linux-kernel - Re: [PATCH] RISCV: KVM: use raw_spinlock for critical section in imsic

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Message-ID: <CAAhSdy3x680G2cXqam0uc1kAAg_Cd1tFhBVygOrLZ0bL9ztDBg@mail.gmail.com>
Date: Tue, 15 Oct 2024 12:15:04 +0530
From: Anup Patel <anup@...infault.org>
To: Cyan Yang <cyan.yang@...ive.com>
Cc: atishp@...shpatra.org, paul.walmsley@...ive.com, palmer@...belt.com, 
	aou@...s.berkeley.edu, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	Yong-Xuan Wang <yongxuan.wang@...ive.com>
Subject: Re: [PATCH] RISCV: KVM: use raw_spinlock for critical section in imsic

On Thu, Sep 19, 2024 at 9:32 PM Cyan Yang <cyan.yang@...ive.com> wrote:
>
> For the external interrupt updating procedure in imsic, there was a
> spinlock to protect it already. But since it should not be preempted in
> any cases, we should turn to use raw_spinlock to prevent any preemption
> in case PREEMPT_RT was enabled.
>
> Signed-off-by: Cyan Yang <cyan.yang@...ive.com>
> Reviewed-by: Yong-Xuan Wang <yongxuan.wang@...ive.com>

LGTM.

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

Regards,
Anup

> ---
>  arch/riscv/kvm/aia_imsic.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kvm/aia_imsic.c b/arch/riscv/kvm/aia_imsic.c
> index 0a1e85932..a8085cd82 100644
> --- a/arch/riscv/kvm/aia_imsic.c
> +++ b/arch/riscv/kvm/aia_imsic.c
> @@ -55,7 +55,7 @@ struct imsic {
>         /* IMSIC SW-file */
>         struct imsic_mrif *swfile;
>         phys_addr_t swfile_pa;
> -       spinlock_t swfile_extirq_lock;
> +       raw_spinlock_t swfile_extirq_lock;
>  };
>
>  #define imsic_vs_csr_read(__c)                 \
> @@ -622,7 +622,7 @@ static void imsic_swfile_extirq_update(struct kvm_vcpu *vcpu)
>          * interruptions between reading topei and updating pending status.
>          */
>
> -       spin_lock_irqsave(&imsic->swfile_extirq_lock, flags);
> +       raw_spin_lock_irqsave(&imsic->swfile_extirq_lock, flags);
>
>         if (imsic_mrif_atomic_read(mrif, &mrif->eidelivery) &&
>             imsic_mrif_topei(mrif, imsic->nr_eix, imsic->nr_msis))
> @@ -630,7 +630,7 @@ static void imsic_swfile_extirq_update(struct kvm_vcpu *vcpu)
>         else
>                 kvm_riscv_vcpu_unset_interrupt(vcpu, IRQ_VS_EXT);
>
> -       spin_unlock_irqrestore(&imsic->swfile_extirq_lock, flags);
> +       raw_spin_unlock_irqrestore(&imsic->swfile_extirq_lock, flags);
>  }
>
>  static void imsic_swfile_read(struct kvm_vcpu *vcpu, bool clear,
> @@ -1051,7 +1051,7 @@ int kvm_riscv_vcpu_aia_imsic_init(struct kvm_vcpu *vcpu)
>         }
>         imsic->swfile = page_to_virt(swfile_page);
>         imsic->swfile_pa = page_to_phys(swfile_page);
> -       spin_lock_init(&imsic->swfile_extirq_lock);
> +       raw_spin_lock_init(&imsic->swfile_extirq_lock);
>
>         /* Setup IO device */
>         kvm_iodevice_init(&imsic->iodev, &imsic_iodoev_ops);
> --
> 2.39.5 (Apple Git-154)
>