Re: [PATCH] dmaengine: idxd: Move dma_free_coherent() out of spinlocked context

[Lijun Pan <lijun.pan@intel.com>]

On 12/11/2023 8:21 PM, Rex Zhang wrote:
> Task may be rescheduled within dma_free_coherent(). So dma_free_coherent()
> can't be called between spin_lock() and spin_unlock() to avoid Call Trace:
>      Call Trace:
>      <TASK>
>      dump_stack_lvl+0x37/0x50
>      __might_resched+0x16a/0x1c0
>      vunmap+0x2c/0x70
>      __iommu_dma_free+0x96/0x100
>      idxd_device_evl_free+0xd5/0x100 [idxd]
>      device_release_driver_internal+0x197/0x200
>      unbind_store+0xa1/0xb0
>      kernfs_fop_write_iter+0x120/0x1c0
>      vfs_write+0x2d3/0x400
>      ksys_write+0x63/0xe0
>      do_syscall_64+0x44/0xa0
>      entry_SYSCALL_64_after_hwframe+0x6e/0xd8
> Move it out of the context.
> 
> Fixes: 244da66cda35 ("dmaengine: idxd: setup event log configuration")
> Signed-off-by: Rex Zhang <rex.zhang@intel.com>
> Reviewed-by: Dave Jiang <dave.jiang@intel.com>
> Reviewed-by: Fenghua Yu <fenghua.yu@intel.com>
> ---

Reviewed-by: Lijun Pan <lijun.pan@intel.com>

>   drivers/dma/idxd/device.c | 9 ++++++++-
>   1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
> index 8f754f922217..fa0f880beae6 100644
> --- a/drivers/dma/idxd/device.c
> +++ b/drivers/dma/idxd/device.c
> @@ -802,6 +802,9 @@ static int idxd_device_evl_setup(struct idxd_device *idxd)
>   
>   static void idxd_device_evl_free(struct idxd_device *idxd)
>   {
> +	void *evl_log;
> +	unsigned int evl_log_size;
> +	dma_addr_t evl_dma;
>   	union gencfg_reg gencfg;
>   	union genctrl_reg genctrl;
>   	struct device *dev = &idxd->pdev->dev;
> @@ -822,11 +825,15 @@ static void idxd_device_evl_free(struct idxd_device *idxd)
>   	iowrite64(0, idxd->reg_base + IDXD_EVLCFG_OFFSET);
>   	iowrite64(0, idxd->reg_base + IDXD_EVLCFG_OFFSET + 8);
>   
> -	dma_free_coherent(dev, evl->log_size, evl->log, evl->dma);
>   	bitmap_free(evl->bmap);
> +	evl_log = evl->log;
> +	evl_log_size = evl->log_size;
> +	evl_dma = evl->dma;
>   	evl->log = NULL;
>   	evl->size = IDXD_EVL_SIZE_MIN;
>   	spin_unlock(&evl->lock);
> +
> +	dma_free_coherent(dev, evl_log_size, evl_log, evl_dma);
>   }
>   
>   static void idxd_group_config_write(struct idxd_group *group)