Re: [PATCH] RISC-V: KVM: Exit run-loop immediately if xfer_to_guest fails
From: Anup Patel
Date: Sun Nov 27 2022 - 07:19:53 EST
On Tue, Nov 8, 2022 at 5:48 PM Andreas Schwab <schwab@xxxxxxx> wrote:
>
> On Nov 08 2022, Anup Patel wrote:
>
> > If xfer_to_guest_mode_handle_work() fails in the run-loop then exit
> > the run-loop immediately instead of doing it after some more work.
> >
> > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > Reviewed-by: Andrew Jones <ajones@xxxxxxxxxxxxxxxx>
> > ---
> > arch/riscv/kvm/vcpu.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > index 71ebbc4821f0..17d5b3f8c2ee 100644
> > --- a/arch/riscv/kvm/vcpu.c
> > +++ b/arch/riscv/kvm/vcpu.c
> > @@ -984,8 +984,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu)
> > while (ret > 0) {
> > /* Check conditions before entering the guest */
> > ret = xfer_to_guest_mode_handle_work(vcpu);
> > - if (!ret)
> > - ret = 1;
> > + if (ret)
> > + continue;
>
> If that is supposed to exit the loop, it would be clearer to just use
> break.
This is a convention within the run-loop that we continue whenever
whenever "ret" is no longer suitable to continue. I don't see any
particular advantage in breaking this convention over here.
>
> > + ret = 1;
>
> There is a condition on ret <= 0 later in the loop that no longer can be
> true.
Yes, for now the "ret <= 0" check is useless and the compiler will
optimize this comparison. We will be soon having more stuff added
to run-loop (such as AIA update) which will make "ret <= 0" check
useful again.
>
> --
> Andreas Schwab, SUSE Labs, schwab@xxxxxxx
> GPG Key fingerprint = 0196 BAD8 1CE9 1970 F4BE 1748 E4D4 88E3 0EEA B9D7
> "And now for something completely different."
Queued this patch for Linux-6.2
Thanks,
Anup