| Message ID | 20230920195036.1169791-2-oliver.upton@linux.dev (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: arm64: Cleanup + fix to vCPU reset, feature flags | expand |
On Wed, 20 Sep 2023 20:50:29 +0100, Oliver Upton <oliver.upton@linux.dev> wrote: > > To date KVM has relied on kvm_reset_vcpu() failing when the vCPU feature > flags are unsupported by the system. This is a bit messy since > kvm_reset_vcpu() is called at runtime outside of the KVM_ARM_VCPU_INIT > ioctl when it is expected to succeed. Further complicating the matter is > that kvm_reset_vcpu() must tolerate be idemptotent to the config_lock, > as it isn't consistently called with the lock held. > > Prepare to move feature compatibility checks out of kvm_reset_vcpu() with > a 'generic' check that compares the user-provided flags with a computed > maximum feature set for the system. > > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> > --- > arch/arm64/kvm/arm.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index 4866b3f7b4ea..66f3720cdd3a 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -1190,6 +1190,16 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level, > return -EINVAL; > } > > +static unsigned long system_supported_vcpu_features(void) > +{ > + unsigned long features = KVM_VCPU_VALID_FEATURES; > + > + if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) I think we can now convert this to a cpus_have_final_cap(), as Mark is getting rid of the helper altogether, see [1]. Thanks, M. [1] https://lore.kernel.org/r/20230919092850.1940729-1-mark.rutland@arm.com
On 20/9/23 21:50, Oliver Upton wrote: > To date KVM has relied on kvm_reset_vcpu() failing when the vCPU feature > flags are unsupported by the system. This is a bit messy since > kvm_reset_vcpu() is called at runtime outside of the KVM_ARM_VCPU_INIT > ioctl when it is expected to succeed. Further complicating the matter is > that kvm_reset_vcpu() must tolerate be idemptotent to the config_lock, > as it isn't consistently called with the lock held. > > Prepare to move feature compatibility checks out of kvm_reset_vcpu() with > a 'generic' check that compares the user-provided flags with a computed > maximum feature set for the system. > > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> > --- > arch/arm64/kvm/arm.c | 16 +++++++++++++--- > 1 file changed, 13 insertions(+), 3 deletions(-) Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 4866b3f7b4ea..66f3720cdd3a 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1190,6 +1190,16 @@ int kvm_vm_ioctl_irq_line(struct kvm *kvm, struct kvm_irq_level *irq_level, return -EINVAL; } +static unsigned long system_supported_vcpu_features(void) +{ + unsigned long features = KVM_VCPU_VALID_FEATURES; + + if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) + clear_bit(KVM_ARM_VCPU_EL1_32BIT, &features); + + return features; +} + static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu, const struct kvm_vcpu_init *init) { @@ -1204,12 +1214,12 @@ static int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu, return -ENOENT; } + if (features & ~system_supported_vcpu_features()) + return -EINVAL; + if (!test_bit(KVM_ARM_VCPU_EL1_32BIT, &features)) return 0; - if (!cpus_have_const_cap(ARM64_HAS_32BIT_EL1)) - return -EINVAL; - /* MTE is incompatible with AArch32 */ if (kvm_has_mte(vcpu->kvm)) return -EINVAL;
To date KVM has relied on kvm_reset_vcpu() failing when the vCPU feature flags are unsupported by the system. This is a bit messy since kvm_reset_vcpu() is called at runtime outside of the KVM_ARM_VCPU_INIT ioctl when it is expected to succeed. Further complicating the matter is that kvm_reset_vcpu() must tolerate be idemptotent to the config_lock, as it isn't consistently called with the lock held. Prepare to move feature compatibility checks out of kvm_reset_vcpu() with a 'generic' check that compares the user-provided flags with a computed maximum feature set for the system. Signed-off-by: Oliver Upton <oliver.upton@linux.dev> --- arch/arm64/kvm/arm.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-)