Hi Amit, On 19/03/2019 08:30, Amit Daniel Kachhap wrote: > This adds sections for KVM API extension for pointer authentication. > A brief description about usage of pointer authentication for KVM guests > is added in the arm64 documentations. > > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Christoffer Dall <christoffer.dall@xxxxxxx> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx> > Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx > --- > Documentation/arm64/pointer-authentication.txt | 15 +++++++++++---- > Documentation/virtual/kvm/api.txt | 6 ++++++ > 2 files changed, 17 insertions(+), 4 deletions(-) > > diff --git a/Documentation/arm64/pointer-authentication.txt b/Documentation/arm64/pointer-authentication.txt > index 5baca42..4b769e6 100644 > --- a/Documentation/arm64/pointer-authentication.txt > +++ b/Documentation/arm64/pointer-authentication.txt > @@ -87,7 +87,14 @@ used to get and set the keys for a thread. > Virtualization > -------------- > > -Pointer authentication is not currently supported in KVM guests. KVM > -will mask the feature bits from ID_AA64ISAR1_EL1, and attempted use of > -the feature will result in an UNDEFINED exception being injected into > -the guest. > +Pointer authentication is enabled in KVM guest when each virtual cpu is > +initialised by passing flags KVM_ARM_VCPU_PTRAUTH_[ADDRESS/GENERIC] and > +requesting this feature to be enabled. Without this flag, pointer "Without these flags"* > +authentication is not enabled in KVM guests and attempted use of the > +feature will result in an UNDEFINED exception being injected into the > +guest. > + > +Additionally, when these vcpu feature flags are not set then KVM will > +filter out the Pointer Authentication system key registers from > +KVM_GET/SET_REG_* ioctls and mask those features from cpufeature ID > +register. > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > index 7de9eee..b5c66bc 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -2659,6 +2659,12 @@ Possible features: > Depends on KVM_CAP_ARM_PSCI_0_2. > - KVM_ARM_VCPU_PMU_V3: Emulate PMUv3 for the CPU. > Depends on KVM_CAP_ARM_PMU_V3. > + - KVM_ARM_VCPU_PTRAUTH_ADDRESS: > + - KVM_ARM_VCPU_PTRAUTH_GENERIC: > + Enables Pointer authentication for the CPU. > + Depends on KVM_CAP_ARM_PTRAUTH and only on arm64 architecture. If > + set, then the KVM guest allows the execution of pointer authentication > + instructions. Otherwise, KVM treats these instructions as undefined. > Overall I feel one could easily get confused to whether PTRAUTH_ADDRESS/GENERIC are two individual features, whether one is a superset of the other, if the names are just an alias of one another, etc... I think the doc should at least stress out that *both* flags are required to enable ptrauth in a guest. However it raises the question, if we don't plan to support the features individually (because we can't), should we really expose two feature flags? I seems odd to introduce two flags that only do something if used together... Cheers, -- Julien Thierry _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
