From: Peter Zijlstra <peterz@infradead.org>
To: Sean Christopherson <seanjc@google.com>
Cc: mingo@redhat.com, tglx@linutronix.de, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, linux-api@vger.kernel.org, x86@kernel.org,
pjt@google.com, posk@google.com, avagin@google.com,
jannh@google.com, tdelisle@uwaterloo.ca, mark.rutland@arm.com,
posk@posk.io
Subject: Re: [RFC][PATCH v2 4/5] x86/uaccess: Implement unsafe_try_cmpxchg_user()
Date: Thu, 27 Jan 2022 10:56:05 +0100 [thread overview]
Message-ID: <YfJsNcYNH8JTHrM/@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YfI9Y5l0fQAKuJav@google.com>
On Thu, Jan 27, 2022 at 06:36:19AM +0000, Sean Christopherson wrote:
> On Thu, Jan 27, 2022, Sean Christopherson wrote:
> > Doh, I should have specified that KVM needs 8-byte CMPXCHG on 32-bit kernels due
> > to using it to atomically update guest PAE PTEs and LTR descriptors (yay).
> >
> > Also, KVM's use case isn't a tight loop, how gross would it be to add a slightly
> > less unsafe version that does __uaccess_begin_nospec()? KVM pre-checks the address
> > way ahead of time, so the access_ok() check can be omitted. Alternatively, KVM
> > could add its own macro, but that seems a little silly. E.g. somethign like this,
> > though I don't think this is correct
>
> *sigh*
>
> Finally realized I forgot to add back the page offset after converting from guest
> page frame to host virtual address. Anyways, this is what I ended up with, will
> test more tomorrow.
Looks about right :-) (famous last words etc..)
next prev parent reply other threads:[~2022-01-27 9:56 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-20 15:55 [RFC][PATCH v2 0/5] sched: User Managed Concurrency Groups Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 1/5] mm: Avoid unmapping pinned pages Peter Zijlstra
2022-01-20 18:03 ` Nadav Amit
2022-01-21 7:59 ` Peter Zijlstra
2022-01-20 18:25 ` David Hildenbrand
2022-01-21 7:51 ` Peter Zijlstra
2022-01-21 8:22 ` David Hildenbrand
2022-01-21 8:59 ` Peter Zijlstra
2022-01-21 9:04 ` David Hildenbrand
2022-01-21 11:40 ` Peter Zijlstra
2022-01-21 12:04 ` David Hildenbrand
2022-01-20 15:55 ` [RFC][PATCH v2 2/5] entry,x86: Create common IRQ operations for exceptions Peter Zijlstra
2022-01-21 16:34 ` Mark Rutland
2022-01-20 15:55 ` [RFC][PATCH v2 3/5] sched/umcg: add WF_CURRENT_CPU and externise ttwu Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 4/5] x86/uaccess: Implement unsafe_try_cmpxchg_user() Peter Zijlstra
2022-01-27 2:17 ` Sean Christopherson
2022-01-27 6:36 ` Sean Christopherson
2022-01-27 9:56 ` Peter Zijlstra [this message]
2022-01-27 23:33 ` Sean Christopherson
2022-01-28 0:17 ` Nick Desaulniers
2022-01-28 16:29 ` Sean Christopherson
2022-01-27 9:55 ` Peter Zijlstra
2022-01-20 15:55 ` [RFC][PATCH v2 5/5] sched: User Mode Concurency Groups Peter Zijlstra
2022-01-21 11:47 ` Peter Zijlstra
2022-01-21 15:18 ` Peter Zijlstra
2022-01-24 14:29 ` Peter Zijlstra
2022-01-24 16:44 ` Peter Zijlstra
2022-01-24 17:06 ` Peter Oskolkov
2022-01-25 14:59 ` Peter Zijlstra
2022-01-24 13:59 ` Peter Zijlstra
2022-01-21 12:26 ` Peter Zijlstra
2022-01-21 16:57 ` Mark Rutland
2022-01-24 9:48 ` Peter Zijlstra
2022-01-24 10:03 ` Peter Zijlstra
2022-01-24 10:07 ` Peter Zijlstra
2022-01-24 10:27 ` Mark Rutland
2022-01-24 14:46 ` Tao Zhou
2022-01-27 12:19 ` Peter Zijlstra
2022-01-27 18:33 ` Tao Zhou
2022-01-27 12:25 ` Peter Zijlstra
2022-01-27 18:47 ` Tao Zhou
2022-01-27 12:26 ` Peter Zijlstra
2022-01-27 18:31 ` Tao Zhou
2022-01-20 17:28 ` [RFC][PATCH v2 0/5] sched: User Managed Concurrency Groups Peter Oskolkov
2022-01-21 8:01 ` Peter Zijlstra
2022-01-21 18:01 ` Steven Rostedt
2022-01-24 8:20 ` Peter Zijlstra
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