On Thu, Jul 15, 2021 at 05:31:44PM +0100, Marc Zyngier wrote:
> We currently deal with a set of booleans for VM features,
> while they could be better represented as set of flags
> contained in an unsigned long, similarily to what we are
> doing on the CPU side.
>
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> ---
> arch/arm64/include/asm/kvm_host.h | 12 +++++++-----
> arch/arm64/kvm/arm.c | 5 +++--
> arch/arm64/kvm/mmio.c | 3 ++-
> 3 files changed, 12 insertions(+), 8 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 41911585ae0c..4add6c27251f 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -122,7 +122,10 @@ struct kvm_arch {
> * should) opt in to this feature if KVM_CAP_ARM_NISV_TO_USER is
> * supported.
> */
> - bool return_nisv_io_abort_to_user;
> +#define KVM_ARCH_FLAG_RETURN_NISV_IO_ABORT_TO_USER 0
> + /* Memory Tagging Extension enabled for the guest */
> +#define KVM_ARCH_FLAG_MTE_ENABLED 1
> + unsigned long flags;
One downside of packing all these together is that updating 'flags' now
requires an atomic rmw sequence (i.e. set_bit()). Then again, that's
probably for the best anyway given that kvm_vm_ioctl_enable_cap() looks
like it doesn't hold any locks.
> /*
> * VM-wide PMU filter, implemented as a bitmap and big enough for
> @@ -133,9 +136,6 @@ struct kvm_arch {
>
> u8 pfr0_csv2;
> u8 pfr0_csv3;
> -
> - /* Memory Tagging Extension enabled for the guest */
> - bool mte_enabled;
> };
>
> struct kvm_vcpu_fault_info {
> @@ -777,7 +777,9 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
> #define kvm_arm_vcpu_sve_finalized(vcpu) \
> ((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>
> -#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
> +#define kvm_has_mte(kvm) \
> + (system_supports_mte() && \
> + test_bit(KVM_ARCH_FLAG_MTE_ENABLED, &(kvm)->arch.flags))
Not an issue with this patch, but I just noticed that the
system_supports_mte() check is redundant here as we only allow the flag to
be set if that's already the case.
Will
