From: Joerg Roedel <jroedel@suse.de>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Arvind Sankar <nivedita@alum.mit.edu>,
x86@kernel.org, linux-kernel@vger.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Kees Cook <keescook@chromium.org>
Subject: Re: RFC x86/boot/64: BOOT_PGT_SIZE definition for compressed kernel
Date: Tue, 27 Oct 2020 16:46:58 +0100 [thread overview]
Message-ID: <20201027154658.GG22179@suse.de> (raw)
In-Reply-To: <20201027124007.xkkseswwgerlzlsl@box>
On Tue, Oct 27, 2020 at 03:40:07PM +0300, Kirill A. Shutemov wrote:
> BTW, what happens if we underestimate BOOT_PGT_SIZE? Do we overwrite
> something?
The boot code will print an error and stop the machine when allocating a
page-table page fails.
I also think that bumping BOOT_PGT_SIZE up to have more pages available
is a good short-term solution. Recycling pages will also need to take
page encryption attributes into account, as for SEV-ES the GHCB page
needs to be mapped unencrypted.
Another option to safe some memory is to make use of GB pages in the
decompression code. Machines where the current BOOT_PGT_SIZE is too
small will likely support GB pages too.
Regards,
Joerg
prev parent reply other threads:[~2020-10-27 16:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-25 0:41 RFC x86/boot/64: BOOT_PGT_SIZE definition for compressed kernel Arvind Sankar
2020-10-25 2:20 ` Arvind Sankar
2020-10-27 12:40 ` Kirill A. Shutemov
2020-10-27 13:16 ` Arvind Sankar
2020-10-27 14:31 ` Kirill A. Shutemov
2020-10-27 15:46 ` Joerg Roedel [this message]
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