linux-kernel - [PATCH v2 4/8] iommu/vt-d: Reserve RID

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Message-Id: <20230327232138.1490712-5-jacob.jun.pan@linux.intel.com>
Date:   Mon, 27 Mar 2023 16:21:34 -0700
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     LKML <linux-kernel@...r.kernel.org>, iommu@...ts.linux.dev,
        Jason Gunthorpe <jgg@...dia.com>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, dmaengine@...r.kernel.org,
        vkoul@...nel.org
Cc:     "Robin Murphy" <robin.murphy@....com>,
        "Will Deacon" <will@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, Yi Liu <yi.l.liu@...el.com>,
        "Yu, Fenghua" <fenghua.yu@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        "Zanussi, Tom" <tom.zanussi@...el.com>,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH v2 4/8] iommu/vt-d: Reserve RID_PASID from global SVA PASID space

On VT-d platforms, RID_PASID is used for DMA request without PASID. We
should not treat RID_PASID special instead let it be allocated from the
global SVA PASID number space.

Consequently, for devices also do DMA with PASID, drivers will not worry
about conflicts when it comes to allocating PASIDs for in-kernel DMA.

Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
---
 drivers/iommu/intel/iommu.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 9f737ef55463..61c06f7ad8f7 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -3956,6 +3956,10 @@ int __init intel_iommu_init(void)
 
 	intel_iommu_enabled = 1;
 
+#ifdef CONFIG_INTEL_IOMMU_SVM
+	/* Reserved RID_PASID from the global namespace for legacy DMA */
+	iommu_sva_reserve_pasid(PASID_RID2PASID, PASID_RID2PASID);
+#endif
 	return 0;
 
 out_free_dmar:
-- 
2.25.1