[PATCH] KVM: RISC-V: Avoid spurious virtual interrupts after clearing hideleg CSR

[Vincent Chen]

On Thu, Dec 23, 2021 at 8:34 PM Anup Patel <anup at brainfault.org> wrote:
>
> On Thu, Dec 23, 2021 at 8:43 AM Vincent Chen <vincent.chen at sifive.com> wrote:
> >
> > When the last VM is terminated, the host kernel will invoke function
> > hardware_disable_nolock() on each CPU to disable the related virtualization
> > functions. Here, RISC-V currently only clears hideleg CSR and hedeleg CSR.
> > This behavior will cause the host kernel to receive spurious interrupts if
> > hvip CSR has pending interrupts and the corresponding enable bits in vsie
> > CSR are asserted. To avoid it, hvip CSR and vsie CSR shall be cleared
> > earlier than hideleg CSR.
>
> Small correction in last sentence:
> ".... must be cleared before clearing hideleg CSR."
>
OK
> >
> > Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
> > ---
> >  arch/riscv/kvm/main.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/arch/riscv/kvm/main.c b/arch/riscv/kvm/main.c
> > index 421ecf4e6360..31777d29e864 100644
> > --- a/arch/riscv/kvm/main.c
> > +++ b/arch/riscv/kvm/main.c
> > @@ -58,6 +58,14 @@ int kvm_arch_hardware_enable(void)
> >
> >  void kvm_arch_hardware_disable(void)
> >  {
> > +       /*
> > +        * After clearing the hideleg CSR, the host kernel will receive spurious
> > +        * interrupts if hvip CSR has pending interrupts and the corresponding
> > +        * enable bits in vsie CSR are asserted. To avoid it, hvip CSR and
> > +        * vsie CSR shall be cleared early than hideleg CSR.
> > +        */
>
> Same correction as above.
OK

>
> > +       csr_write(CSR_VSIE, 0);
> > +       csr_write(CSR_HVIP, 0);
> >         csr_write(CSR_HEDELEG, 0);
> >         csr_write(CSR_HIDELEG, 0);
> >  }
> > --
> > 2.17.1
> >
> >
> > --
> > kvm-riscv mailing list
> > kvm-riscv at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/kvm-riscv
>
> Overall, this is a good fix but it is late in the development
> cycle so please add the "Fixes:" tag and also CC stable.
>

OK, I will add the "Fixes:" tag and also CC stable in my next version patch.
Thank you


> Reviewed-by: Anup Patel <anup.patel at wdc.com>
>
> Regards,
> Anup