From: Paolo Bonzini <pbonzini@redhat.com>
To: Andy Lutomirski <luto@amacapital.net>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Andrew Lutomirski <luto@kernel.org>,
Dave Hansen <dave.hansen@linux.intel.com>,
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 09:44:18 +0200 [thread overview]
Message-ID: <2fe82232-4e80-8317-757c-d2235c4633d8@redhat.com> (raw)
In-Reply-To: <CALCETrVjEOkNhdyAF10PaYi_rnFUWKRqPhLRCq3ZV=gxQFETxg@mail.gmail.com>
On 18/10/2018 22:46, Andy Lutomirski wrote:
>> [0] drivers/usb/gadget/function/f_fs.c::ffs_user_copy_worker()
>>
>> Sebastian
> I think we need an entirely new API:
>
> user_mm_ctx_t ctx = user_mm_ctx_get();
>
> ...
>
> use_user_mm_ctx(ctx);
> unuse_user_mm_ctx(ctx);
>
> ...
>
> user_mm_ctx_put(ctx);
>
> and ctx will store a copy of mm and PKRU.
>
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. You could look up the task's PKRU at use_mm time, except that
the task might have disappeared... In the end just using PKRU=0 makes
some sense and it only should be documented that some kernel services
will ignore PKRU.
Paolo
next prev parent reply other threads:[~2018-10-19 7:44 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 [this message]
2018-10-19 16:59 ` Andy Lutomirski
2018-10-19 17:01 ` Dave Hansen
2018-10-19 17:37 ` Andy Lutomirski
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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