From: "Gerd Hoffmann" <kraxel@redhat.com>
To: Laszlo Ersek <lersek@redhat.com>
Cc: devel@edk2.groups.io, Ard Biesheuvel <ardb+tianocore@kernel.org>,
Brijesh Singh <brijesh.singh@amd.com>,
Erdem Aktas <erdemaktas@google.com>,
James Bottomley <jejb@linux.ibm.com>,
Jiewen Yao <jiewen.yao@intel.com>,
Jordan Justen <jordan.l.justen@intel.com>,
Min Xu <min.m.xu@intel.com>,
Sebastien Boeuf <sebastien.boeuf@intel.com>,
Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH 1/1] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg block regression
Date: Thu, 5 Jan 2023 14:12:56 +0100 [thread overview]
Message-ID: <20230105131256.m3tgqu4antgrk7rt@sirius.home.kraxel.org> (raw)
In-Reply-To: <20230104151234.286030-2-lersek@redhat.com>
On Wed, Jan 04, 2023 at 04:12:34PM +0100, Laszlo Ersek wrote:
> In QEMU v5.1.0, the CPU hotplug register block misbehaves: the negotiation
> protocol is (effectively) broken such that it suggests that switching from
> the legacy interface to the modern interface works, but in reality the
> switch never happens. The symptom has been witnessed when using TCG
> acceleration; KVM seems to mask the issue. The issue persists with the
> following (latest) stable QEMU releases: v5.2.0, v6.2.0, v7.2.0. Currently
> there is no stable release that addresses the problem.
>
> The QEMU bug confuses the Present and Possible counting in function
> PlatformMaxCpuCountInitialization(), in
> "OvmfPkg/Library/PlatformInitLib/Platform.c". OVMF ends up with Present=0
> Possible=1. This in turn further confuses MpInitLib in UefiCpuPkg (hence
> firmware-time multiprocessing will be broken). Worse, CPU hot(un)plug with
> SMI will be summarily broken in OvmfPkg/CpuHotplugSmm, which (considering
> the privilege level of SMM) is not that great.
>
> Detect the issue in PlatformMaxCpuCountInitialization(), and print an
> error message and *hang* if the issue is present.
>
> The problem was originally reported by Ard [0]. We analyzed it at [1] and
> [2]. A QEMU patch was sent at [3].
>
> [0] https://bugzilla.tianocore.org/show_bug.cgi?id=4234#c2
>
> [1] https://bugzilla.tianocore.org/show_bug.cgi?id=4234#c3
>
> [2] IO port write width clamping differs between TCG and KVM
> http://mid.mail-archive.com/aaedee84-d3ed-a4f9-21e7-d221a28d1683@redhat.com
> https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg00199.html
>
> [3] acpi: cpuhp: fix guest-visible maximum access size to the legacy reg block
> http://mid.mail-archive.com/20230104090138.214862-1-lersek@redhat.com
> https://lists.gnu.org/archive/html/qemu-devel/2023-01/msg00278.html
>
> NOTE: PlatformInitLib is used in the following platform DSCs:
>
> OvmfPkg/AmdSev/AmdSevX64.dsc
> OvmfPkg/CloudHv/CloudHvX64.dsc
> OvmfPkg/IntelTdx/IntelTdxX64.dsc
> OvmfPkg/Microvm/MicrovmX64.dsc
> OvmfPkg/OvmfPkgIa32.dsc
> OvmfPkg/OvmfPkgIa32X64.dsc
> OvmfPkg/OvmfPkgX64.dsc
>
> but I can only test this change with the last three platforms, running on
> QEMU.
>
> Test results:
>
> TCG QEMU OVMF result
> patched patched
> --- ------- ------- -------------------------------------------------
> 0 0 0 CPU counts OK (KVM masks the QEMU bug)
> 0 0 1 CPU counts OK (KVM masks the QEMU bug)
> 0 1 0 CPU counts OK (QEMU fix, but KVM masks the QEMU
> bug anyway)
> 0 1 1 CPU counts OK (QEMU fix, but KVM masks the QEMU
> bug anyway)
> 1 0 0 boot with broken CPU counts (original QEMU bug)
> 1 0 1 broken CPU count caught (boot hangs)
> 1 1 0 CPU counts OK (QEMU fix)
> 1 1 1 CPU counts OK (QEMU fix)
>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Brijesh Singh <brijesh.singh@amd.com>
> Cc: Erdem Aktas <erdemaktas@google.com>
> Cc: Gerd Hoffmann <kraxel@redhat.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Jiewen Yao <jiewen.yao@intel.com>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Min Xu <min.m.xu@intel.com>
> Cc: Sebastien Boeuf <sebastien.boeuf@intel.com>
> Cc: Tom Lendacky <thomas.lendacky@amd.com>
> Bugzilla: https://bugzilla.tianocore.org/show_bug.cgi?id=4250
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
next prev parent reply other threads:[~2023-01-05 13:13 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-04 15:12 [PATCH 0/1] OvmfPkg/PlatformInitLib: catch QEMU's CPU hotplug reg block regression Laszlo Ersek
2023-01-04 15:12 ` [PATCH 1/1] " Laszlo Ersek
2023-01-05 13:12 ` Gerd Hoffmann [this message]
2023-01-04 23:34 ` [edk2-devel] [PATCH 0/1] " Michael D Kinney
2023-01-05 5:39 ` Guo, Gua
2023-01-05 15:15 ` Laszlo Ersek
2023-01-05 15:17 ` Laszlo Ersek
2023-01-05 13:12 ` Gerd Hoffmann
2023-01-05 13:43 ` Oliver Steffen
2023-01-05 13:52 ` Gerd Hoffmann
2023-01-05 15:12 ` Laszlo Ersek
2023-01-05 15:18 ` Oliver Steffen
[not found] ` <173772B56BF8C7B8.2132@groups.io>
2023-01-09 9:49 ` [edk2-devel] " Oliver Steffen
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=20230105131256.m3tgqu4antgrk7rt@sirius.home.kraxel.org \
--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