linux-kernel - [RFC 7/7] iommu/vt-d: Always set DMA_PTE_READ if the iommu doens't support zero length reads

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Message-Id: <20190504132327.27041-8-tmurphy@arista.com>
Date:   Sat,  4 May 2019 14:23:23 +0100
From:   Tom Murphy <tmurphy@...sta.com>
To:     iommu@...ts.linux-foundation.org
Cc:     murphyt7@....ie, Tom Murphy <tmurphy@...sta.com>,
        Joerg Roedel <joro@...tes.org>,
        Will Deacon <will.deacon@....com>,
        Robin Murphy <robin.murphy@....com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Andy Gross <andy.gross@...aro.org>,
        David Brown <david.brown@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Rob Clark <robdclark@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Gerald Schaefer <gerald.schaefer@...ibm.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Marc Zyngier <marc.zyngier@....com>,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-arm-msm@...r.kernel.org,
        linux-mediatek@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-tegra@...r.kernel.org, kvm@...r.kernel.org
Subject: [RFC 7/7] iommu/vt-d: Always set DMA_PTE_READ if the iommu doens't support zero length reads

To match the dma-ops api path the DMA_PTE_READ should be set if ZLR
isn't supported in the iommu

Signed-off-by: Tom Murphy <tmurphy@...sta.com>
---
 drivers/iommu/intel-iommu.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 980fc4816d72..e78b0000056d 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4378,6 +4378,17 @@ static void intel_iommu_detach_device(struct iommu_domain *domain,
 	dmar_remove_one_dev_info(dev);
 }
 
+static bool supports_zlr(struct dmar_domain *domain)
+{
+	int i;
+
+	for_each_domain_iommu(i, domain) {
+		if (cap_zlr(g_iommus[i]->cap))
+			return true;
+	}
+	return false;
+}
+
 static int intel_iommu_map(struct iommu_domain *domain,
 			   unsigned long iova, phys_addr_t hpa,
 			   size_t size, int iommu_prot)
@@ -4391,7 +4402,7 @@ static int intel_iommu_map(struct iommu_domain *domain,
 	if (dmar_domain == si_domain && hw_pass_through)
 		return 0;
 
-	if (iommu_prot & IOMMU_READ)
+	if (iommu_prot & IOMMU_READ || !supports_zlr(dmar_domain))
 		prot |= DMA_PTE_READ;
 	if (iommu_prot & IOMMU_WRITE)
 		prot |= DMA_PTE_WRITE;
-- 
2.17.1