netdev - RE: [PATCH 7/8] iommu/intel: Support the gfp argument to the map

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Date:   Tue, 17 Jan 2023 03:38:51 +0000
From:   "Tian, Kevin" <kevin.tian@...el.com>
To:     Jason Gunthorpe <jgg@...dia.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Robin Murphy <robin.murphy@....com>
CC:     Alex Williamson <alex.williamson@...hat.com>,
        "ath10k@...ts.infradead.org" <ath10k@...ts.infradead.org>,
        "ath11k@...ts.infradead.org" <ath11k@...ts.infradead.org>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "iommu@...ts.linux.dev" <iommu@...ts.linux.dev>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-arm-msm@...r.kernel.org" <linux-arm-msm@...r.kernel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
        "linux-remoteproc@...r.kernel.org" <linux-remoteproc@...r.kernel.org>,
        "linux-s390@...r.kernel.org" <linux-s390@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
        "linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "nouveau@...ts.freedesktop.org" <nouveau@...ts.freedesktop.org>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>
Subject: RE: [PATCH 7/8] iommu/intel: Support the gfp argument to the
 map_pages op

> From: Jason Gunthorpe <jgg@...dia.com>
> Sent: Saturday, January 7, 2023 12:43 AM
> 
> @@ -2368,7 +2372,7 @@ static int iommu_domain_identity_map(struct
> dmar_domain *domain,
> 
>  	return __domain_mapping(domain, first_vpfn,
>  				first_vpfn, last_vpfn - first_vpfn + 1,
> -				DMA_PTE_READ|DMA_PTE_WRITE);
> +				DMA_PTE_READ|DMA_PTE_WRITE,
> GFP_KERNEL);
>  }

Baolu, can you help confirm whether switching from GFP_ATOMIC to
GFP_KERNEL is OK in this path? it looks fine to me in a quick glance
but want to be conservative here.

> @@ -4333,7 +4337,8 @@ static size_t intel_iommu_unmap(struct
> iommu_domain *domain,
> 
>  	/* Cope with horrid API which requires us to unmap more than the
>  	   size argument if it happens to be a large-page mapping. */
> -	BUG_ON(!pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level));
> +	BUG_ON(!pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level,
> +			       GFP_ATOMIC));

with level==0 it implies it's only lookup w/o pgtable allocation. From this
angle it reads better to use a more relaxed gfp e.g. GFP_KERNEL here.

> @@ -4392,7 +4397,8 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct iommu_domain *domain,
>  	int level = 0;
>  	u64 phys = 0;
> 
> -	pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level);
> +	pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level,
> +			     GFP_ATOMIC);

ditto