Hi Amit, On 09/01/2019 10:13, Amit Daniel Kachhap wrote: > On Sat, Jan 5, 2019 at 12:05 AM James Morse <james.morse@xxxxxxx> wrote: >> On 18/12/2018 07:56, Amit Daniel Kachhap wrote: >>> This feature will allow the KVM guest to allow the handling of >>> pointer authentication instructions or to treat them as undefined >>> if not set. It uses the existing vcpu API KVM_ARM_VCPU_INIT to >>> supply this parameter instead of creating a new API. >>> >>> A new register is not created to pass this parameter via >>> SET/GET_ONE_REG interface as just a flag (KVM_ARM_VCPU_PTRAUTH) >>> supplied is enough to select this feature. >> >> What is the motivation for doing this? Doesn't ptrauth 'just' need turning on? >> It doesn't need additional setup to be useable, or rely on some qemu support to >> work properly. There isn't any hidden state that can't be migrated in the usual way. >> Is it just because we don't want to commit to the ABI? > This allows migration of guest to non pointer authenticated supported > systems and hides the extra ptrauth registers. The MIDR already has to match, so the hardware must be the same. I guess this lets us hide the new feature so old-guests can migrate to a new-kernel without a write to the id registers failing. > Basically this suggestion was given by Christoffer > (https://lore.kernel.org/lkml/20180206123847.GY21802@cbox/). Ah, Christoffer asked for it, that's reason enough! Thanks, James _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
