From: "Jürgen Groß" <jgross@suse.com>
To: Peter Zijlstra <peterz@infradead.org>, Marco Elver <elver@google.com>
Cc: syzbot <syzbot+8db9e1ecde74e590a657@syzkaller.appspotmail.com>,
fenghua.yu@intel.com, yu-cheng.yu@intel.com, "Luck,
Tony" <tony.luck@intel.com>,
"Paul E. McKenney" <paulmck@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
LKML <linux-kernel@vger.kernel.org>,
kasan-dev <kasan-dev@googlegroups.com>,
virtualization@lists.linux-foundation.org,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Wei Liu <wei.liu@kernel.org>,
the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH] x86/paravirt: Add missing noinstr to arch_local*() helpers
Date: Tue, 11 Aug 2020 09:57:55 +0200 [thread overview]
Message-ID: <a2dffeeb-04f0-8042-b39a-b839c4800d6f@suse.com> (raw)
In-Reply-To: <20200811074127.GR3982@worktop.programming.kicks-ass.net>
On 11.08.20 09:41, Peter Zijlstra wrote:
> On Fri, Aug 07, 2020 at 05:19:03PM +0200, Marco Elver wrote:
>
>> My hypothesis here is simply that kvm_wait() may be called in a place
>> where we get the same case I mentioned to Peter,
>>
>> raw_local_irq_save(); /* or other IRQs off without tracing */
>> ...
>> kvm_wait() /* IRQ state tracing gets confused */
>> ...
>> raw_local_irq_restore();
>>
>> and therefore, using raw variants in kvm_wait() works. It's also safe
>> because it doesn't call any other libraries that would result in corrupt
>
> Yes, this is definitely an issue.
>
> Tracing, we also musn't call into tracing when using raw_local_irq_*().
> Because then we re-intoduce this same issue all over again.
>
> Both halt() and safe_halt() are more paravirt calls, but given we're in
> a KVM paravirt call already, I suppose we can directly use native_*()
> here.
>
> Something like so then... I suppose, but then the Xen variants need TLC
> too.
Just to be sure I understand you correct:
You mean that xen_qlock_kick() and xen_qlock_wait() and all functions
called by those should gain the "notrace" attribute, right?
I am not sure why the kick variants need it, though. IMO those are
called only after the lock has been released, so they should be fine
without notrace.
And again: we shouldn't forget the Hyper-V variants.
Juergen
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next prev parent reply other threads:[~2020-08-11 7:58 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <0000000000007d3b2d05ac1c303e@google.com>
[not found] ` <20200805132629.GA87338@elver.google.com>
2020-08-05 13:42 ` [PATCH] x86/paravirt: Add missing noinstr to arch_local*() helpers peterz
[not found] ` <20200805135940.GA156343@elver.google.com>
2020-08-05 14:12 ` peterz
2020-08-05 14:17 ` Jürgen Groß
2020-08-05 14:17 ` peterz
[not found] ` <CANpmjNN6FWZ+MsAn3Pj+WEez97diHzqF8hjONtHG15C2gSpSgw@mail.gmail.com>
[not found] ` <CANpmjNNy3XKQqgrjGPPKKvXhAoF=mae7dk8hmoS4k4oNnnB=KA@mail.gmail.com>
[not found] ` <20200806074723.GA2364872@elver.google.com>
2020-08-06 11:32 ` peterz
[not found] ` <20200806131702.GA3029162@elver.google.com>
[not found] ` <CANpmjNNqt8YrCad4WqgCoXvH47pRXtSLpnTKhD8W8+UpoYJ+jQ@mail.gmail.com>
[not found] ` <CANpmjNO860SHpNve+vaoAOgarU1SWy8o--tUWCqNhn82OLCiew@mail.gmail.com>
2020-08-07 9:24 ` Jürgen Groß
[not found] ` <20200807095032.GA3528289@elver.google.com>
2020-08-07 10:35 ` Jürgen Groß
[not found] ` <20200807113838.GA3547125@elver.google.com>
2020-08-07 12:04 ` Jürgen Groß
[not found] ` <CANpmjNPau_DEYadey9OL+iFZKEaUTqnFnyFs1dU12o00mg7ofA@mail.gmail.com>
[not found] ` <20200807151903.GA1263469@elver.google.com>
[not found] ` <CANpmjNM1jASqCFYZpteVrZCa2V2D_DbXaqvoCV_Ac2boYfDXnQ@mail.gmail.com>
2020-08-11 7:04 ` Jürgen Groß
2020-08-11 7:41 ` Peter Zijlstra
2020-08-11 7:57 ` Jürgen Groß [this message]
2020-08-11 8:12 ` Peter Zijlstra
2020-08-11 8:18 ` Jürgen Groß
2020-08-11 8:38 ` Jürgen Groß
2020-08-11 9:20 ` peterz
2020-08-11 9:46 ` peterz
2020-08-11 20:17 ` peterz
[not found] ` <20200812080650.GA3894595@elver.google.com>
2020-08-12 8:18 ` peterz
2020-08-12 8:57 ` peterz
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