Re: [PATCH 08/59] KVM: arm64: nv: Reset VMPIDR_EL2 and VPIDR_EL2 to sane values

Dave Martin
2019-06-24T12:59:37Z

On Fri, Jun 21, 2019 at 10:37:52AM +0100, Marc Zyngier wrote:
> The VMPIDR_EL2 and VPIDR_EL2 are architecturally UNKNOWN at reset, but
> let's be nice to a guest hypervisor behaving foolishly and reset these
> to something reasonable anyway.

Why be nice? Generally we do try to initialise UNKNOWN regs to garbage,
to help trip up badly-written guests.

Cheers
---Dave

>
> Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/kvm/sys_regs.c | 25 +++++++++++++++++++++----
> 1 file changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index e81be6debe07..693dd063c9c2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -624,7 +624,7 @@ static void reset_amair_el1(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> vcpu_write_sys_reg(vcpu, amair, AMAIR_EL1);
> }
>
> -static void reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +static u64 compute_reset_mpidr(struct kvm_vcpu *vcpu)
> {
> u64 mpidr;
>
> @@ -638,7 +638,24 @@ static void reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> mpidr = (vcpu->vcpu_id & 0x0f) << MPIDR_LEVEL_SHIFT(0);
> mpidr |= ((vcpu->vcpu_id >> 4) & 0xff) << MPIDR_LEVEL_SHIFT(1);
> mpidr |= ((vcpu->vcpu_id >> 12) & 0xff) << MPIDR_LEVEL_SHIFT(2);
> - vcpu_write_sys_reg(vcpu, (1ULL << 31) | mpidr, MPIDR_EL1);
> + mpidr |= (1ULL << 31);
> +
> + return mpidr;
> +}
> +
> +static void reset_mpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +{
> + vcpu_write_sys_reg(vcpu, compute_reset_mpidr(vcpu), MPIDR_EL1);
> +}
> +
> +static void reset_vmpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +{
> + vcpu_write_sys_reg(vcpu, compute_reset_mpidr(vcpu), VMPIDR_EL2);
> +}
> +
> +static void reset_vpidr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> +{
> + vcpu_write_sys_reg(vcpu, read_cpuid_id(), VPIDR_EL2);
> }
>
> static void reset_pmcr(struct kvm_vcpu *vcpu, const struct sys_reg_desc *r)
> @@ -1668,8 +1685,8 @@ static const struct sys_reg_desc sys_reg_descs[] = {
> */
> { SYS_DESC(SYS_PMCCFILTR_EL0), access_pmu_evtyper, reset_val, PMCCFILTR_EL0, 0 },
>
> - { SYS_DESC(SYS_VPIDR_EL2), access_rw, reset_val, VPIDR_EL2, 0 },
> - { SYS_DESC(SYS_VMPIDR_EL2), access_rw, reset_val, VMPIDR_EL2, 0 },
> + { SYS_DESC(SYS_VPIDR_EL2), access_rw, reset_vpidr, VPIDR_EL2 },
> + { SYS_DESC(SYS_VMPIDR_EL2), access_rw, reset_vmpidr, VMPIDR_EL2 },
>
> { SYS_DESC(SYS_SCTLR_EL2), access_rw, reset_val, SCTLR_EL2, 0 },
> { SYS_DESC(SYS_ACTLR_EL2), access_rw, reset_val, ACTLR_EL2, 0 },
> --
> 2.20.1
>
>
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