Re: [PATCH] iommu/mediatek: Fix crash on isr after kexec()

["Yong Wu (吴勇)" <Yong.Wu@mediatek.com>]

On Fri, 2022-11-25 at 17:28 +0100, Ricardo Ribalda wrote:
> If the system is rebooted via isr(), the IRQ handler might be
> triggerd
> before the domain is initialized. Resulting on an invalid memory
> access
> error.
> 
> Fix:
> [    0.500930] Unable to handle kernel read from unreadable memory at
> virtual address 0000000000000070
> [    0.501166] Call trace:
> [    0.501174]  report_iommu_fault+0x28/0xfc
> [    0.501180]  mtk_iommu_isr+0x10c/0x1c0
> 
> Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
> ---
> To: Yong Wu <yong.wu@mediatek.com>
> To: Joerg Roedel <joro@8bytes.org>
> To: Will Deacon <will@kernel.org>
> To: Robin Murphy <robin.murphy@arm.com>
> To: Matthias Brugger <matthias.bgg@gmail.com>
> Cc: iommu@lists.linux.dev
> Cc: linux-mediatek@lists.infradead.org
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> ---
>  drivers/iommu/mtk_iommu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
> index 2ab2ecfe01f8..17f6be5a5097 100644
> --- a/drivers/iommu/mtk_iommu.c
> +++ b/drivers/iommu/mtk_iommu.c
> @@ -454,7 +454,7 @@ static irqreturn_t mtk_iommu_isr(int irq, void
> *dev_id)
>  		fault_larb = data->plat_data-
> >larbid_remap[fault_larb][sub_comm];
>  	}
>  
> -	if (report_iommu_fault(&dom->domain, bank->parent_dev,
> fault_iova,
> +	if (dom && report_iommu_fault(&dom->domain, bank->parent_dev,
> fault_iova,


Which SoC does this issue happen? Does this issue is happened in the 
upstream kernel or the downstream kernel? 

Normally each port enable the iommu defaultly. Let's print the error
log even though "dom" is null to check which port fail here. then
analyse the port's behavior.

if (!dom || report_iommu_fault(xx))
     dev_err_ratelimited(xx)

>  			       write ? IOMMU_FAULT_WRITE :
> IOMMU_FAULT_READ)) {
>  		dev_err_ratelimited(
>  			bank->parent_dev,
> 
> ---
> base-commit: 4312098baf37ee17a8350725e6e0d0e8590252d4
> change-id: 20221125-mtk-iommu-13023f971298
> 
> Best regards,