From: Borislav Petkov <bp@alien8.de>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: "Jörg Rödel" <joro@8bytes.org>,
"Tom Lendacky" <thomas.lendacky@amd.com>,
"Tao Liu" <ltao@redhat.com>,
"Michael Roth" <michael.roth@amd.com>,
tglx@linutronix.de, mingo@redhat.com,
dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com,
linux-kernel@vger.kernel.org, bhe@redhat.com, dyoung@redhat.com,
kexec@lists.infradead.org, linux-efi@vger.kernel.org
Subject: Re: [PATCH v2] x86/kexec: Add EFI config table identity mapping for kexec kernel
Date: Sat, 5 Aug 2023 11:17:38 +0200 [thread overview]
Message-ID: <20230805091738.GAZM4TslVWR3HHKeUC@fat_crate.local> (raw)
In-Reply-To: <CAMj1kXHnSzdQw5CMAVXU7EzpnrdRvAqKZVgA+EV35kHmwVULgQ@mail.gmail.com>
On Thu, Aug 03, 2023 at 01:11:54PM +0200, Ard Biesheuvel wrote:
> Sadly, not only 'old' grubs - GRUB mainline only recently added
> support for booting Linux/x86 via the EFI stub (because I wrote the
> code for them),
haha.
> but it will still fall back to the previous mode for kernels that are
> built without EFI stub support, or which are older than ~v5.8 (because
> their EFI stub does not implement the generic EFI initrd loading
> mechanism)
The thing is, those SNP kernels pretty much use the EFI boot mechanism.
I mean, don't take my word for it as I run SNP guests only from time to
time but that's what everyone uses AFAIK.
> Yeah. what seems to be saving our ass here is that startup_32 maps the
> first 1G of physical address space 4 times, and x86_64 EFI usually
> puts firmware tables below 4G. This means the cc blob check doesn't
> fault, but it may dereference bogus memory traversing the config table
> array looking for the cc blob GUID. However, the system table field
> holding the size of the array may also appear as bogus so this may
> still break in weird ways.
Oh fun.
> I don't think we can kill it yet, but it would be nice if we could
> avoid the need to support SNP boot when entering that way.
That's what I meant - not boot SNP guests through the 32-bit entry path.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-08-05 9:18 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-01 7:20 [PATCH v2] x86/kexec: Add EFI config table identity mapping for kexec kernel Tao Liu
2023-06-01 8:13 ` Baoquan He
2023-06-01 8:25 ` Tao Liu
2023-06-08 7:13 ` Tao Liu
2023-06-16 12:24 ` Baoquan He
2023-07-05 17:33 ` Borislav Petkov
2023-07-07 2:47 ` Dave Young
2023-07-07 3:38 ` Tao Liu
2023-07-07 4:23 ` Baoquan He
2023-07-07 8:22 ` Joerg Roedel
2023-07-07 8:41 ` Baoquan He
2023-07-07 8:57 ` Borislav Petkov
2023-07-07 15:25 ` Michael Roth
2023-07-07 17:12 ` Borislav Petkov
2023-07-13 10:17 ` Ard Biesheuvel
2023-07-17 15:02 ` Tao Liu
2023-07-07 15:46 ` Tom Lendacky
2023-07-13 10:04 ` Borislav Petkov
2023-07-17 13:53 ` Tao Liu
2023-07-17 14:14 ` Borislav Petkov
2023-07-17 14:24 ` Tao Liu
2023-07-27 11:03 ` Tao Liu
2023-07-28 16:55 ` Borislav Petkov
2023-08-02 8:22 ` Tao Liu
2023-08-02 9:39 ` Borislav Petkov
2023-08-02 13:40 ` Tom Lendacky
2023-08-02 13:58 ` Borislav Petkov
2023-08-02 14:55 ` Ard Biesheuvel
2023-08-02 15:51 ` Borislav Petkov
2023-08-03 11:11 ` Ard Biesheuvel
2023-08-03 14:27 ` Ard Biesheuvel
2023-08-05 9:19 ` Borislav Petkov
2023-08-05 9:17 ` Borislav Petkov [this message]
2023-08-06 9:00 ` Ard Biesheuvel
2023-07-17 14:56 ` Ard Biesheuvel
2023-07-17 15:11 ` Tao Liu
2023-07-27 11:11 ` Tao Liu
2023-08-07 16:17 ` [tip: x86/urgent] x86/sev: Do not try to parse for the CC blob on non-AMD hardware tip-bot2 for Borislav Petkov (AMD)
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