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From:   "Zhang, Tina" <tina.zhang@intel.com>
To:     "Xu, Yanfei" <yanfei.xu@intel.com>,
        "dwmw2@infradead.org" <dwmw2@infradead.org>,
        "baolu.lu@linux.intel.com" <baolu.lu@linux.intel.com>,
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CC:     "iommu@lists.linux.dev" <iommu@lists.linux.dev>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "Xu, Yanfei" <yanfei.xu@intel.com>
Subject: RE: [PATCH] iommu/vt-d: Fix to flush cache of PASID directory table
Thread-Topic: [PATCH] iommu/vt-d: Fix to flush cache of PASID directory table
Thread-Index: AQHZn1m2Yu+6fSI1tEWmXm/q0t2Ghq+Mg/Aw
Date:   Thu, 15 Jun 2023 23:43:59 +0000
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Hi,

> -----Original Message-----
> From: Yanfei Xu <yanfei.xu@intel.com>
> Sent: Thursday, June 15, 2023 3:16 PM
> To: dwmw2@infradead.org; baolu.lu@linux.intel.com; joro@8bytes.org;
> will@kernel.org; robin.murphy@arm.com
> Cc: iommu@lists.linux.dev; linux-kernel@vger.kernel.org; Xu, Yanfei
> <yanfei.xu@intel.com>
> Subject: [PATCH] iommu/vt-d: Fix to flush cache of PASID directory table
>=20
> Even the PCI devices don't support pasid capability, PASID table is manda=
tory
> for a PCI device in scalable mode. However flushing cache of pasid direct=
ory
> table for these devices are not taken after pasid table is allocated as t=
he "size"
> of table is zero. Fix to assign it with a page size.
>=20
> Fixes: 194b3348bdbb ("iommu/vt-d: Fix PASID directory pointer coherency")
> Signed-off-by: Yanfei Xu <yanfei.xu@intel.com>
> ---
>  drivers/iommu/intel/pasid.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>=20
> diff --git a/drivers/iommu/intel/pasid.c b/drivers/iommu/intel/pasid.c in=
dex
> 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);
>=20
>  	size =3D max_pasid >> (PASID_PDE_SHIFT - 3);
> -	order =3D size ? get_order(size) : 0;
> +	if (!size)
> +		size =3D PAGE_SIZE;
How about merging the logic of the above few lines into this one:
size =3D 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 =3D get_order(size);
>  	pages =3D alloc_pages_node(info->iommu->node,
>  				 GFP_KERNEL | __GFP_ZERO, order);
>  	if (!pages) {
> --
> 2.34.1
>=20