From: Linus Torvalds <torvalds@linux-foundation.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: Pavel Machek <pavel@ucw.cz>, Zhang Rui <rui.zhang@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
Jarkko Nikula <jarkko.nikula@linux.intel.com>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"the arch/x86 maintainers" <x86@kernel.org>
Subject: Re: Linux 4.15-rc2: Regression in resume from ACPI S3
Date: Tue, 12 Dec 2017 10:36:43 -0800 [thread overview]
Message-ID: <CA+55aFxSZX0FWKzxbcAsTz5huk9ftHkHmfnuhckjuVs4byETgQ@mail.gmail.com> (raw)
In-Reply-To: <CALCETrVBZrL-SBpSw5zzTZb36Dr72AjxfO7Dq5Onz7K8GZt4AA@mail.gmail.com>
On Tue, Dec 12, 2017 at 10:05 AM, Andy Lutomirski <luto@kernel.org> wrote:
>>
>> - do NOT use "load_gs_index()", which does that swapgs dance (twice!)
>> and plays with interrupt state. Just load the segment register, and
>> then do the wrmsrl() of the {FS,GS,KERNEL_GS}_BASE values. There is no
>> need for the swapgs dance.
>
> Using what helper? On x86_64, it can fault, and IIRC we explicitly
> don't allow loadsegment(gs, ...).
Just do the loadsegment() thing. The fact that we don't have a gs
version of it is legacy - to catch bad users. It shouldn't stop us
from having good users.
That said - can it really fault? Because if it can, then why can't %fs
fault? And on x86-64, we just do
asm volatile ("movw %0, %%fs" :: "r" (ctxt->fs));
and don't actually use 'loadsegment()' for _any_ of the segments. We
only do the fault protection on 32-bit.
In fact, we really should try to avoid taking faults here anyway,
shouldn't we? We haven't loaded enough of the context yet.
Hmm.
Maybe we should load only the fixed kernel segments at this point, and
then do all the loadsegment() of gs/fs in the later phase when we're
all set up.
THERE we can do the swapgs dance with interrupt tracing etc, because
*there* we actually are fully set up. I guess that means reloading the
FS/GS base MSR's,
Linus
next prev parent reply other threads:[~2017-12-12 18:36 UTC|newest]
Thread overview: 83+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-12-03 16:22 Linux 4.15-rc2 Linus Torvalds
2017-12-04 22:25 ` Linux 4.15-rc2: Regression in resume from ACPI S3 Rafael J. Wysocki
2017-12-04 22:36 ` Linus Torvalds
2017-12-04 22:38 ` Thomas Gleixner
2017-12-04 22:41 ` Rafael J. Wysocki
2017-12-05 0:25 ` Rafael J. Wysocki
2017-12-09 10:33 ` Pavel Machek
2017-12-09 11:41 ` Pavel Machek
[not found] ` <CA+55aFw8tuoJ2gcXx3K2sKFf2Y9hXX4naMVQNqGOUivnjwhjkg@mail.gmail.com>
2017-12-09 22:01 ` Pavel Machek
[not found] ` <CA+55aFySAdiBZhZ0PSDjH5PuvPPcMsBRXbxCkObfm1eY7gHDbQ@mail.gmail.com>
2017-12-10 16:23 ` Pavel Machek
2017-12-10 16:37 ` Linus Torvalds
2017-12-10 18:56 ` Pavel Machek
2017-12-10 20:30 ` Linus Torvalds
2017-12-10 20:43 ` Pavel Machek
2017-12-10 21:28 ` Linus Torvalds
2017-12-10 21:35 ` Pavel Machek
2017-12-12 17:27 ` Linus Torvalds
2017-12-12 18:05 ` Andy Lutomirski
2017-12-12 18:36 ` Linus Torvalds [this message]
2017-12-12 22:10 ` Andy Lutomirski
2017-12-12 22:33 ` Linus Torvalds
2017-12-12 23:10 ` Andy Lutomirski
2017-12-13 11:16 ` Jarkko Nikula
2017-12-13 12:40 ` Ingo Molnar
2017-12-13 18:50 ` Andy Lutomirski
2017-12-10 21:38 ` [PATCH] Fix resume on x86-32 machines Pavel Machek
2017-12-10 21:58 ` Andy Lutomirski
2017-12-10 22:20 ` Pavel Machek
2017-12-11 9:25 ` Jarkko Nikula
2017-12-11 14:22 ` Rafael J. Wysocki
2017-12-11 14:43 ` Rafael J. Wysocki
2017-12-11 14:59 ` Jarkko Nikula
2017-12-11 18:31 ` Linus Torvalds
2017-12-11 18:41 ` Andy Lutomirski
2017-12-11 19:12 ` Linus Torvalds
2017-12-14 20:38 ` Pavel Machek
2017-12-14 20:47 ` Linus Torvalds
2017-12-14 21:20 ` Andy Lutomirski
2017-12-14 22:22 ` Pavel Machek
2017-12-11 15:13 ` Ingo Molnar
2017-12-11 16:26 ` Andy Lutomirski
2017-12-11 14:09 ` Linux 4.15-rc2: Regression in resume from ACPI S3 Zhang Rui
2017-12-11 16:28 ` Andy Lutomirski
2017-12-12 8:00 ` Pavel Machek
2017-12-06 12:15 ` Michal Hocko
2017-12-06 12:23 ` Thomas Gleixner
2017-12-06 14:04 ` Rafael J. Wysocki
2017-12-06 12:31 ` Maarten Lankhorst
2017-12-06 12:46 ` Thomas Gleixner
2017-12-06 13:09 ` Maarten Lankhorst
2017-12-06 14:15 ` Thomas Gleixner
2017-12-07 13:33 ` Maarten Lankhorst
2017-12-08 10:30 ` Thomas Gleixner
2017-12-13 15:57 ` Thomas Gleixner
2017-12-13 16:23 ` Bjorn Helgaas
2017-12-13 16:41 ` Thomas Gleixner
2017-12-13 17:45 ` Linus Torvalds
2017-12-13 18:19 ` Thomas Gleixner
2017-12-13 20:52 ` Thomas Gleixner
2017-12-13 21:06 ` Thomas Gleixner
2017-12-13 22:48 ` Rafael J. Wysocki
2017-12-14 11:54 ` Thomas Gleixner
2017-12-14 12:12 ` Rafael J. Wysocki
2017-12-14 12:30 ` Thomas Gleixner
2017-12-14 15:30 ` Rafael J. Wysocki
2017-12-14 15:52 ` Thomas Gleixner
2017-12-14 15:54 ` Rafael J. Wysocki
2017-12-14 16:17 ` Maarten Lankhorst
2017-12-15 2:07 ` [PATCH] PCI / PM: Force devices to D0 in pci_pm_thaw_noirq() Rafael J. Wysocki
2017-12-15 14:28 ` Rafael J. Wysocki
2017-12-15 18:30 ` Bjorn Helgaas
2017-12-15 23:44 ` Rafael J. Wysocki
2017-12-14 13:24 ` Linux 4.15-rc2: Regression in resume from ACPI S3 Thomas Gleixner
2017-12-14 19:03 ` Linus Torvalds
2017-12-14 22:36 ` Thomas Gleixner
2017-12-14 22:47 ` Linus Torvalds
2017-12-15 9:05 ` Thomas Gleixner
2017-12-15 0:34 ` Rafael J. Wysocki
2017-12-13 22:39 ` Rafael J. Wysocki
2017-12-13 23:26 ` Rafael J. Wysocki
2017-12-07 7:55 ` Michal Hocko
2017-12-10 20:30 ` Michal Hocko
2018-02-21 18:36 ` Linux 4.15-rc2 Eugene Syromiatnikov
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