Re: [PATCH 1/5] KVM: rseq: Update rseq when processing NOTIFY_RESUME on xfer to KVM guest
From: Sean Christopherson <seanjc@google.com>
Date: 2021-09-07 14:38:39
Also in:
kvm, linux-arm-kernel, linux-kselftest, linux-mips, linux-s390, lkml
On Mon, Sep 06, 2021, Paolo Bonzini wrote:
On 20/08/21 20:51, Mathieu Desnoyers wrote:quoted
quoted
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.quoted
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)?
Made it all the way to v3 while you were out :-) https://lkml.kernel.org/r/20210901203030.1292304-1-seanjc@google.com