On Mon, 29 Jun 2020 at 09:15, Andrew Jones <drjones@xxxxxxxxxx> wrote:
>
> On Sun, Jun 28, 2020 at 04:04:58PM +0100, Beata Michalska wrote:
> > On ARMv7 & ARMv8 some load/store instructions might trigger a data abort
> > exception with no valid ISS info to be decoded. The lack of decode info
> > makes it at least tricky to emulate those instruction which is one of the
> > (many) reasons why KVM will not even try to do so.
> >
> > Add support for handling those by requesting KVM to inject external
> > dabt into the quest.
> >
> > Signed-off-by: Beata Michalska <beata.michalska@xxxxxxxxxx>
> > ---
> > target/arm/kvm.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++++-
> > 1 file changed, 56 insertions(+), 1 deletion(-)
> >
> > diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> > index eef3bbd..2dd8a9a 100644
> > --- a/target/arm/kvm.c
> > +++ b/target/arm/kvm.c
> > @@ -39,6 +39,7 @@ const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
> >
> > static bool cap_has_mp_state;
> > static bool cap_has_inject_serror_esr;
> > +static bool cap_has_inject_ext_dabt;
> >
> > static ARMHostCPUFeatures arm_host_cpu_features;
> >
> > @@ -245,6 +246,16 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> > ret = -EINVAL;
> > }
> >
> > + if (kvm_check_extension(s, KVM_CAP_ARM_NISV_TO_USER)) {
> > + if (kvm_vm_enable_cap(s, KVM_CAP_ARM_NISV_TO_USER, 0)) {
> > + error_report("Failed to enable KVM_CAP_ARM_NISV_TO_USER cap");
> > + } else {
> > + /* Set status for supporting the external dabt injection */
> > + cap_has_inject_ext_dabt = kvm_check_extension(s,
> > + KVM_CAP_ARM_INJECT_EXT_DABT);
> > + }
> > + }
> > +
> > return ret;
> > }
> >
> > @@ -810,6 +821,45 @@ void kvm_arm_vm_state_change(void *opaque, int running, RunState state)
> > }
> > }
> >
> > +/**
> > + * kvm_arm_handle_dabt_nisv:
> > + * @cs: CPUState
> > + * @esr_iss: ISS encoding (limited) for the exception from Data Abort
> > + * ISV bit set to '0b0' -> no valid instruction syndrome
> > + * @fault_ipa: faulting address for the synchronous data abort
> > + *
> > + * Returns: 0 if the exception has been handled, < 0 otherwise
> > + */
> > +static int kvm_arm_handle_dabt_nisv(CPUState *cs, uint64_t esr_iss,
> > + uint64_t fault_ipa)
>
> The indent of 'uint64_t fault_ipa' is off. Should be under CPUState.
>
> > +{
> > + /*
> > + * Request KVM to inject the external data abort into the guest
> > + */
> > + if (cap_has_inject_ext_dabt) {
> > + struct kvm_vcpu_events events = { };
> > + /*
> > + * The external data abort event will be handled immediately by KVM
> > + * using the address fault that triggered the exit on given VCPU.
> > + * Requesting injection of the external data abort does not rely
> > + * on any other VCPU state. Therefore, in this particular case, the VCPU
> > + * synchronization can be exceptionally skipped.
> > + */
> > + events.exception.ext_dabt_pending = 1;
> > + /*
> > + * KVM_CAP_ARM_INJECT_EXT_DABT implies KVM_CAP_VCPU_EVENTS
> > + */
>
> Single line comments may be done with /* ... */
>
> > + return kvm_vcpu_ioctl(cs, KVM_SET_VCPU_EVENTS, &events);
> > +
>
> Extra blank line here.
>
> > + } else {
> > + error_report("Data abort exception triggered by guest memory access "
> > + "at physical address: 0x" TARGET_FMT_lx,
> > + (target_ulong)fault_ipa);
> > + error_printf("KVM unable to emulate faulting instruction.\n");
> > + }
> > + return -1;
> > +}
> > +
> > int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
> > {
> > int ret = 0;
> > @@ -820,7 +870,12 @@ int kvm_arch_handle_exit(CPUState *cs, struct kvm_run *run)
> > ret = EXCP_DEBUG;
> > } /* otherwise return to guest */
> > break;
> > - default:
> > + case KVM_EXIT_ARM_NISV:
> > + /* External DABT with no valid iss to decode */
> > + ret = kvm_arm_handle_dabt_nisv(cs, run->arm_nisv.esr_iss,
> > + run->arm_nisv.fault_ipa);
> > + break;
> > + default:
>
> An extra space got added in front of 'default:'
>
> > qemu_log_mask(LOG_UNIMP, "%s: un-handled exit reason %d\n",
> > __func__, run->exit_reason);
> > break;
> > --
> > 2.7.4
> >
> >
>
> Besides the format changes
>
> Reviewed-by: Andrew Jones <drjones@xxxxxxxxxx>
>
Done.
Thanks a lot for the reviews!
BR
Beata
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