linux-kernel - [PATCH 3.16 038/157] iommu/vt-d: Check capability before disabling protected memory

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Message-ID: <lsq.1565469607.357977088@decadent.org.uk>
Date:   Sat, 10 Aug 2019 21:40:07 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Ashok Raj" <ashok.raj@...el.com>,
        "Joerg Roedel" <jroedel@...e.de>, "mark gross" <mgross@...el.com>,
        "Lu Baolu" <baolu.lu@...ux.intel.com>,
        "Jacob Pan" <jacob.jun.pan@...ux.intel.com>
Subject: [PATCH 3.16 038/157] iommu/vt-d: Check capability before
 disabling protected memory

3.16.72-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Lu Baolu <baolu.lu@...ux.intel.com>

commit 5bb71fc790a88d063507dc5d445ab8b14e845591 upstream.

The spec states in 10.4.16 that the Protected Memory Enable
Register should be treated as read-only for implementations
not supporting protected memory regions (PLMR and PHMR fields
reported as Clear in the Capability register).

Cc: Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc: mark gross <mgross@...el.com>
Suggested-by: Ashok Raj <ashok.raj@...el.com>
Fixes: f8bab73515ca5 ("intel-iommu: PMEN support")
Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/iommu/intel-iommu.c | 3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -1394,6 +1394,9 @@ static void iommu_disable_protect_mem_re
 	u32 pmen;
 	unsigned long flags;
 
+	if (!cap_plmr(iommu->cap) && !cap_phmr(iommu->cap))
+		return;
+
 	raw_spin_lock_irqsave(&iommu->register_lock, flags);
 	pmen = readl(iommu->reg + DMAR_PMEN_REG);
 	pmen &= ~DMA_PMEN_EPM;