Re: [PATCH V11 16/17] RISC-V: paravirt: pvqspinlock: KVM: Add paravirt qspinlock skeleton

[Leonardo Bras <leobras@redhat.com>]

On Sun, Sep 10, 2023 at 04:29:10AM -0400, guoren@kernel.org wrote:
> From: Guo Ren <guoren@linux.alibaba.com>
> 
> Add the files functions needed to support the SBI PVLOCK (paravirt
> qspinlock kick_cpu) extension. This is a preparation for the next
> core implementation of kick_cpu.
> 
> Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> Signed-off-by: Guo Ren <guoren@kernel.org>
> ---
>  arch/riscv/include/asm/kvm_vcpu_sbi.h |  1 +
>  arch/riscv/include/uapi/asm/kvm.h     |  1 +
>  arch/riscv/kvm/Makefile               |  1 +
>  arch/riscv/kvm/vcpu_sbi.c             |  4 +++
>  arch/riscv/kvm/vcpu_sbi_pvlock.c      | 38 +++++++++++++++++++++++++++
>  5 files changed, 45 insertions(+)
>  create mode 100644 arch/riscv/kvm/vcpu_sbi_pvlock.c
> 
> diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> index cdcf0ff07be7..7b4d60b54d7e 100644
> --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> @@ -71,6 +71,7 @@ extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_srst;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_hsm;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_experimental;
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_vendor;
> +extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pvlock;
>  
>  #ifdef CONFIG_RISCV_PMU_SBI
>  extern const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pmu;
> diff --git a/arch/riscv/include/uapi/asm/kvm.h b/arch/riscv/include/uapi/asm/kvm.h
> index 992c5e407104..d005c229f2da 100644
> --- a/arch/riscv/include/uapi/asm/kvm.h
> +++ b/arch/riscv/include/uapi/asm/kvm.h
> @@ -148,6 +148,7 @@ enum KVM_RISCV_SBI_EXT_ID {
>  	KVM_RISCV_SBI_EXT_PMU,
>  	KVM_RISCV_SBI_EXT_EXPERIMENTAL,
>  	KVM_RISCV_SBI_EXT_VENDOR,
> +	KVM_RISCV_SBI_EXT_PVLOCK,
>  	KVM_RISCV_SBI_EXT_MAX,
>  };
>  
> diff --git a/arch/riscv/kvm/Makefile b/arch/riscv/kvm/Makefile
> index 4c2067fc59fc..6112750a3a0c 100644
> --- a/arch/riscv/kvm/Makefile
> +++ b/arch/riscv/kvm/Makefile
> @@ -26,6 +26,7 @@ kvm-$(CONFIG_RISCV_SBI_V01) += vcpu_sbi_v01.o
>  kvm-y += vcpu_sbi_base.o
>  kvm-y += vcpu_sbi_replace.o
>  kvm-y += vcpu_sbi_hsm.o
> +kvm-y += vcpu_sbi_pvlock.o
>  kvm-y += vcpu_timer.o
>  kvm-$(CONFIG_RISCV_PMU_SBI) += vcpu_pmu.o vcpu_sbi_pmu.o
>  kvm-y += aia.o
> diff --git a/arch/riscv/kvm/vcpu_sbi.c b/arch/riscv/kvm/vcpu_sbi.c
> index 9cd97091c723..c03c3d489b2b 100644
> --- a/arch/riscv/kvm/vcpu_sbi.c
> +++ b/arch/riscv/kvm/vcpu_sbi.c
> @@ -74,6 +74,10 @@ static const struct kvm_riscv_sbi_extension_entry sbi_ext[] = {
>  		.ext_idx = KVM_RISCV_SBI_EXT_VENDOR,
>  		.ext_ptr = &vcpu_sbi_ext_vendor,
>  	},
> +	{
> +		.ext_idx = KVM_RISCV_SBI_EXT_PVLOCK,
> +		.ext_ptr = &vcpu_sbi_ext_pvlock,
> +	},
>  };
>  
>  void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run)
> diff --git a/arch/riscv/kvm/vcpu_sbi_pvlock.c b/arch/riscv/kvm/vcpu_sbi_pvlock.c
> new file mode 100644
> index 000000000000..544a456c5041
> --- /dev/null
> +++ b/arch/riscv/kvm/vcpu_sbi_pvlock.c
> @@ -0,0 +1,38 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (c), 2023 Alibaba Cloud
> + *
> + * Authors:
> + *     Guo Ren <guoren@linux.alibaba.com>
> + */
> +
> +#include <linux/errno.h>
> +#include <linux/err.h>
> +#include <linux/kvm_host.h>
> +#include <asm/sbi.h>
> +#include <asm/kvm_vcpu_sbi.h>
> +
> +static int kvm_sbi_ext_pvlock_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> +				      struct kvm_vcpu_sbi_return *retdata)
> +{
> +	int ret = 0;
> +	struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> +	unsigned long funcid = cp->a6;
> +
> +	switch (funcid) {
> +	case SBI_EXT_PVLOCK_KICK_CPU:
> +		break;

IIUC, the kick implementation comes in the next patch but here it becomes a 
no-op. Is there any chance this may break a future bisect?

I don't understand a lot, but I would suggest either removing this no-op 
case SBI_EXT_PVLOCK_KICK_CPU, or merging this patch with the next one.

Other than that, LGTM.

Thanks,
Leo



> +	default:
> +		ret = SBI_ERR_NOT_SUPPORTED;
> +	}
> +
> +	retdata->err_val = ret;
> +
> +	return 0;
> +}
> +
> +const struct kvm_vcpu_sbi_extension vcpu_sbi_ext_pvlock = {
> +	.extid_start = SBI_EXT_PVLOCK,
> +	.extid_end = SBI_EXT_PVLOCK,
> +	.handler = kvm_sbi_ext_pvlock_handler,
> +};
> -- 
> 2.36.1
>