On Mon, Dec 23, 2019 at 12:05:12PM +0000, Marc Zyngier wrote: > On 2019-12-23 11:56, Andrew Murray wrote: > > On Sun, Dec 22, 2019 at 10:42:05AM +0000, Marc Zyngier wrote: > > > On Fri, 20 Dec 2019 14:30:18 +0000, > > > Andrew Murray <andrew.murray@xxxxxxx> wrote: > > > > > > > > As we now save/restore the profiler state there is no need to trap > > > > accesses to the statistical profiling controls. Let's unset the > > > > _TPMS bit. > > > > > > > > Signed-off-by: Andrew Murray <andrew.murray@xxxxxxx> > > > > --- > > > > arch/arm64/kvm/debug.c | 2 -- > > > > 1 file changed, 2 deletions(-) > > > > > > > > diff --git a/arch/arm64/kvm/debug.c b/arch/arm64/kvm/debug.c > > > > index 43487f035385..07ca783e7d9e 100644 > > > > --- a/arch/arm64/kvm/debug.c > > > > +++ b/arch/arm64/kvm/debug.c > > > > @@ -88,7 +88,6 @@ void kvm_arm_reset_debug_ptr(struct kvm_vcpu > > > *vcpu) > > > > * - Performance monitors (MDCR_EL2_TPM/MDCR_EL2_TPMCR) > > > > * - Debug ROM Address (MDCR_EL2_TDRA) > > > > * - OS related registers (MDCR_EL2_TDOSA) > > > > - * - Statistical profiler (MDCR_EL2_TPMS/MDCR_EL2_E2PB) > > > > * > > > > * Additionally, KVM only traps guest accesses to the debug > > > registers if > > > > * the guest is not actively using them (see the > > > KVM_ARM64_DEBUG_DIRTY > > > > @@ -111,7 +110,6 @@ void kvm_arm_setup_debug(struct kvm_vcpu > > > *vcpu) > > > > */ > > > > vcpu->arch.mdcr_el2 = __this_cpu_read(mdcr_el2) & > > > MDCR_EL2_HPMN_MASK; > > > > vcpu->arch.mdcr_el2 |= (MDCR_EL2_TPM | > > > > - MDCR_EL2_TPMS | > > > > > > No. This is an *optional* feature (the guest could not be presented > > > with the SPE feature, or the the support simply not be compiled in). > > > > > > If the guest is not allowed to see the feature, for whichever > > > reason, > > > the traps *must* be enabled and handled. > > > > I'll update this (and similar) to trap such registers when we don't > > support > > SPE in the guest. > > > > My original concern in the cover letter was in how to prevent the guest > > from attempting to use these registers in the first place - I think the > > solution I was looking for is to trap-and-emulate ID_AA64DFR0_EL1 such > > that > > the PMSVer bits indicate that SPE is not emulated. > > That, and active trapping of the SPE system registers resulting in injection > of an UNDEF into the offending guest. Yes that's no problem. Thanks, Andrew Murray > > Thanks, > > M. > -- > Jazz is not dead. It just smells funny...
