Re: [PATCH v6 12/64] KVM: arm64: nv: Add non-VHE-EL2->EL1 translation helpers

Russell King (Oracle)
2022-02-01T16:39:41Z

On Fri, Jan 28, 2022 at 12:18:20PM +0000, Marc Zyngier wrote:
> Some EL2 system registers immediately affect the current execution
> of the system, so we need to use their respective EL1 counterparts.
> For this we need to define a mapping between the two. In general,
> this only affects non-VHE guest hypervisors, as VHE system registers
> are compatible with the EL1 counterparts.
>
> These helpers will get used in subsequent patches.
>
> Co-developed-by: Andre Przywara <andre.przywara@arm.com>
> Signed-off-by: Andre Przywara <andre.przywara@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

> ---
> arch/arm64/include/asm/kvm_nested.h | 54 +++++++++++++++++++++++++++++
> 1 file changed, 54 insertions(+)
>
> diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
> index fd601ea68d13..5a85be6d8eb3 100644
> --- a/arch/arm64/include/asm/kvm_nested.h
> +++ b/arch/arm64/include/asm/kvm_nested.h
> @@ -2,6 +2,7 @@
> #ifndef __ARM64_KVM_NESTED_H
> #define __ARM64_KVM_NESTED_H
>
> +#include <linux/bitfield.h>
> #include <linux/kvm_host.h>
>
> static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu)
> @@ -11,4 +12,57 @@ static inline bool vcpu_has_nv(const struct kvm_vcpu *vcpu)
> test_bit(KVM_ARM_VCPU_HAS_EL2, vcpu->arch.features));
> }
>
> +/* Translation helpers from non-VHE EL2 to EL1 */
> +static inline u64 tcr_el2_ps_to_tcr_el1_ips(u64 tcr_el2)
> +{
> + return (u64)FIELD_GET(TCR_EL2_PS_MASK, tcr_el2) << TCR_IPS_SHIFT;

I frowned about the use of FIELD_GET() but not FIELD_PREP(), which
would be:

return FIELD_PREP(TCR_IPS_MASK, FIELD_GET(TCR_EL2_PS_MASK, tcr_el2));

However, I'm not bothered by this beyond frowning!

--
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