RE: [PATCH] iommu/vt-d: Fix to flush cache of PASID directory table

[Zhang, Tina]

Hi,

> -----Original Message-----
> From: Yanfei Xu <yanfei.xu@xxxxxxxxx>
> Sent: Thursday, June 15, 2023 3:16 PM
> To: dwmw2@xxxxxxxxxxxxx; baolu.lu@xxxxxxxxxxxxxxx; joro@xxxxxxxxxx;
> will@xxxxxxxxxx; robin.murphy@xxxxxxx
> Cc: iommu@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; Xu, Yanfei
> <yanfei.xu@xxxxxxxxx>
> Subject: [PATCH] iommu/vt-d: Fix to flush cache of PASID directory table
> 
> Even the PCI devices don't support pasid capability, PASID table is mandatory
> for a PCI device in scalable mode. However flushing cache of pasid directory
> table for these devices are not taken after pasid table is allocated as the "size"
> of table is zero. Fix to assign it with a page size.
> 
> Fixes: 194b3348bdbb ("iommu/vt-d: Fix PASID directory pointer coherency")
> Signed-off-by: Yanfei Xu <yanfei.xu@xxxxxxxxx>
> ---
>  drivers/iommu/intel/pasid.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c index
> c5d479770e12..bde7df055865 100644
> --- a/drivers/iommu/intel/pasid.c
> +++ b/drivers/iommu/intel/pasid.c
> @@ -115,7 +115,9 @@ int intel_pasid_alloc_table(struct device *dev)
>  				  intel_pasid_max_id);
> 
>  	size = max_pasid >> (PASID_PDE_SHIFT - 3);
> -	order = size ? get_order(size) : 0;
> +	if (!size)
> +		size = PAGE_SIZE;
How about merging the logic of the above few lines into this one:
size = info->pasid_supported ? max_pasid >> (PASID_PDE_SHIFT - 3) : PAGE_SIZE;

Though the logic is about the same, the suggested one seems more intuitive.

Regards,
-Tina

> +	order = get_order(size);
>  	pages = alloc_pages_node(info->iommu->node,
>  				 GFP_KERNEL | __GFP_ZERO, order);
>  	if (!pages) {
> --
> 2.34.1
>