On Tue, Apr 04, 2017 at 02:39:19PM +0100, Marc Zyngier wrote:
> On 31/03/17 17:06, Andrew Jones wrote:
> > This not only ensures visibility of changes to pause by using
> > atomic ops, but also plugs a small race where a vcpu could get its
> > pause state enabled just after its last check before entering the
> > guest. With this patch, while the vcpu will still initially enter
> > the guest, it will exit immediately due to the IPI sent by the vcpu
> > kick issued after making the vcpu request.
> >
> > We use bitops, rather than kvm_make/check_request(), because we
> > don't need the barriers they provide, nor do we want the side-effect
> > of kvm_check_request() clearing the request. For pause, only the
> > requester should do the clearing.
> >
> > Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
> > ---
> > arch/arm/include/asm/kvm_host.h | 5 +----
> > arch/arm/kvm/arm.c | 45 +++++++++++++++++++++++++++------------
> > arch/arm64/include/asm/kvm_host.h | 5 +----
> > 3 files changed, 33 insertions(+), 22 deletions(-)
> >
> > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> > index 31ee468ce667..52c25536d254 100644
> > --- a/arch/arm/include/asm/kvm_host.h
> > +++ b/arch/arm/include/asm/kvm_host.h
> > @@ -45,7 +45,7 @@
> > #define KVM_MAX_VCPUS VGIC_V2_MAX_CPUS
> > #endif
> >
> > -#define KVM_REQ_VCPU_EXIT 8
> > +#define KVM_REQ_PAUSE 8
>
> Small nit: can we have a #define for this 8? KVM_REQ_ARCH_BASE, or
> something along those lines?
Sounds good to me. Should I even do something like
#define KVM_REQ_ARCH_BASE 8
#define KVM_ARCH_REQ(bit) ({ \
BUILD_BUG_ON(((bit) + KVM_REQ_ARCH_BASE) >= BITS_PER_LONG); \
((bit) + KVM_REQ_ARCH_BASE); \
})
#define KVM_REQ_PAUSE KVM_ARCH_REQ(0)
or would that be overkill? Also, whether we switch to just the base
define, or the macro, I guess it would be good to do for all
architectures.
Thanks,
drew
>
> I've otherwise started hammering this series over a number of systems,
> looking good so far.
>
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...
