[lkml]   [2020]   [Nov]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: WARNING: can't access registers at asm_common_interrupt

> On Nov 14, 2020, at 10:33 PM, Jürgen Groß <> wrote:
> On 14.11.20 19:10, Andy Lutomirski wrote:
>>> On Sat, Nov 14, 2020 at 1:16 AM Jürgen Groß <> wrote:
>>> On 13.11.20 18:34, Andy Lutomirski wrote:
>>>> On Wed, Nov 11, 2020 at 12:25 PM Andrew Cooper
>>>> <> wrote:
>>>> So I think there is at most one of these that wants anything more
>>>> complicated than a plain ALTERNATIVE. Any volunteers to make it so?
>>>> Juergen, if you do all of them except USERGS_SYSRET64, I hereby
>>>> volunteer to do that one.
>>> Why is a plain alternative (either swapgs; sysretq or a jmp xen_sysret64
>>> depending on X86_FEATURE_XENPV) no option?
>>> Its not as if this code would run before alternative patching.
>> ALTERNATIVE would "work" in the sense that it would function and be
>> just about as nonsensical as the current code. Fundamentally, Xen
>> PV's sysret feature is not a drop-in replacement for SYSRET64, and
>> pretending that it is seems unlikely to work well. I suspect that the
>> current code is some combination of exceedingly slow, non-functional,
>> and incorrect in subtle ways.
>> We should just have a separate Xen PV exit path the same way we have a
>> separate entry path in recent kernels. *This* is what I'm
>> volunteering to do.
> I don't think there is much work needed. Xen PV does basically a return
> to user mode via IRET. I think it might work just to use
> swapgs_restore_regs_and_return_to_usermode() unconditionally for Xen PV.

I’m quite confident that will work, but I was hoping to get it to work quickly too :)

> Juergen
> <OpenPGP_0xB0DE9DD628BF132F.asc>

 \ /
  Last update: 2020-11-15 17:06    [W:0.099 / U:0.012 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site