On Fri, Apr 12, 2019 at 08:50:35AM +0530, Amit Daniel Kachhap wrote: > This patch advertises the capability of two cpu feature called address > pointer authentication and generic pointer authentication. These > capabilities depend upon system support for pointer authentication and > VHE mode. > > The current arm64 KVM partially implements pointer authentication and > support of address/generic authentication are tied together. However, > separate ABI requirements for both of them is added so that any future > isolated implementation will not require any ABI changes. > > Signed-off-by: Amit Daniel Kachhap <amit.kachhap@xxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx> > Cc: Christoffer Dall <christoffer.dall@xxxxxxx> > Cc: kvmarm@xxxxxxxxxxxxxxxxxxxxx > --- > Changes since v8: > * Keep the capability check same for the 2 vcpu ptrauth features. [Dave Martin] > > Documentation/virtual/kvm/api.txt | 2 ++ > arch/arm64/kvm/reset.c | 5 +++++ > include/uapi/linux/kvm.h | 2 ++ > 3 files changed, 9 insertions(+) > > diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt > index 9d202f4..56021d0 100644 > --- a/Documentation/virtual/kvm/api.txt > +++ b/Documentation/virtual/kvm/api.txt > @@ -2756,9 +2756,11 @@ Possible features: > - KVM_ARM_VCPU_PTRAUTH_ADDRESS: Enables Address Pointer authentication > for the CPU and supported only on arm64 architecture. > Must be requested if KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. > + Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. What if KVM_CAP_ARM_PTRAUTH_ADDRESS is absent and KVM_ARM_VCPU_PTRAUTH_GENERIC is requested? By these rules, we have a contradiction: userspace both must request and must not request KVM_ARM_VCPU_PTRAUTH_ADDRESS. We could qualify as follows: Depends on KVM_CAP_ARM_PTRAUTH_ADDRESS. Must be requested if KVM_CAP_ARM_PTRAUTH_ADDRESS is present and KVM_ARM_VCPU_PTRAUTH_GENERIC is also requested. > - KVM_ARM_VCPU_PTRAUTH_GENERIC: Enables Generic Pointer authentication > for the CPU and supported only on arm64 architecture. > Must be requested if KVM_ARM_VCPU_PTRAUTH_ADDRESS is also requested. > + Depends on KVM_CAP_ARM_PTRAUTH_GENERIC. Similarly. Or, we go back to having a single cap and a single feature, and add more caps/features later on if we decide it's possible to support address/generic auth separately later on. Otherwise, we end up with complex rules that can't be tested. This is a high price to pay for forwards compatibility: userspace's conformance to the rules can't be fully tested, so there's a fair chance it won't work properly anyway when hardware/KVM with just one auth type appears. [...] Thoughts? Cheers ---Dave _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
