Re: [PATCH 4/8] target/riscv/kvm: consider irqchip_split() in aia_create()

[Alistair Francis]

On Fri, Oct 11, 2024 at 5:05 AM Daniel Henrique Barboza
<dbarboza@ventanamicro.com> wrote:
>
> Before adding support to kernel-irqchip=split when using KVM AIA we need
> to change how we create the in-kernel AIA device.
>
> In the use case we have so far, i.e. in-kernel irqchip without split
> mode, both the s-mode APLIC and IMSIC controllers are provided by the
> irqchip. In irqchip_split() mode we'll emulate the s-mode APLIC
> controller, which will send MSIs to the in-kernel IMSIC controller. To
> do that we need to change kvm_riscv_aia_create() to not create the
> in-kernel s-mode APLIC controller.
>
> In the kernel source arch/riscv/kvm/aia_aplic.c, function
> kvm_riscv_aia_aplic_init(), we verify that the APLIC controller won't be
> instantiated by KVM if we do not set 'nr_sources', which is set via
> KVM_DEV_RISCV_AIA_CONFIG_SRCS. For QEMU this means that we should not
> set 'aia_irq_num' during kvm_riscv_aia_create() in irqchip_split() mode.
>
> In this same condition, skip KVM_DEV_RISCV_AIA_ADDR_APLIC as well since
> it is used to set the base address for the in-kernel APLIC controller.
>
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/kvm/kvm-cpu.c | 36 ++++++++++++++++++++++--------------
>  1 file changed, 22 insertions(+), 14 deletions(-)
>
> diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
> index 8233a32102..a92a46694a 100644
> --- a/target/riscv/kvm/kvm-cpu.c
> +++ b/target/riscv/kvm/kvm-cpu.c
> @@ -1725,12 +1725,28 @@ void kvm_riscv_aia_create(MachineState *machine, 
> uint64_t group_shift,
>                       kvm_aia_mode_str(aia_mode));
>      }
>
> -    ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG,
> -                            KVM_DEV_RISCV_AIA_CONFIG_SRCS,
> -                            &aia_irq_num, true, NULL);
> -    if (ret < 0) {
> -        error_report("KVM AIA: failed to set number of input irq lines");
> -        exit(1);
> +    /*
> +     * Skip APLIC creation in KVM if we're running split mode.
> +     * This is done by leaving KVM_DEV_RISCV_AIA_CONFIG_SRCS
> +     * unset. We can also skip KVM_DEV_RISCV_AIA_ADDR_APLIC
> +     * since KVM won't be using it.
> +     */
> +    if (!kvm_kernel_irqchip_split()) {
> +        ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG,
> +                                KVM_DEV_RISCV_AIA_CONFIG_SRCS,
> +                                &aia_irq_num, true, NULL);
> +        if (ret < 0) {
> +            error_report("KVM AIA: failed to set number of input irq lines");
> +            exit(1);
> +        }
> +
> +        ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_ADDR,
> +                                KVM_DEV_RISCV_AIA_ADDR_APLIC,
> +                                &aplic_base, true, NULL);
> +        if (ret < 0) {
> +            error_report("KVM AIA: failed to set the base address of APLIC");
> +            exit(1);
> +        }
>      }
>
>      ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_CONFIG,
> @@ -1772,14 +1788,6 @@ void kvm_riscv_aia_create(MachineState *machine, 
> uint64_t group_shift,
>          exit(1);
>      }
>
> -    ret = kvm_device_access(aia_fd, KVM_DEV_RISCV_AIA_GRP_ADDR,
> -                            KVM_DEV_RISCV_AIA_ADDR_APLIC,
> -                            &aplic_base, true, NULL);
> -    if (ret < 0) {
> -        error_report("KVM AIA: failed to set the base address of APLIC");
> -        exit(1);
> -    }
> -
>      for (socket = 0; socket < socket_count; socket++) {
>          socket_imsic_base = imsic_base + socket * (1U << group_shift);
>          hart_count = riscv_socket_hart_count(machine, socket);
> --
> 2.45.2
>
>