From: Paolo Bonzini <pbonzini@redhat.com>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
Sean Christopherson <seanjc@google.com>
Cc: "Russell King, ARM Linux" <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>, gor <gor@linux.ibm.com>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Oleg Nesterov <oleg@redhat.com>, rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Andy Lutomirski <luto@kernel.org>, paulmck <paulmck@kernel.org>,
Boqun Feng <boqun.feng@gmail.com>, shuah <shuah@kernel.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
linux-kernel <linux-kernel@vger.kernel.org>,
linux-csky <linux-csky@vger.kernel.org>,
linux-mips <linux-mips@vger.kernel.org>,
linuxppc-dev <linuxppc-dev@lists.ozlabs.org>,
linux-s390 <linux-s390@vger.kernel.org>,
KVM list <kvm@vger.kernel.org>,
linux-kselftest <linux-kselftest@vger.kernel.org>,
Peter Foley <pefoley@google.com>,
Shakeel Butt <shakeelb@google.com>,
Ben Gardon <bgardon@google.com>
Subject: Re: [PATCH 1/5] KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest
Date: Mon, 6 Sep 2021 12:28:12 +0200 [thread overview]
Message-ID: <425456d3-4772-2a1b-9cf3-a5b750b95c2e@redhat.com> (raw)
In-Reply-To: <1872633041.20290.1629485463253.JavaMail.zimbra@efficios.com>
On 20/08/21 20:51, Mathieu Desnoyers wrote:
>> Ah, or is it the case that rseq_cs is non-NULL if and only if userspace is in an
>> rseq critical section, and because syscalls in critical sections are illegal, by
>> definition clearing rseq_cs is a nop unless userspace is misbehaving.
> Not quite, as I described above. But we want it to stay set so the CONFIG_DEBUG_RSEQ
> code executed when returning from ioctl to userspace will be able to validate that
> it is not nested within a rseq critical section.
>
>> If that's true, what about explicitly checking that at NOTIFY_RESUME? Or is it
>> not worth the extra code to detect an error that will likely be caught anyways?
> The error will indeed already be caught on return from ioctl to userspace, so I
> don't see any added value in duplicating this check.
Sean, can you send a v2 (even for this patch only would be okay)?
Thanks,
Paolo
next prev parent reply other threads:[~2021-09-06 10:29 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 0:12 [PATCH 0/5] KVM: rseq: Fix and a test for a KVM+rseq bug Sean Christopherson
2021-08-18 0:12 ` [PATCH 1/5] KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest Sean Christopherson
2021-08-19 21:39 ` Mathieu Desnoyers
2021-08-19 23:48 ` Sean Christopherson
2021-08-20 18:51 ` Mathieu Desnoyers
2021-08-20 22:26 ` Sean Christopherson
2021-09-06 10:28 ` Paolo Bonzini [this message]
2021-09-07 14:38 ` Sean Christopherson
2021-08-18 0:12 ` [PATCH 2/5] entry: rseq: Call rseq_handle_notify_resume() in tracehook_notify_resume() Sean Christopherson
2021-08-19 21:41 ` Mathieu Desnoyers
2021-08-18 0:12 ` [PATCH 3/5] tools: Move x86 syscall number fallbacks to .../uapi/ Sean Christopherson
2021-08-18 0:12 ` [PATCH 4/5] KVM: selftests: Add a test for KVM_RUN+rseq to detect task migration bugs Sean Christopherson
2021-08-19 21:52 ` Mathieu Desnoyers
2021-08-19 23:33 ` Sean Christopherson
2021-08-20 18:31 ` Mathieu Desnoyers
2021-08-20 22:25 ` Sean Christopherson
2021-08-18 0:12 ` [PATCH 5/5] KVM: selftests: Remove __NR_userfaultfd syscall fallback Sean Christopherson
2021-09-22 14:12 ` [PATCH 0/5] KVM: rseq: Fix and a test for a KVM+rseq bug Paolo Bonzini
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