From: Jarkko Sakkinen <jarkko@kernel.org>
To: Sean Christopherson <seanjc@google.com>,
Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@zeniv.linux.org.uk>,
Dan Williams <dan.j.williams@intel.com>,
Borislav Petkov <bp@alien8.de>,
LKML <linux-kernel@vger.kernel.org>,
the arch/x86 maintainers <x86@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>
Subject: Re: [patch 01/10] x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user()
Date: Thu, 02 Sep 2021 16:08:11 +0300 [thread overview]
Message-ID: <84fd35193e293894c4e64704e18dc063995b62c0.camel@kernel.org> (raw)
In-Reply-To: <YS+upEmTfpZub3s9@google.com>
On Wed, 2021-09-01 at 16:47 +0000, Sean Christopherson wrote:
> On Wed, Sep 01, 2021, Thomas Gleixner wrote:
> > On Wed, Sep 01 2021 at 14:00, Thomas Gleixner wrote:
> > > commit b2f9d678e28c ("x86/mce: Check for faults tagged in
> > > EXTABLE_CLASS_FAULT exception table entries") made use of this in MCE to
> > > allow in kernel recovery. The only thing it uses is checking the
> > > exception handler type.
> > >
> > > Bah. I'll fix that up to make that less obscure.
> > >
> > > The remaining two use cases (SGX and FPU) make use of the stored trap
> > > number.
> >
> > Though while for the FPU use case we really want to handle the #MC case,
> > it's not clear to me whether this is actually correct for SGX.
> >
> > Jarkko, Sean, Dave?
>
> Are you asking about #MC specifically, or about SGX consuming the trap number in
> general?
>
> For #MC, it's probably a moot point because #MC on ENCLS is not recoverable for
> current hardware. If #MC somehow occurs on ENCLS and doesn't kill the platform,
> "handling" the #MC in SGX is probably wrong. Note, Tony is working on a series to
> support recoverable #MC on SGX stuff on future hardware[*], but I'm not sure that's
> relevant to this discussion.
>
> As for SGX consuming the trap number in general, it's correct. For non-KVM usage,
> it's nice to have but not strictly necessary. Any fault except #PF on ENCLS is
> guaranteed to be a kernel or hardware bug; SGX uses the trap number to WARN on a
> !#PF exception, e.g. on #GP or #UD. Not having the trap number would mean losing
> those sanity checks, which have been useful in the past.
AFAIK, we do not consider #UD as a bug. Agree with the conclusion that SGX
should never #MC, I just did not get this part. #UD is something that is
useful for SGX run-time.
/Jarkko
next prev parent reply other threads:[~2021-09-02 13:08 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-30 16:27 [patch 00/10] x86/fpu: Clean up error handling in sigframe related code Thomas Gleixner
2021-08-30 16:27 ` [patch 01/10] x86/fpu/signal: Clarify exception handling in restore_fpregs_from_user() Thomas Gleixner
2021-08-30 19:33 ` Borislav Petkov
2021-08-30 20:07 ` Borislav Petkov
2021-08-30 20:09 ` Thomas Gleixner
2021-08-30 21:02 ` Al Viro
2021-08-30 21:26 ` Linus Torvalds
2021-08-30 21:30 ` Al Viro
2021-08-30 22:00 ` Linus Torvalds
2021-08-30 22:12 ` Thomas Gleixner
2021-08-30 22:26 ` Linus Torvalds
2021-08-31 0:06 ` Al Viro
2021-08-31 0:34 ` Thomas Gleixner
2021-08-31 7:39 ` Borislav Petkov
2021-08-31 18:39 ` Luck, Tony
2021-09-01 7:27 ` Borislav Petkov
2021-08-30 22:01 ` Thomas Gleixner
2021-08-30 22:11 ` Linus Torvalds
2021-09-01 12:00 ` Thomas Gleixner
2021-09-01 15:52 ` Thomas Gleixner
2021-09-01 16:47 ` Sean Christopherson
2021-09-01 19:22 ` Thomas Gleixner
2021-09-01 19:22 ` Dave Hansen
2021-09-02 13:08 ` Jarkko Sakkinen [this message]
2021-09-02 14:08 ` Thomas Gleixner
2021-09-03 6:00 ` Jarkko Sakkinen
2021-09-03 6:05 ` Jarkko Sakkinen
2021-08-30 16:27 ` [patch 02/10] x86/fpu/signal: Move header zeroing out of xsave_to_user_sigframe() Thomas Gleixner
2021-08-30 16:27 ` [patch 03/10] x86/fpu/signal: Move xstate clearing out of copy_fpregs_to_sigframe() Thomas Gleixner
2021-08-30 16:27 ` [patch 04/10] x86/fpu/signal: Change return type of copy_fpstate_to_sigframe() to boolean Thomas Gleixner
2021-08-30 16:27 ` [patch 05/10] x86/fpu/signal: Change return type of copy_fpregs_to_sigframe() helpers " Thomas Gleixner
2021-08-30 16:27 ` [patch 06/10] x86/signal: Change return type of restore_sigcontext() " Thomas Gleixner
2021-08-30 16:27 ` [patch 07/10] x86/fpu/signal: Change return type of fpu__restore_sig() " Thomas Gleixner
2021-08-30 16:27 ` [patch 08/10] x86/fpu/signal: Change return type of __fpu_restore_sig() " Thomas Gleixner
2021-08-30 16:27 ` [patch 09/10] x86/fpu/signal: Change return code of check_xstate_in_sigframe() " Thomas Gleixner
2021-08-30 16:27 ` [patch 10/10] x86/fpu/signal: Change return code of restore_fpregs_from_user() " Thomas Gleixner
2021-08-30 17:39 ` [patch 00/10] x86/fpu: Clean up error handling in sigframe related code Linus Torvalds
2021-08-30 18:51 ` Thomas Gleixner
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