linux-kernel - [PATCH 2/4] iommu/vt-d: Add a check for 1GB page support

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Date:   Wed, 20 Dec 2017 11:59:25 -0800
From:   Sohil Mehta <sohil.mehta@...el.com>
To:     Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>
Cc:     David Woodhouse <dwmw2@...radead.org>,
        Ashok Raj <ashok.raj@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Jacob Pan <jacob.jun.pan@...ux.intel.com>,
        Gayatri Kammela <gayatri.kammela@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Kirill Shutemov <kirill.shutemov@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>
Subject: [PATCH 2/4] iommu/vt-d: Add a check for 1GB page support

Add a check to verify IOMMU 1GB page support. If the CPU supports 1GB
pages but the IOMMU does not support it then disable SVM by not
allocating PASID tables.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
 drivers/iommu/intel-svm.c   | 4 ++++
 include/linux/intel-iommu.h | 1 +
 2 files changed, 5 insertions(+)

diff --git a/drivers/iommu/intel-svm.c b/drivers/iommu/intel-svm.c
index ed1cf7c..fcab440 100644
--- a/drivers/iommu/intel-svm.c
+++ b/drivers/iommu/intel-svm.c
@@ -41,6 +41,10 @@ int intel_svm_alloc_pasid_tables(struct intel_iommu *iommu)
 	struct page *pages;
 	int order;
 
+	if (cpu_feature_enabled(X86_FEATURE_GBPAGES) &&
+			!cap_fl1gp_support(iommu->cap))
+		return -EINVAL;
+
 	/* Start at 2 because it's defined as 2^(1+PSS) */
 	iommu->pasid_max = 2 << ecap_pss(iommu->ecap);
 
diff --git a/include/linux/intel-iommu.h b/include/linux/intel-iommu.h
index f3274d9..a56bab1 100644
--- a/include/linux/intel-iommu.h
+++ b/include/linux/intel-iommu.h
@@ -84,6 +84,7 @@
  * Decoding Capability Register
  */
 #define cap_pi_support(c)	(((c) >> 59) & 1)
+#define cap_fl1gp_support(c)	(((c) >> 56) & 1)
 #define cap_read_drain(c)	(((c) >> 55) & 1)
 #define cap_write_drain(c)	(((c) >> 54) & 1)
 #define cap_max_amask_val(c)	(((c) >> 48) & 0x3f)
-- 
2.7.4