linux-kernel - Re: [PATCH v2 2/2] RISCV: KVM: Introduce vcpu->reset_cntx

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Message-ID: <CAAhSdy2na-+4DrZm7W8ZD2zGMF7J3VVL235Wx2_QVPr1AfuFVg@mail.gmail.com>
Date: Mon, 22 Apr 2024 09:27:12 +0530
From: Anup Patel <anup@...infault.org>
To: Yong-Xuan Wang <yongxuan.wang@...ive.com>
Cc: linux-riscv@...ts.infradead.org, kvm-riscv@...ts.infradead.org, 
	greentime.hu@...ive.com, vincent.chen@...ive.com, 
	Atish Patra <atishp@...shpatra.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, Albert Ou <aou@...s.berkeley.edu>, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/2] RISCV: KVM: Introduce vcpu->reset_cntx_lock

On Wed, Apr 17, 2024 at 1:15 PM Yong-Xuan Wang <yongxuan.wang@...ive.com> wrote:
>
> Originally, the use of kvm->lock in SBI_EXT_HSM_HART_START also avoids
> the simultaneous updates to the reset context of target VCPU. Since this
> lock has been replace with vcpu->mp_state_lock, and this new lock also
> protects the vcpu->mp_state. We have to add a separate lock for
> vcpu->reset_cntx.
>
> Signed-off-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>

LGTM.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup


> ---
>  arch/riscv/include/asm/kvm_host.h | 1 +
>  arch/riscv/kvm/vcpu.c             | 6 ++++++
>  arch/riscv/kvm/vcpu_sbi_hsm.c     | 3 +++
>  3 files changed, 10 insertions(+)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 64d35a8c908c..664d1bb00368 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -211,6 +211,7 @@ struct kvm_vcpu_arch {
>
>         /* CPU context upon Guest VCPU reset */
>         struct kvm_cpu_context guest_reset_context;
> +       spinlock_t reset_cntx_lock;
>
>         /* CPU CSR context upon Guest VCPU reset */
>         struct kvm_vcpu_csr guest_reset_csr;
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 70937f71c3c4..1a2236e4c7f3 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -64,7 +64,9 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
>
>         memcpy(csr, reset_csr, sizeof(*csr));
>
> +       spin_lock(&vcpu->arch.reset_cntx_lock);
>         memcpy(cntx, reset_cntx, sizeof(*cntx));
> +       spin_unlock(&vcpu->arch.reset_cntx_lock);
>
>         kvm_riscv_vcpu_fp_reset(vcpu);
>
> @@ -121,12 +123,16 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>         spin_lock_init(&vcpu->arch.hfence_lock);
>
>         /* Setup reset state of shadow SSTATUS and HSTATUS CSRs */
> +       spin_lock_init(&vcpu->arch.reset_cntx_lock);
> +
> +       spin_lock(&vcpu->arch.reset_cntx_lock);
>         cntx = &vcpu->arch.guest_reset_context;
>         cntx->sstatus = SR_SPP | SR_SPIE;
>         cntx->hstatus = 0;
>         cntx->hstatus |= HSTATUS_VTW;
>         cntx->hstatus |= HSTATUS_SPVP;
>         cntx->hstatus |= HSTATUS_SPV;
> +       spin_unlock(&vcpu->arch.reset_cntx_lock);
>
>         if (kvm_riscv_vcpu_alloc_vector_context(vcpu, cntx))
>                 return -ENOMEM;
> diff --git a/arch/riscv/kvm/vcpu_sbi_hsm.c b/arch/riscv/kvm/vcpu_sbi_hsm.c
> index 115a6c6525fd..cc5038b90e02 100644
> --- a/arch/riscv/kvm/vcpu_sbi_hsm.c
> +++ b/arch/riscv/kvm/vcpu_sbi_hsm.c
> @@ -31,6 +31,7 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
>                 goto out;
>         }
>
> +       spin_lock(&target_vcpu->arch.reset_cntx_lock);
>         reset_cntx = &target_vcpu->arch.guest_reset_context;
>         /* start address */
>         reset_cntx->sepc = cp->a1;
> @@ -38,6 +39,8 @@ static int kvm_sbi_hsm_vcpu_start(struct kvm_vcpu *vcpu)
>         reset_cntx->a0 = target_vcpuid;
>         /* private data passed from kernel */
>         reset_cntx->a1 = cp->a2;
> +       spin_unlock(&target_vcpu->arch.reset_cntx_lock);
> +
>         kvm_make_request(KVM_REQ_VCPU_RESET, target_vcpu);
>
>         __kvm_riscv_vcpu_power_on(target_vcpu);
> --
> 2.17.1
>