On Wed, Apr 24, 2019 at 11:29:37AM +0100, Marc Zyngier wrote: > On 23/04/2019 16:44, Dave Martin wrote: > > On Tue, Apr 23, 2019 at 03:54:32PM +0530, Amit Daniel Kachhap wrote: > >> Hi Mark, > >> > >> On 4/23/19 3:09 PM, Marc Zyngier wrote: > >>> On Tue, 23 Apr 2019 05:42:35 +0100, > >>> Amit Daniel Kachhap <amit.kachhap@xxxxxxx> wrote: [...] > >>>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > >>>> index 7e34b9e..3cfe2eb 100644 > >>>> --- a/arch/arm64/Kconfig > >>>> +++ b/arch/arm64/Kconfig > >>>> @@ -1301,8 +1301,9 @@ config ARM64_PTR_AUTH > >>>> context-switched along with the process. > >>>> The feature is detected at runtime. If the feature is not present in > >>>> - hardware it will not be advertised to userspace nor will it be > >>>> - enabled. > >>>> + hardware it will not be advertised to userspace/KVM guest nor will it > >>>> + be enabled. However, KVM guest also require VHE mode and hence > >>>> + CONFIG_ARM64_VHE=y option to use this feature. > >>> > >>> SVE seems to have the exact same requirements, and has > >>> > >>> depends on !KVM || ARM64_VHE > >>> > >>> Why don't we have that for PTR_AUTH too? > >> This point came up earlier also and it was suggested by Dave[1] to leave > >> userspace ptrauth for non-vhe mode as that would bring regression now. > >> [1]:https://lkml.org/lkml/2019/3/27/583 > > > > I see Marc applied this change in > > https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git/commit/?h=queue&id=e19b245fa4c61558536bd34f80845f0c41eab65f0 > > That's only for me not to forget anything, and it hasn't been folded > into the original patch yet. Ah, right, misunderstood. > > The risk here is that someone has a custom config from an old kernel > > that explicitly turns CONFIG_ARM64_VHE off, and that try to use that > > config with this patch. > > > > I'm not sure how much we care about that. > > > > Otherwise, blocking this config so that people don't accidentally rely > > on it seems sensible. > > What I'm trying to do is to reduce the amount of valid kernel > configurations that we need to validate independently. > > At this stage, I'm tempted to just restrict it as described above, and > maybe relax it if someone shouts at me. Sounds good to me. Cheers ---Dave _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
