lkml.org 
[lkml]   [2017]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH v2 6/8] x86/entry: add unwind hint annotations
On Fri, Jun 30, 2017 at 6:11 AM, Josh Poimboeuf <jpoimboe@redhat.com> wrote:
> On Thu, Jun 29, 2017 at 10:41:44PM -0700, Andy Lutomirski wrote:
>> On Thu, Jun 29, 2017 at 10:05 PM, Andy Lutomirski <luto@kernel.org> wrote:
>> > Hmm. There's another option that might be considerably nicer, though:
>> > put the IRQ stack at a known (at link time) position *in percpu
>> > space*. (Presumably it already is -- I haven't checked.) Then we do:
>> >
>> > .macro ENTER_IRQ_STACK old_rsp
>> > DEBUG_ENTRY_ASSERT_IRQS_OFF
>> > movq %rsp, \old_rsp
>> > incl PER_CPU_VAR(irq_count)
>> >
>> > /*
>> > * Right now, if we just incremented irq_count to zero, we've
>> > * claimed the IRQ stack but we haven't switched to it yet.
>> > * Anything that can interrupt us here without using IST
>> > * must be *extremely* careful to limit its stack usage.
>> > */
>> > jnz .Lpush_old_rsp_\@
>> > movq \old_rsp, PER_CPU_VAR(top_word_in_irq_stack)
>> > movq PER_CPU_VAR(irq_stack_ptr), %rsp
>> > .Lpush_old_rsp_\@:
>> > pushq \old_rsp
>> > .endm
>> >
>>
>> How about the two commits here (well, soon to be there once gitweb catches up):
>>
>> https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=0f56a55bb133cd53ccb78ca51378086296618322
>>
>> If you like them, want to add them to your series?
>
> The second patch looks good to me, thanks. I can pick up the patches.
>
> A few comments about the first patch:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/entry_irq_stack&id=3e2aa2102cc1c5e60d4a8637bff78d0478a55059
>
> - It uses a '693:' label instead of '.Lirqs_off_\@:'

Touché!

>
> - There's a comment I don't follow:
>
> "Anything that can interrupt us here without using IST must be
> *extremely* careful to limit its stack usage."
>
> What specifically could interrupt there without using IST?

#DB, later on in the series. I'll update the comment.

>
> - Since do_softirq_own_stack() is a callable function, I think it still
> needs to save rbp.

Whoops.

>
> - Why change the "jmp error_exit" to "ret" in
> xen_do_hypervisor_callback()?

To match the other change I made there. I removed both.

\
 
 \ /
  Last update: 2017-06-30 23:14    [W:0.094 / U:2.148 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site