linux-kernel - Re: [PATCH] iommu/vt-d: fix system hang on reboot -f

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Message-ID: <ba2a6295-7983-4701-8c42-797efe22ecb7@linux.intel.com>
Date: Fri, 21 Feb 2025 16:40:39 +0800
From: Ethan Zhao <haifeng.zhao@...ux.intel.com>
To: Yunhui Cui <cuiyunhui@...edance.com>, dwmw2@...radead.org,
 baolu.lu@...ux.intel.com, joro@...tes.org, will@...nel.org,
 robin.murphy@....com, iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iommu/vt-d: fix system hang on reboot -f


在 2025/2/20 18:15, Yunhui Cui 写道:
> When entering intel_iommu_shutdown, system interrupts are disabled,

System interrupts were disabled ? you mean all interrupts were disabled
when entering intel_iommu_shutdown(), perhaps it is not true, at least
for upstream latest code.

> and the reboot process might be scheduled out by down_write(). If the
> scheduled process does not yield (e.g., while(1)), the system will hang.

No NMI lockup watchdog jumping out here ?

Thanks,
Ethan

>
> Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
> ---
>   drivers/iommu/intel/iommu.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
> index cc46098f875b..76a1d83b46bf 100644
> --- a/drivers/iommu/intel/iommu.c
> +++ b/drivers/iommu/intel/iommu.c
> @@ -2871,7 +2871,8 @@ void intel_iommu_shutdown(void)
>   	if (no_iommu || dmar_disabled)
>   		return;
>   
> -	down_write(&dmar_global_lock);
> +	if (!down_write_trylock(&dmar_global_lock))
> +		return;
>   
>   	/* Disable PMRs explicitly here. */
>   	for_each_iommu(iommu, drhd)

-- 
"firm, enduring, strong, and long-lived"