Re: [PATCH v7 21/27] KVM: arm/arm64: Add hook for arch-specific KVM initialisation

Andrew Jones
2019-04-04T16:33:20Z

On Thu, Apr 04, 2019 at 03:53:55PM +0100, Dave Martin wrote:
> On Thu, Apr 04, 2019 at 04:25:28PM +0200, Andrew Jones wrote:
> > On Fri, Mar 29, 2019 at 01:00:46PM +0000, Dave Martin wrote:
> > > This patch adds a kvm_arm_init_arch_resources() hook to perform
> > > subarch-specific initialisation when starting up KVM.
> > >
> > > This will be used in a subsequent patch for global SVE-related
> > > setup on arm64.
> > >
> > > No functional change.
> > >
> > > Signed-off-by: Dave Martin <Dave.Martin@arm.com>
> > > Reviewed-by: Julien Thierry <julien.thierry@arm.com>
> > > Tested-by: zhang.lei <zhang.lei@jp.fujitsu.com>
> > > ---
> > > arch/arm/include/asm/kvm_host.h | 2 ++
> > > arch/arm64/include/asm/kvm_host.h | 2 ++
> > > virt/kvm/arm/arm.c | 4 ++++
> > > 3 files changed, 8 insertions(+)
> > >
> > > diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> > > index 770d732..a49ee01 100644
> > > --- a/arch/arm/include/asm/kvm_host.h
> > > +++ b/arch/arm/include/asm/kvm_host.h
> > > @@ -53,6 +53,8 @@
> > >
> > > DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
> > >
> > > +static inline int kvm_arm_init_arch_resources(void) { return 0; }
> > > +
> > > u32 *kvm_vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num, u32 mode);
> > > int __attribute_const__ kvm_target_cpu(void);
> > > int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
> > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > > index 205438a..3e89509 100644
> > > --- a/arch/arm64/include/asm/kvm_host.h
> > > +++ b/arch/arm64/include/asm/kvm_host.h
> > > @@ -58,6 +58,8 @@
> > >
> > > DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
> > >
> > > +static inline int kvm_arm_init_arch_resources(void) { return 0; }
> > > +
> > > int __attribute_const__ kvm_target_cpu(void);
> > > int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
> > > int kvm_arch_vm_ioctl_check_extension(struct kvm *kvm, long ext);
> > > diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> > > index 99c3738..c69e137 100644
> > > --- a/virt/kvm/arm/arm.c
> > > +++ b/virt/kvm/arm/arm.c
> > > @@ -1664,6 +1664,10 @@ int kvm_arch_init(void *opaque)
> > > if (err)
> > > return err;
> > >
> > > + err = kvm_arm_init_arch_resources();
> > > + if (err)
> > > + return err;
> > > +
> > > if (!in_hyp_mode) {
> > > err = init_hyp_mode();
> > > if (err)
> > > --
> > > 2.1.4
> > >
> >
> > It's not clear to me from the commit message why init_common_resources()
> > won't work for this. Maybe it'll be more clear as I continue the review.
>
> init_common_resources() is for stuff common to arm and arm64.

Well currently init_common_resources() only calls kvm_set_ipa_limit(),
which isn't implemented for arm. So if there was a plan to only use
that function for init that actually does something on both, it doesn't.

>
> kvm_arm_init_arch_resources() is intended for stuff specific to the
> particular arch backend.

I'm not sure we need that yet. We just need an arm setup sve stub like
arm's kvm_set_ipa_limit() stub. OTOH, if we have to keep adding stubs
to arm we should probably have something like
kvm_arm_init_arch_resources() instead, and kvm_set_ipa_limit() should
be moved inside the arm64 one and the arm ipa limit stub can go. Then
since init_common_resources() would no longer be used, it could just
be deleted.

>
> Maybe there is a better name for this.
>

The name is fine for me.

Thanks,
drew