From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Dionna Glaze <dionnaglaze@google.com>,
linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
x86@kernel.org, jiewen.yao@intel.com, devel@edk2.groups.io,
Ard Biescheuvel <ardb@kernel.org>,
"Min M. Xu" <min.m.xu@intel.org>,
James Bottomley <jejb@linux.ibm.com>,
Tom Lendacky <Thomas.Lendacky@amd.com>,
Erdem Aktas <erdemaktas@google.com>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [PATCH v2] x86/efi: Safely enable unaccepted memory in UEFI
Date: Mon, 16 Jan 2023 15:30:57 +0300 [thread overview]
Message-ID: <20230116123057.wvr6rz7y3ubgcm5z@box.shutemov.name> (raw)
In-Reply-To: <20230116105648.63hsxnmj2juwudmu@sirius.home.kraxel.org>
On Mon, Jan 16, 2023 at 11:56:48AM +0100, Gerd Hoffmann wrote:
> On Sat, Jan 14, 2023 at 01:20:24AM +0300, Kirill A. Shutemov wrote:
> > On Fri, Jan 13, 2023 at 09:29:26PM +0000, Dionna Glaze wrote:
> > > This patch depends on Kirill A. Shutemov's series
> > >
> > > [PATCHv8 00/14] mm, x86/cc: Implement support for unaccepted memory
> > >
> > > The UEFI v2.9 specification includes a new memory type to be used in
> > > environments where the OS must accept memory that is provided from its
> > > host. Before the introduction of this memory type, all memory was
> > > accepted eagerly in the firmware. In order for the firmware to safely
> > > stop accepting memory on the OS's behalf, the OS must affirmatively
> > > indicate support to the firmware.
> >
> > I think it is a bad idea.
> >
> > This approach breaks use case with a bootloader between BIOS and OS.
> > As the bootloader does ExitBootServices() it has to make the call on
> > behalf of OS when it has no idea if the OS supports unaccepted.
>
> Nothing breaks, it'll error on the safe side. If the protocol callback
> is not called the firmware will simply accept all memory. The guest OS
> will only see unaccepted memory if it explicitly asked for it (assuming
> the firmware wants know to support both cases, of course the firmware
> could also enforce the one or the other and just not offer the
> protocol).
How bootloader suppose to know if OS will ask for unaccepted memory?
It can't. It means the use-case with bootloader cannot ever use
unaccepted memory. That's broken design.
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2023-01-16 12:31 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-13 21:29 [PATCH v2] x86/efi: Safely enable unaccepted memory in UEFI Dionna Glaze
2023-01-13 22:20 ` Kirill A. Shutemov
2023-01-16 10:56 ` Gerd Hoffmann
2023-01-16 12:30 ` Kirill A. Shutemov [this message]
2023-01-16 13:11 ` Ard Biesheuvel
2023-01-16 13:42 ` Kirill A. Shutemov
2023-01-16 19:43 ` Dionna Glaze
2023-01-16 23:17 ` Kirill A. Shutemov
2023-01-17 10:24 ` Gerd Hoffmann
2023-01-17 16:45 ` Dionna Glaze
2023-01-18 7:51 ` [edk2-devel] " Gerd Hoffmann
2023-01-16 21:22 ` Dave Hansen
2023-01-16 22:46 ` Lendacky, Thomas
2023-01-18 15:09 ` Ard Biesheuvel
2023-01-18 15:40 ` Dave Hansen
2023-01-18 15:46 ` Ard Biesheuvel
2023-01-17 10:34 ` Gerd Hoffmann
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-list from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20230116123057.wvr6rz7y3ubgcm5z@box.shutemov.name \
--to=devel@edk2.groups.io \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox