Re: [PATCH 0/5] KVM: rseq: Fix and a test for a KVM+rseq bug

From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>, Guo Ren <guoren@kernel.org>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Heiko Carstens <hca@linux.ibm.com>,
	Vasily Gorbik <gor@linux.ibm.com>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Oleg Nesterov <oleg@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Peter Zijlstra <peterz@infradead.org>,
	Andy Lutomirski <luto@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Boqun Feng <boqun.feng@gmail.com>, Shuah Khan <shuah@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org, linux-csky@vger.kernel.org,
	linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
	linux-s390@vger.kernel.org, kvm@vger.kernel.org,
	linux-kselftest@vger.kernel.org, Peter Foley <pefoley@google.com>,
	Shakeel Butt <shakeelb@google.com>,
	Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH 0/5] KVM: rseq: Fix and a test for a KVM+rseq bug
Date: Wed, 22 Sep 2021 16:12:38 +0200	[thread overview]
Message-ID: <430684f9-1b35-b6f1-f243-6298e892bc7a@redhat.com> (raw)
In-Reply-To: <20210818001210.4073390-1-seanjc@google.com>

On 18/08/21 02:12, Sean Christopherson wrote:
> Patch 1 fixes a KVM+rseq bug where KVM's handling of TIF_NOTIFY_RESUME,
> e.g. for task migration, clears the flag without informing rseq and leads
> to stale data in userspace's rseq struct.
> 
> Patch 2 is a cleanup to try and make future bugs less likely.  It's also
> a baby step towards moving and renaming tracehook_notify_resume() since
> it has nothing to do with tracing.  It kills me to not do the move/rename
> as part of this series, but having a dedicated series/discussion seems
> more appropriate given the sheer number of architectures that call
> tracehook_notify_resume() and the lack of an obvious home for the code.
> 
> Patch 3 is a fix/cleanup to stop overriding x86's unistd_{32,64}.h when
> the include path (intentionally) omits tools' uapi headers.  KVM's
> selftests do exactly that so that they can pick up the uapi headers from
> the installed kernel headers, and still use various tools/ headers that
> mirror kernel code, e.g. linux/types.h.  This allows the new test in
> patch 4 to reference __NR_rseq without having to manually define it.
> 
> Patch 4 is a regression test for the KVM+rseq bug.
> 
> Patch 5 is a cleanup made possible by patch 3.
> 
> 
> Sean Christopherson (5):
>    KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM
>      guest
>    entry: rseq: Call rseq_handle_notify_resume() in
>      tracehook_notify_resume()
>    tools: Move x86 syscall number fallbacks to .../uapi/
>    KVM: selftests: Add a test for KVM_RUN+rseq to detect task migration
>      bugs
>    KVM: selftests: Remove __NR_userfaultfd syscall fallback
> 
>   arch/arm/kernel/signal.c                      |   1 -
>   arch/arm64/kernel/signal.c                    |   1 -
>   arch/csky/kernel/signal.c                     |   4 +-
>   arch/mips/kernel/signal.c                     |   4 +-
>   arch/powerpc/kernel/signal.c                  |   4 +-
>   arch/s390/kernel/signal.c                     |   1 -
>   include/linux/tracehook.h                     |   2 +
>   kernel/entry/common.c                         |   4 +-
>   kernel/rseq.c                                 |   4 +-
>   .../x86/include/{ => uapi}/asm/unistd_32.h    |   0
>   .../x86/include/{ => uapi}/asm/unistd_64.h    |   3 -
>   tools/testing/selftests/kvm/.gitignore        |   1 +
>   tools/testing/selftests/kvm/Makefile          |   3 +
>   tools/testing/selftests/kvm/rseq_test.c       | 131 ++++++++++++++++++
>   14 files changed, 143 insertions(+), 20 deletions(-)
>   rename tools/arch/x86/include/{ => uapi}/asm/unistd_32.h (100%)
>   rename tools/arch/x86/include/{ => uapi}/asm/unistd_64.h (83%)
>   create mode 100644 tools/testing/selftests/kvm/rseq_test.c
> 

Queued v3, thanks.  I'll send it in a separate pull request to Linus 
since it touches stuff outside my usual turf.

Thanks,

Paolo