On Sat, Nov 23, 2019 at 11:56:18AM +0000, Marc Zyngier wrote: > HCR_EL2.TID3 mandates that access from EL1 to a long list of id > registers traps to EL2, and QEMU has so far ignored this requirement. > > This breaks (among other things) KVM guests that have PtrAuth enabled, > while the hypervisor doesn't want to expose the feature to its guest. > To achieve this, KVM traps the ID registers (ID_AA64ISAR1_EL1 in this > case), and masks out the unsupported feature. > > QEMU not honoring the trap request means that the guest observes > that the feature is present in the HW, starts using it, and dies > a horrible death when KVM injects an UNDEF, because the feature > *really* isn't supported. > > Do the right thing by trapping to EL2 if HCR_EL2.TID3 is set. > > Reported-by: Will Deacon <will@xxxxxxxxxx> > Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx> > --- > There is a number of other trap bits missing (TID[0-2], for example), > but this at least gets a mainline Linux going with cpu=max. > > target/arm/helper.c | 75 +++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 75 insertions(+) I took your fixes/el2_traps branch for a spin and I no longer get an unexpected undefined instruction trap on first access to the ptrauth key registers during context-switch: Tested-by: Will Deacon <will@xxxxxxxxxx> Thanks, Will _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
