From: Borislav Petkov <bp@alien8.de>
To: Michael Roth <michael.roth@amd.com>,
Josh Poimboeuf <jpoimboe@kernel.org>
Cc: bp@kernel.org, bgardon@google.com, dave.hansen@linux.intel.com,
dmatlack@google.com, hpa@zytor.com, jpoimboe@kernel.org,
kvm@vger.kernel.org, leitao@debian.org,
linux-kernel@vger.kernel.org, maz@kernel.org, mingo@redhat.com,
mirsad.todorovac@alu.unizg.hr, pawan.kumar.gupta@linux.intel.com,
pbonzini@redhat.com, peterz@infradead.org, seanjc@google.com,
shahuang@redhat.com, tabba@google.com, tglx@linutronix.de,
x86@kernel.org
Subject: Re: [BUG net-next] arch/x86/kernel/cpu/bugs.c:2935: "Unpatched return thunk in use. This should not happen!" [STACKTRACE]
Date: Wed, 3 Apr 2024 14:14:36 +0200 [thread overview]
Message-ID: <20240403121436.GDZg1ILCn0a4Ddif3g@fat_crate.local> (raw)
In-Reply-To: <20240402133856.dtzinbbudsu7rg7d@amd.com>
On Tue, Apr 02, 2024 at 08:38:56AM -0500, Michael Roth wrote:
> On Tue, Apr 02, 2024 at 12:15:49PM +0200, bp@kernel.org wrote:
> > From: Borislav Petkov <bp@alien8.de>
> >
> > Sorry if this comes out weird - mail troubles currently.
> >
> > On Thu, Mar 28, 2024 at 07:38:30AM -0500, Michael Roth wrote:
> > > I'm seeing it pretty consistently on kvm/next as well. Not sure if
> > > there's anything special about my config but starting a fairly basic
> > > SVM guest seems to be enough to trigger it for me on the first
> > > invocation of svm_vcpu_run().
> >
> > Hmm, can you share your config and what exactly you're doing?
> >
> > I can't reproduce with Mirsad's reproducer, probably because of .config
> > differences. I tried making all CONFIG*KVM* options =y but no
> > difference.
>
> I've reproduced against tip/master from today and attached the host
> config I used.
>
> I can reproduce with a normal SVM guest using the following cmdline,
> but I don't think there's anything particular special regarding what
> QEMU options you use. It seems to trigger on the very first entry into
> VMRUN path:
>
> /home/mroth/qemu-build-snp-v4-wip2/qemu-system-x86_64
> -smp 32,maxcpus=255 -cpu EPYC-Milan-v2 -overcommit cpu-pm=off
> -enable-kvm -m 4G,slots=5,maxmem=210G -vga std -nographic
> -machine pc,memory-backend=ram1
> -object memory-backend-memfd,id=ram1,size=4G,share=true,prealloc=false,reserve=false
> -device virtio-scsi-pci,id=scsi0,disable-legacy=on,iommu_platform=true
> -drive file=/home/mroth/ubuntu-18.04-seves2.qcow2,if=none,id=drive0,snapshot=on
> -device scsi-hd,id=hd0,drive=drive0,bus=scsi0.0
> -device virtio-net-pci,mac=52:54:00:6c:3c:01,netdev=netdev0,id=net0,disable-legacy=on,iommu_platform=true,romfile=
> -netdev tap,script=/home/mroth/qemu-ifup,id=netdev0
> -L /home/mroth/AMDSEV/snp-release-2024-02-22/usr/local/share/qemu
> -msg timestamp=on
> -drive if=pflash,format=raw,unit=0,file=/home/mroth/AMDSEV/snp-release-2024-02-22/usr/local/share/qemu/OVMF_CODE.fd,readonly=on
> -drive if=pflash,format=raw,unit=1,file=/home/mroth/AMDSEV/snp-release-2024-02-22/usr/local/share/qemu/OVMF_VARS.fd
>
> I can also trigger using one of the more basic KVM selftests:
>
> make INSTALL_HDR_PATH="$headers_dir" headers_install
> make -C tools/testing/selftests TARGETS="kvm" EXTRA_CFLAGS="-DDEBUG -I$headers_dir"
> sudo tools/testing/selftests/kvm/userspace_io_test
Ok, thanks, that helped.
Problem is:
7f4b5cde2409 ("kvm: Disable objtool frame pointer checking for vmenter.S")
it is disabling checking of the arch/x86/kvm/svm/vmenter.S by objtool
when CONFIG_FRAME_POINTER=y but that also leads to objtool *not*
generating .return_sites and the return thunk remains unpatched.
I think we need to say: ignore frame pointer checking but still generate
.return_sites.
Josh, ideas?
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2024-04-03 12:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-18 19:47 [BUG net-next] arch/x86/kernel/cpu/bugs.c:2935: "Unpatched return thunk in use. This should not happen!" [STACKTRACE] Mirsad Todorovac
2024-03-18 20:21 ` Borislav Petkov
2024-03-20 1:28 ` Mirsad Todorovac
2024-03-26 10:16 ` Borislav Petkov
2024-03-26 19:15 ` Mirsad Todorovac
2024-03-28 12:38 ` Michael Roth
2024-04-02 10:15 ` bp
2024-04-02 13:38 ` Michael Roth
2024-04-03 12:14 ` Borislav Petkov [this message]
2024-04-03 12:48 ` Sean Christopherson
2024-04-04 13:44 ` Borislav Petkov
2024-04-17 15:52 ` Paolo Bonzini
[not found] ` <f497a833-f945-4907-b916-1739324de014@alu.unizg.hr>
2024-04-04 13:41 ` Borislav Petkov
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