RISCV: KVM: use raw_spinlock for critical section in imsic

[PATCH] RISCV: KVM: use raw_spinlock for critical section in imsic

Posted by Cyan Yang 2 months, 1 week ago

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@sifive.com>
Reviewed-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
---
 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)

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

Posted by Anup Patel 1 month, 2 weeks ago

On Thu, Sep 19, 2024 at 9:32 PM Cyan Yang <cyan.yang@sifive.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@sifive.com>
> Reviewed-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>

LGTM.

Reviewed-by: Anup Patel <anup@brainfault.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)
>