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>
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