On Fri, 07 Jan 2022 21:54:01 +0000,
Chase Conklin <chase.conklin@xxxxxxx> wrote:
>
> Hi Marc,
>
> On Mon Nov 29 15:00:49 EST 2021, Marc Zyngier <maz@xxxxxxxxxx> wrote:
> > From: Christoffer Dall <christoffer.dall at arm.com>
> >
> > Reset the VCPU with PSTATE.M = EL2h when the nested virtualization
> > feature is enabled on the VCPU.
> >
> > Signed-off-by: Christoffer Dall <christoffer.dall at arm.com>
> > [maz: rework register reset not to use empty data structures]
> > Signed-off-by: Marc Zyngier <maz at kernel.org>
> > ---
> > arch/arm64/kvm/reset.c | 10 ++++++++--
> > 1 file changed, 8 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> > index 426bd7fbc3fd..38a7182819fb 100644
> > --- a/arch/arm64/kvm/reset.c
> > +++ b/arch/arm64/kvm/reset.c
> > @@ -27,6 +27,7 @@
> > #include <asm/kvm_asm.h>
> > #include <asm/kvm_emulate.h>
> > #include <asm/kvm_mmu.h>
> > +#include <asm/kvm_nested.h>
> > #include <asm/virt.h>
> >
> > /* Maximum phys_shift supported for any VM on this host */
> > @@ -38,6 +39,9 @@ static u32 kvm_ipa_limit;
> > #define VCPU_RESET_PSTATE_EL1 (PSR_MODE_EL1h | PSR_A_BIT | PSR_I_BIT | \
> > PSR_F_BIT | PSR_D_BIT)
> >
> > +#define VCPU_RESET_PSTATE_EL2 (PSR_MODE_EL2h | PSR_A_BIT | PSR_I_BIT | \
> > + PSR_F_BIT | PSR_D_BIT)
> > +
> > #define VCPU_RESET_PSTATE_SVC (PSR_AA32_MODE_SVC | PSR_AA32_A_BIT | \
> > PSR_AA32_I_BIT | PSR_AA32_F_BIT)
> >
> > @@ -176,8 +180,8 @@ static bool vcpu_allowed_register_width(struct kvm_vcpu *vcpu)
> > if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1) && is32bit)
> > return false;
> >
> > - /* MTE is incompatible with AArch32 */
> > - if (kvm_has_mte(vcpu->kvm) && is32bit)
> > + /* MTE and NV are incompatible with AArch32 */
> > + if ((kvm_has_mte(vcpu->kvm) || nested_virt_in_use(vcpu)) && is32bit)
> > return false;
>
> Should something similar be done for SVE? I see from the ID register emulation
> that SVE is hidden from the guest but there isn't anything in
> kvm_vcpu_enable_sve() that checks if NV is in use. That means it's possible to
> have both nested_virt_in_use(vcpu) and vcpu_has_sve(vcpu) be true
> simultaneously. If that happens, the FPSIMD fixup can get confused
>
> /*
> * Don't handle SVE traps for non-SVE vcpus here. This
> * includes NV guests for the time being.
> */
> if (!sve_guest && (esr_ec != ESR_ELx_EC_FP_ASIMD ||
> guest_hyp_fpsimd_traps_enabled(vcpu)))
> return false;
>
> and incorrectly restore the wrong context instead of forwarding a
> FPSIMD trap to the guest hypervisor.
Yes, nice catch. I have added this to kvm_reset_vcpu() to prevent the
issue.
if (nested_virt_in_use(vcpu) &&
vcpu_has_feature(vcpu, KVM_ARM_VCPU_SVE)) {
ret = -EINVAL;
goto out;
}
I may also rename nested_virt_in_use() to vcpu_has_nv(), which would
fit the rest of the code a bit better.
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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