Re: [PATCH 01/16] KVM: arm64: Generalise VM features into a set of flags
From: Will Deacon <will@kernel.org>
Date: 2021-07-27 18:10:35
Also in:
kvmarm, linux-arm-kernel, lkml
On Thu, Jul 15, 2021 at 05:31:44PM +0100, Marc Zyngier wrote:
quoted hunk ↗ jump to hunk
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@kernel.org> --- 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.
quoted hunk ↗ jump to hunk
/* * 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