Re: [PATCH v2 03/15] KVM: arm64: nv: Handle CPACR_EL1 traps

Oliver Upton
2024-06-14T20:06:50Z

On Fri, Jun 14, 2024 at 02:20:54PM +0100, Marc Zyngier wrote:
> On Thu, 13 Jun 2024 21:17:44 +0100,
> Oliver Upton <oliver.upton@linux.dev> wrote:
> >
> > From: Marc Zyngier <maz@kernel.org>
> >
> > Handle CPACR_EL1 accesses when running a VHE guest. In order to
> > limit the cost of the emulation, implement it ass a shallow exit.
> >
> > In the other cases:
> >
> > - this is a nVHE L1 which will write to memory, and we don't trap
> >
> > - this is a L2 guest:
> >
> > * the L1 has CPTR_EL2.TCPAC==0, and the L2 has direct register
> > access
> >
> > * the L1 has CPTR_EL2.TCPAC==1, and the L2 will trap, but the
> > handling is defered to the general handling for forwarding
> >
> > Signed-off-by: Marc Zyngier <maz@kernel.org>
> > Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
> > ---
> > arch/arm64/kvm/hyp/vhe/switch.c | 32 +++++++++++++++++++++++++++++++-
> > 1 file changed, 31 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/vhe/switch.c b/arch/arm64/kvm/hyp/vhe/switch.c
> > index d7af5f46f22a..fed36457fef9 100644
> > --- a/arch/arm64/kvm/hyp/vhe/switch.c
> > +++ b/arch/arm64/kvm/hyp/vhe/switch.c
> > @@ -262,10 +262,40 @@ static bool kvm_hyp_handle_eret(struct kvm_vcpu *vcpu, u64 *exit_code)
> > return true;
> > }
> >
> > +static bool kvm_hyp_handle_cpacr_el1(struct kvm_vcpu *vcpu, u64 *exit_code)
> > +{
> > + u64 esr = kvm_vcpu_get_esr(vcpu);
> > + int rt;
> > +
> > + if (!is_hyp_ctxt(vcpu) || esr_sys64_to_sysreg(esr) != SYS_CPACR_EL1)
> > + return false;
> > +
> > + rt = kvm_vcpu_sys_get_rt(vcpu);
> > +
> > + if ((esr & ESR_ELx_SYS64_ISS_DIR_MASK) == ESR_ELx_SYS64_ISS_DIR_READ) {
> > + vcpu_set_reg(vcpu, rt, __vcpu_sys_reg(vcpu, CPTR_EL2));
> > + } else {
> > + vcpu_write_sys_reg(vcpu, vcpu_get_reg(vcpu, rt), CPTR_EL2);
> > + __activate_cptr_traps(vcpu);
>
> This doesn't bisect, as this helper is only introduced in patch #10.
> You probably want to keep it towards the end of the series.

Ah, derp, I wanted to use the kvm_hyp_handle_sysreg_vhe() you introduced
for the subsequent patch. I'll just move them both.

--
Thanks,
Oliver