Re: [PATCH v2 09/35] entry/kvm: handle lazy rescheduling at guest-entry

Peter Zijlstra
2024-05-28T16:13:23Z

On Mon, May 27, 2024 at 05:34:55PM -0700, Ankur Arora wrote:
> Archs defining CONFIG_KVM_XFER_TO_GUEST_WORK call
> xfer_to_guest_mode_handle_work() from various KVM vcpu-run
> loops to check for any task work including rescheduling.
>
> Handle TIF_NEED_RESCHED_LAZY alongside TIF_NEED_RESCHED.
>
> Also, while at it, remove the explicit check for need_resched() in
> the exit condition as that is already covered in the loop condition.
>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Andy Lutomirski <luto@kernel.org>
> Originally-by: Thomas Gleixner <tglx@linutronix.de>
> Link: https://lore.kernel.org/lkml/87jzshhexi.ffs@tglx/
> Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
> ---
> include/linux/entry-kvm.h | 2 +-
> kernel/entry/kvm.c | 4 ++--
> 2 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/entry-kvm.h b/include/linux/entry-kvm.h
> index 6813171afccb..674a622c91be 100644
> --- a/include/linux/entry-kvm.h
> +++ b/include/linux/entry-kvm.h
> @@ -18,7 +18,7 @@
>
> #define XFER_TO_GUEST_MODE_WORK \
> (_TIF_NEED_RESCHED | _TIF_SIGPENDING | _TIF_NOTIFY_SIGNAL | \
> - _TIF_NOTIFY_RESUME | ARCH_XFER_TO_GUEST_MODE_WORK)
> + _TIF_NOTIFY_RESUME | _TIF_NEED_RESCHED_LAZY | ARCH_XFER_TO_GUEST_MODE_WORK)

Same as last patch, it seems weird to have both RESCHED flags so far
apart.