From: Andy Lutomirski <luto@amacapital.net>
To: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
Andrew Lutomirski <luto@kernel.org>,
LKML <linux-kernel@vger.kernel.org>, X86 ML <x86@kernel.org>,
Radim Krcmar <rkrcmar@redhat.com>, kvm list <kvm@vger.kernel.org>,
"Jason A. Donenfeld" <Jason@zx2c4.com>,
Rik van Riel <riel@surriel.com>
Subject: Re: [PATCH 05/11] x86/fpu: set PKRU state for kernel threads
Date: Fri, 19 Oct 2018 10:37:16 -0700 [thread overview]
Message-ID: <4CCD6641-4CCC-485A-BDD9-50751C4139B0@amacapital.net> (raw)
In-Reply-To: <9c5ed364-4282-7dd3-f614-4e62632d81aa@linux.intel.com>
> On Oct 19, 2018, at 10:01 AM, Dave Hansen <dave.hansen@linux.intel.com> wrote:
>
> On 10/19/2018 09:59 AM, Andy Lutomirski wrote:
>>> That looks like a good API in general. The ffs_user_copy_worker that
>>> Sebastian mentioned seems to be used by AIO, in which case of course it
>>> has to happen in a kernel thread.
>>>
>>> But while the API is good, deciding on the desired semantics is
>>> "interesting". The submitting thread might be changing PKRU between the
>>> time the I/O operation is submitted and the time it is completed, for
>>> example.
>> I think there’s only one sensible answer: capture PKRU at the time of submission.
>
> I think it's much more straightforward to just not enforce pkeys.
> Having this "phantom" value could cause a very odd, nearly undebuggable
> I/O failure.
But now we have the reverse. The IO can work if it’s truly async but, if the kernel decides to synchronously complete IO (with GUP or copy_to_user), it’ll fail, right. This isn’t exactly friendly either.
next prev parent reply other threads:[~2018-10-19 17:37 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-04 14:05 [PATCH 00/11 v3] x86: load FPU registers on return to userland Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 01/11] x86/entry: remove _TIF_ALLWORK_MASK Sebastian Andrzej Siewior
2018-10-11 16:27 ` Borislav Petkov
2018-10-04 14:05 ` [PATCH 02/11] x86/fpu: add (__)make_fpregs_active helpers Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 03/11] x86/fpu: make __raw_xsave_addr() use feature number instead of mask Sebastian Andrzej Siewior
2018-10-11 17:30 ` Christophe de Dinechin
2018-10-18 11:19 ` Sebastian Andrzej Siewior
2018-10-12 15:52 ` Dave Hansen
2018-10-18 11:17 ` Sebastian Andrzej Siewior
2018-10-18 11:21 ` Sebastian Andrzej Siewior
2018-10-17 10:01 ` Borislav Petkov
2018-10-18 11:48 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 04/11] x86/fpu: eager switch PKRU state Sebastian Andrzej Siewior
2018-10-12 17:51 ` Dave Hansen
2018-10-12 18:09 ` Andy Lutomirski
2018-10-12 19:44 ` Dave Hansen
2018-10-18 16:13 ` Sebastian Andrzej Siewior
2018-10-18 17:50 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 05/11] x86/fpu: set PKRU state for kernel threads Sebastian Andrzej Siewior
2018-10-12 17:54 ` Dave Hansen
2018-10-12 18:02 ` Andy Lutomirski
2018-10-18 16:26 ` Sebastian Andrzej Siewior
2018-10-18 16:48 ` Andy Lutomirski
2018-10-18 17:47 ` Dave Hansen
2018-10-18 18:25 ` Sebastian Andrzej Siewior
2018-10-18 20:46 ` Andy Lutomirski
2018-10-18 20:56 ` Dave Hansen
2018-10-18 21:24 ` Sebastian Andrzej Siewior
2018-10-18 21:58 ` Andy Lutomirski
2018-10-19 7:44 ` Paolo Bonzini
2018-10-19 16:59 ` Andy Lutomirski
2018-10-19 17:01 ` Dave Hansen
2018-10-19 17:37 ` Andy Lutomirski [this message]
2018-10-19 18:26 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 06/11] x86/pkeys: make init_pkru_value static Sebastian Andrzej Siewior
2018-10-12 17:55 ` Dave Hansen
2018-10-04 14:05 ` [PATCH 07/11] x86/pkeys: Drop the preempt-disable section Sebastian Andrzej Siewior
2018-10-12 17:58 ` Dave Hansen
2018-10-12 18:07 ` Andy Lutomirski
2018-10-12 20:26 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 08/11] x86/fpu: Always store the registers in copy_fpstate_to_sigframe() Sebastian Andrzej Siewior
2018-10-11 17:50 ` Christophe de Dinechin
2018-10-11 21:18 ` Andy Lutomirski
2018-10-12 18:15 ` Dave Hansen
2018-11-02 14:42 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 09/11] x86/entry: add TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 10/11] x86/fpu: prepare copy_fpstate_to_sigframe for TIF_LOAD_FPU Sebastian Andrzej Siewior
2018-10-12 19:40 ` Dave Hansen
2018-10-15 15:24 ` Borislav Petkov
2018-11-02 15:44 ` Sebastian Andrzej Siewior
2018-11-02 22:55 ` Sebastian Andrzej Siewior
2018-10-04 14:05 ` [PATCH 11/11] x86/fpu: defer FPU state load until return to userspace Sebastian Andrzej Siewior
2018-10-04 16:14 ` Andy Lutomirski
2018-10-12 20:25 ` Sebastian Andrzej Siewior
2018-10-04 16:45 ` [PATCH 00/11 v3] x86: load FPU registers on return to userland Rik van Riel
2018-10-04 16:50 ` Andy Lutomirski
2018-10-05 11:55 ` Sebastian Andrzej Siewior
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