On Tue, Jul 19, 2022 at 3:35 AM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > On Mon, 18 Jul 2022 18:03:30 +0100, > Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > > > > On Sun, Jul 17, 2022 at 11:56 PM Marc Zyngier <maz@xxxxxxxxxx> wrote: > > > > > > [- Drew and android-mm, as both addresses bounce] > > > > > > On Fri, 15 Jul 2022 07:10:17 +0100, > > > Kalesh Singh <kaleshsingh@xxxxxxxxxx> wrote: > > > > > > > > This can be used to disable stacktrace for the protected KVM > > > > nVHE hypervisor, in order to save on the associated memory usage. > > > > > > > > This option is disabled by default, since protected KVM is not widely > > > > used on platforms other than Android currently. > > > > > > > > Signed-off-by: Kalesh Singh <kaleshsingh@xxxxxxxxxx> > > > > --- > > > > arch/arm64/kvm/Kconfig | 15 +++++++++++++++ > > > > 1 file changed, 15 insertions(+) > > > > > > > > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig > > > > index 8a5fbbf084df..1edab6f8a3b8 100644 > > > > --- a/arch/arm64/kvm/Kconfig > > > > +++ b/arch/arm64/kvm/Kconfig > > > > @@ -46,6 +46,21 @@ menuconfig KVM > > > > > > > > If unsure, say N. > > > > > > > > +config PROTECTED_NVHE_STACKTRACE > > > > + bool "Protected KVM hypervisor stacktraces" > > > > + depends on KVM > > > > + default n > > > > + help > > > > + Say Y here to enable pKVM hypervisor stacktraces on hyp_panic() > > > > + > > > > + If you are not using protected nVHE (pKVM), say N. > > > > + > > > > + If using protected nVHE mode, but cannot afford the associated > > > > + memory cost (less than 0.75 page per CPU) of pKVM stacktraces, > > > > + say N. > > > > + > > > > + If unsure, say N. > > > > + > > > > > > Can we make this depend on NVHE_EL2_DEBUG instead? I'd like to keep > > > the disclosing of EL2 information in protected mode a strict debug > > > feature. > > > > Hi Marc, > > > > An earlier version was similar to what you propose. The unwinding > > depended on NVHE_EL2_DEBUG and all unwinding was done from EL1 with > > host stage 2 being disabled. The reason the design was changed is > > because Android expressed the need for pKVM hyp stacktraces in > > production environments. [1] > > I think that's an Android-specific requirement that doesn't apply to > upstream. If Android wants to enable this in production (and > potentially leak details of the hypervisor address space), that's > Android's business, and they can carry a patch for that. Upstream > shouldn't have to cater for such a thing. Hi Marc, For android it's important to be able to debug issues from the field. But I agree no need to subject upstream to the same requirements. I'll guard this with the NVHE_EL2_DEBUG config in the next version. Thanks, Kalesh > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
