On Wed, Feb 16, 2022 at 04:39:03PM +1000, Nicholas Piggin wrote: > Use KVM_CAP_PPC_AIL_MODE_3 to determine cap-ail-mode-3 support for KVM > guests. Keep the fallback heuristic for KVM hosts that pre-date this > CAP. > > This is only proposed the KVM CAP has not yet been allocated. I will > ask to merge the new KVM cap when there are no objections on the QEMU > side. > > not-yet-Signed-off-by: Nicholas Piggin <npig...@gmail.com>
LGTM, once the kernel side work is done.
> ---
> Since v1:
> - Remove incorrect test for unsupported cap query. Add comment instead.
>
> linux-headers/linux/kvm.h | 1 +
> target/ppc/kvm.c | 18 ++++++++++++++++++
> 2 files changed, 19 insertions(+)
>
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index 02c5e7b7bb..d91f578200 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -1130,6 +1130,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_BINARY_STATS_FD 203
> #define KVM_CAP_EXIT_ON_EMULATION_FAILURE 204
> #define KVM_CAP_ARM_MTE 205
> +#define KVM_CAP_PPC_AIL_MODE_3 210
You may be aware of this already, but once the cap is allocated on the
kernel side, you should do a full update of the kernel headers as a
separate patch. A direct hack to the headers copy is fine for a
preliminary posting, though.
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/target/ppc/kvm.c b/target/ppc/kvm.c
> index 1338c41f8f..7f71f78253 100644
> --- a/target/ppc/kvm.c
> +++ b/target/ppc/kvm.c
> @@ -90,6 +90,7 @@ static int cap_ppc_nested_kvm_hv;
> static int cap_large_decr;
> static int cap_fwnmi;
> static int cap_rpt_invalidate;
> +static int cap_ail_mode_3;
>
> static uint32_t debug_inst_opcode;
>
> @@ -154,6 +155,7 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
> }
>
> cap_rpt_invalidate = kvm_vm_check_extension(s,
> KVM_CAP_PPC_RPT_INVALIDATE);
> + cap_ail_mode_3 = kvm_vm_check_extension(s, KVM_CAP_PPC_AIL_MODE_3);
> kvm_ppc_register_host_cpu_type();
>
> return 0;
> @@ -2567,6 +2569,17 @@ bool kvmppc_supports_ail_3(void)
> {
> PowerPCCPUClass *pcc = kvm_ppc_get_host_cpu_class();
>
> + if (cap_ail_mode_3) {
> + return 1;
> + }
> +
> + /*
> + * cap-ail-mode-3 is disabled, but it may be because the KVM host
> pre-dates
> + * the cap. Special-case the test because the performance cost for
> + * disabling the feature unconditionally is prohibitive until updated
> + * KVM is widely in use.
> + */
> +
> /*
> * KVM PR only supports AIL-0
> */
> @@ -2589,6 +2602,11 @@ bool kvmppc_supports_ail_3(void)
> return 0;
> }
>
> + /*
> + * Beyond ISA v3.1 (POWER10), this could return 0, because all KVM
> + * implementations for such hosts would support the cap.
> + */
> +
> return 1;
> }
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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