linux-kernel - Re: [PATCH] Fix bug in iommu_context_addr: Always get pointer to lower extended-context-table

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Date:	Tue, 25 Aug 2015 10:59:37 +0200
From:	"joro@...tes.org" <joro@...tes.org>
To:	"Xiao, Nan (Nan@...ervers-Core-OE-PSC)" <nan.xiao@...com>
Cc:	"dwmw2@...radead.org" <dwmw2@...radead.org>,
	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Fix bug in iommu_context_addr: Always get pointer to
 lower extended-context-table

On Tue, Aug 25, 2015 at 08:46:27AM +0000, Xiao, Nan (Nan@...ervers-Core-OE-PSC) wrote:
> Yes, your patch is simple and better!

Okay, I queued this patch to my x86/vt-d branch:

>From 03932776424a799c3f065a69e98076a78530288b Mon Sep 17 00:00:00 2001
From: Joerg Roedel <jroedel@...e.de>
Date: Tue, 25 Aug 2015 10:54:28 +0200
Subject: [PATCH] iommu/vt-d: Really use upper context table when necessary

There is a bug in iommu_context_addr() which will always use
the lower context table, event when the upper context table
needs to be used. Fix this issue.

Fixes: 03ecc32c5274 ("iommu/vt-d: support extended root and context entries")
Reported-by: Xiao, Nan <nan.xiao@...com>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
---
 drivers/iommu/intel-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index a85077d..63daf1b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -803,6 +803,7 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
 	struct context_entry *context;
 	u64 *entry;
 
+	entry = &root->lo;
 	if (ecs_enabled(iommu)) {
 		if (devfn >= 0x80) {
 			devfn -= 0x80;
@@ -810,7 +811,6 @@ static inline struct context_entry *iommu_context_addr(struct intel_iommu *iommu
 		}
 		devfn *= 2;
 	}
-	entry = &root->lo;
 	if (*entry & 1)
 		context = phys_to_virt(*entry & VTD_PAGE_MASK);
 	else {
-- 
1.8.4.5

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