Nicholas Piggin <npig...@gmail.com> writes:
> Add KVM_CAP_PPC_AIL_MODE_3 to advertise the capability to set the AIL
> resource mode to 3 with the H_SET_MODE hypercall. This capability
> differs between processor types and KVM types (PR, HV, Nested HV), and
> affects guest-visible behaviour.
>
> QEMU will implement a cap-ail-mode-3 to control this behaviour[1], and
> use the KVM CAP if available to determine KVM support[2].
>
> [1] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00437.html
> [2] https://lists.nongnu.org/archive/html/qemu-ppc/2022-02/msg00439.html
>
> Signed-off-by: Nicholas Piggin <npig...@gmail.com>
Reviewed-by: Fabiano Rosas <faro...@linux.ibm.com>
> ---
> Documentation/virt/kvm/api.rst | 14 ++++++++++++++
> arch/powerpc/include/asm/setup.h | 2 ++
> arch/powerpc/kvm/powerpc.c | 20 ++++++++++++++++++++
> arch/powerpc/platforms/pseries/setup.c | 12 +++++++++++-
> include/uapi/linux/kvm.h | 1 +
> tools/include/uapi/linux/kvm.h | 1 +
> 6 files changed, 49 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index bb8cfddbb22d..404056a9a35a 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6995,6 +6995,20 @@ indicated by the fd to the VM this is called on.
> This is intended to support intra-host migration of VMs between userspace
> VMMs,
> upgrading the VMM process without interrupting the guest.
>
> +7.30 KVM_CAP_PPC_AIL_MODE_3
> +-------------------------------
> +
> +:Capability: KVM_CAP_PPC_AIL_MODE_3
> +:Architectures: ppc
> +:Type: vm
> +
> +This capability indicates that the kernel supports the mode 3 setting for the
> +"Address Translation Mode on Interrupt" aka "Alternate Interrupt Location"
> +resource that is controlled with the H_SET_MODE hypercall.
> +
> +This capability allows a guest kernel to use a better-performance mode for
> +handling interrupts and system calls.
> +
> 8. Other capabilities.
> ======================
>
> diff --git a/arch/powerpc/include/asm/setup.h
> b/arch/powerpc/include/asm/setup.h
> index d0d3dd531c7f..a555fb77258a 100644
> --- a/arch/powerpc/include/asm/setup.h
> +++ b/arch/powerpc/include/asm/setup.h
> @@ -28,11 +28,13 @@ void setup_panic(void);
> #define ARCH_PANIC_TIMEOUT 180
>
> #ifdef CONFIG_PPC_PSERIES
> +extern bool pseries_reloc_on_exception(void);
> extern bool pseries_enable_reloc_on_exc(void);
> extern void pseries_disable_reloc_on_exc(void);
> extern void pseries_big_endian_exceptions(void);
> void __init pseries_little_endian_exceptions(void);
> #else
> +static inline bool pseries_reloc_on_exception(void) { return false; }
> static inline bool pseries_enable_reloc_on_exc(void) { return false; }
> static inline void pseries_disable_reloc_on_exc(void) {}
> static inline void pseries_big_endian_exceptions(void) {}
> diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> index 2ad0ccd202d5..7dc101ea778c 100644
> --- a/arch/powerpc/kvm/powerpc.c
> +++ b/arch/powerpc/kvm/powerpc.c
> @@ -678,6 +678,26 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long
> ext)
> r = 1;
> break;
> #endif
> + case KVM_CAP_PPC_AIL_MODE_3:
> + /*
> + * KVM PR, POWER7, and some POWER9s don't support AIL=3 mode.
> + * The POWER9s can support it if the guest runs in hash mode,
> + * but QEMU doesn't necessarily query the capability in time.
> + */
> + if (hv_enabled) {
> + if (kvmhv_on_pseries()) {
> + if (pseries_reloc_on_exception())
> + r = 1;
> + } else if (cpu_has_feature(CPU_FTR_ARCH_207S) &&
> +
> !cpu_has_feature(CPU_FTR_P9_RADIX_PREFETCH_BUG)) {
> + r = 1;
> + } else {
> + r = 0;
> + }
> + } else {
> + r = 0;
> + }
> + break;
> default:
> r = 0;
> break;
> diff --git a/arch/powerpc/platforms/pseries/setup.c
> b/arch/powerpc/platforms/pseries/setup.c
> index 83a04d967a59..182525c2abd5 100644
> --- a/arch/powerpc/platforms/pseries/setup.c
> +++ b/arch/powerpc/platforms/pseries/setup.c
> @@ -353,6 +353,13 @@ static void pseries_lpar_idle(void)
> pseries_idle_epilog();
> }
>
> +static bool pseries_reloc_on_exception_enabled;
> +
> +bool pseries_reloc_on_exception(void)
> +{
> + return pseries_reloc_on_exception_enabled;
> +}
> +
> /*
> * Enable relocation on during exceptions. This has partition wide scope and
> * may take a while to complete, if it takes longer than one second we will
> @@ -377,6 +384,7 @@ bool pseries_enable_reloc_on_exc(void)
> " on exceptions: %ld\n", rc);
> return false;
> }
> + pseries_reloc_on_exception_enabled = true;
> return true;
> }
>
> @@ -404,7 +412,9 @@ void pseries_disable_reloc_on_exc(void)
> break;
> mdelay(get_longbusy_msecs(rc));
> }
> - if (rc != H_SUCCESS)
> + if (rc == H_SUCCESS)
> + pseries_reloc_on_exception_enabled = false;
> + else
> pr_warn("Warning: Failed to disable relocation on exceptions:
> %ld\n",
> rc);
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 9563d294f181..65f231d048a8 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
> #define KVM_CAP_VM_GPA_BITS 207
> #define KVM_CAP_XSAVE2 208
> +#define KVM_CAP_PPC_AIL_MODE_3 209
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
> index 9563d294f181..65f231d048a8 100644
> --- a/tools/include/uapi/linux/kvm.h
> +++ b/tools/include/uapi/linux/kvm.h
> @@ -1133,6 +1133,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM 206
> #define KVM_CAP_VM_GPA_BITS 207
> #define KVM_CAP_XSAVE2 208
> +#define KVM_CAP_PPC_AIL_MODE_3 209
>
> #ifdef KVM_CAP_IRQ_ROUTING
