Petkov
2022-11-30 1:28 ` Kirill A. Shutemov
2022-12-01 9:37 ` Mike Rapoport
2022-12-01 13:47 ` Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 09/14] x86/mm: Provide helpers for unaccepted memory Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 10/14] x86/mm: Avoid load_unaligned_zeropad() stepping into " Kirill A. Shutemov
2022-06-23 17:19 ` Dave Hansen
2022-07-26 10:21 ` Borislav Petkov
2022-08-02 23:46 ` Dave Hansen
2022-08-03 14:02 ` Dave Hansen
2022-08-11 11:26 ` Borislav Petkov
2022-08-13 16:11 ` Andy Lutomirski
2022-08-13 21:13 ` Kirill A. Shutemov
2022-08-13 16:04 ` Andy Lutomirski
2022-08-13 20:58 ` Kirill A. Shutemov
2022-07-26 17:25 ` Borislav Petkov
2022-07-26 17:46 ` Dave Hansen
2022-07-26 20:17 ` Andy Lutomirski
2022-08-09 11:38 ` Kirill A. Shutemov
2022-08-13 16:03 ` Andy Lutomirski
2022-08-13 21:02 ` Kirill A. Shutemov
2022-06-14 12:02 ` [PATCHv7 11/14] x86: Disable kexec if system has " Kirill A. Shutemov
2022-06-23 17:23 ` Dave Hansen
2022-06-23 21:48 ` Eric W. Biederman
2022-06-24 2:00 ` Kirill A. Shutemov
2022-06-28 23:51 ` Kirill A. Shutemov
2022-06-29 0:10 ` Dave Hansen
2022-06-29 0:59 ` Kirill A. Shutemov
2022-07-04 7:18 ` Dave Young
2022-06-14 12:02 ` [PATCHv7 12/14] x86/tdx: Make _tdx_hypercall() and __tdx_module_call() available in boot stub Kirill A. Shutemov
2022-06-23 17:25 ` Dave Hansen
2022-06-14 12:02 ` [PATCHv7 13/14] x86/tdx: Refactor try_accept_one() Kirill A. Shutemov
2022-06-23 17:31 ` Dave Hansen
2022-07-26 10:58 ` Borislav Petkov
2022-06-14 12:02 ` [PATCHv7 14/14] x86/tdx: Add unaccepted memory support Kirill A. Shutemov
2022-06-24 16:22 ` Dave Hansen
2022-06-27 10:42 ` Kirill A. Shutemov
2022-07-26 14:51 ` Borislav Petkov
2022-08-09 11:45 ` Kirill A. Shutemov
2022-08-10 10:27 ` Borislav Petkov
2022-06-24 16:37 ` [PATCHv7 00/14] mm, x86/cc: Implement support for unaccepted memory Peter Gonda
2022-06-24 16:57 ` Dave Hansen
2022-06-24 17:06 ` Marc Orr
2022-06-24 17:09 ` Dave Hansen
2022-06-24 17:15 ` Peter Gonda
2022-06-24 17:19 ` Marc Orr
2022-06-24 17:21 ` Peter Gonda
2022-06-24 17:47 ` Dave Hansen
2022-06-24 18:10 ` Peter Gonda
2022-06-24 18:13 ` Dave Hansen
2022-06-24 17:40 ` Michael Roth
2022-06-24 17:58 ` Michael Roth
2022-06-24 18:05 ` Peter Gonda
2022-06-27 11:30 ` Kirill A. Shutemov
2022-06-27 11:54 ` Ard Biesheuvel
2022-06-27 12:22 ` Kirill A. Shutemov
2022-06-27 16:17 ` Peter Gonda [this message]
2022-06-27 16:33 ` Ard Biesheuvel
2022-06-27 22:38 ` Kirill A. Shutemov
2022-06-28 17:17 ` Ard Biesheuvel
2022-07-18 17:21 ` Kirill A. Shutemov
2022-07-18 23:32 ` Dionna Amalie Glaze
2022-07-19 0:31 ` Dionna Amalie Glaze
2022-07-19 18:29 ` Dionna Amalie Glaze
2022-07-19 19:13 ` Borislav Petkov
2022-07-19 20:45 ` Ard Biesheuvel
2022-07-19 21:23 ` Borislav Petkov
2022-07-19 21:35 ` Dave Hansen
2022-07-19 21:50 ` Borislav Petkov
2022-07-19 22:01 ` Kirill A. Shutemov
2022-07-19 22:02 ` Dave Hansen
2022-07-19 22:08 ` Tom Lendacky
2022-07-20 0:26 ` Marc Orr
2022-07-20 5:44 ` Borislav Petkov
2022-07-20 17:03 ` Marc Orr
2022-07-22 15:07 ` Borislav Petkov
2022-07-21 17:12 ` Dave Hansen
2022-07-23 11:14 ` Ard Biesheuvel
2022-07-28 22:01 ` Dionna Amalie Glaze
2022-08-09 11:14 ` Kirill A. Shutemov
2022-08-09 11:36 ` Ard Biesheuvel
2022-08-09 11:54 ` Kirill A. Shutemov
2022-08-09 21:09 ` Dionna Amalie Glaze
2022-07-19 2:48 ` Yao, Jiewen
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