lkml.org 
[lkml]   [2017]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH 1/2] x86,kvm: move qemu/guest FPU switching out to vcpu_run
    From
    Date
    On 16/11/2017 14:35, Quan Xu wrote:
    > but we introduce another method:
    >
    >       -- When the VCPU thread is scheduled back in, the context
    >          switch code will restore current->thread.fpu to the FPU
    >          registers.
    >
    >
    > there is still a window to restore current->thread.fpu to the FPU
    > registers before enter guest mode and
    >
    > preempt_disable().

    That will always use the host PKRU. The guest PKRU is _never_ visible
    to the context switch code, because it's only ever used in a section
    that runs with preemption disabled.

    It's actually much simpler than before.

    Paolo

    > on target machine, after migration, the pkru value is source_host_pkru
    > in current->thread.fpu.
    >
    > in case,
    >
    >             source_host_pkru_value != guest_pkru_value,
    >             target_host_pkru_value == guest_pkru_value..
    >
    > source_host_pkru_value may be restored to PKRU.. make pkru status
    > inconsistent..

    \
     
     \ /
      Last update: 2017-11-17 17:17    [W:2.571 / U:0.260 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site