linux-kernel - Re: [PATCH v3 9/9] LoongArch: KVM: INTC: Add address alignment check

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Message-ID: <CAAhV-H6Eru5e6+_i+4DY9qwshibY43hjbS-QC-fhLD04-4mOGw@mail.gmail.com>
Date: Thu, 19 Jun 2025 16:47:22 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Bibo Mao <maobibo@...ngson.cn>
Cc: Tianrui Zhao <zhaotianrui@...ngson.cn>, Xianglai Li <lixianglai@...ngson.cn>, kvm@...r.kernel.org, 
	loongarch@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 9/9] LoongArch: KVM: INTC: Add address alignment check

Hi, Bibo,

On Wed, Jun 11, 2025 at 9:51 AM Bibo Mao <maobibo@...ngson.cn> wrote:
>
> IOCSR instruction supports 1/2/4/8 bytes access, the address should
> be naturally aligned with its access size. Here address alignment
> check is added in eiointc kernel emulation.
>
> At the same time len must be 1/2/4/8 bytes from iocsr exit emulation
> function kvm_emu_iocsr(), remove the default case in switch case
> statements.
Robust code doesn't depend its callers do things right, so I suggest
keeping the default case, which means we just add the alignment check
here.

And I think this patch should also Cc stable and add a Fixes tag.


Huacai

>
> Signed-off-by: Bibo Mao <maobibo@...ngson.cn>
> ---
>  arch/loongarch/kvm/intc/eiointc.c | 21 +++++++++++++--------
>  1 file changed, 13 insertions(+), 8 deletions(-)
>
> diff --git a/arch/loongarch/kvm/intc/eiointc.c b/arch/loongarch/kvm/intc/eiointc.c
> index 8b0d9376eb54..4e9d12300cc4 100644
> --- a/arch/loongarch/kvm/intc/eiointc.c
> +++ b/arch/loongarch/kvm/intc/eiointc.c
> @@ -311,6 +311,12 @@ static int kvm_eiointc_read(struct kvm_vcpu *vcpu,
>                 return -EINVAL;
>         }
>
> +       /* len must be 1/2/4/8 from function kvm_emu_iocsr() */
> +       if (addr & (len - 1)) {
> +               kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
> +               return -EINVAL;
> +       }
> +
>         vcpu->stat.eiointc_read_exits++;
>         spin_lock_irqsave(&eiointc->lock, flags);
>         switch (len) {
> @@ -323,12 +329,9 @@ static int kvm_eiointc_read(struct kvm_vcpu *vcpu,
>         case 4:
>                 ret = loongarch_eiointc_readl(vcpu, eiointc, addr, val);
>                 break;
> -       case 8:
> +       default:
>                 ret = loongarch_eiointc_readq(vcpu, eiointc, addr, val);
>                 break;
> -       default:
> -               WARN_ONCE(1, "%s: Abnormal address access: addr 0x%llx, size %d\n",
> -                                               __func__, addr, len);
>         }
>         spin_unlock_irqrestore(&eiointc->lock, flags);
>
> @@ -682,6 +685,11 @@ static int kvm_eiointc_write(struct kvm_vcpu *vcpu,
>                 return -EINVAL;
>         }
>
> +       if (addr & (len - 1)) {
> +               kvm_err("%s: eiointc not aligned addr %llx len %d\n", __func__, addr, len);
> +               return -EINVAL;
> +       }
> +
>         vcpu->stat.eiointc_write_exits++;
>         spin_lock_irqsave(&eiointc->lock, flags);
>         switch (len) {
> @@ -694,12 +702,9 @@ static int kvm_eiointc_write(struct kvm_vcpu *vcpu,
>         case 4:
>                 ret = loongarch_eiointc_writel(vcpu, eiointc, addr, val);
>                 break;
> -       case 8:
> +       default:
>                 ret = loongarch_eiointc_writeq(vcpu, eiointc, addr, val);
>                 break;
> -       default:
> -               WARN_ONCE(1, "%s: Abnormal address access: addr 0x%llx, size %d\n",
> -                                               __func__, addr, len);
>         }
>         spin_unlock_irqrestore(&eiointc->lock, flags);
>
> --
> 2.39.3
>