linux-kernel - [PATCH 4/4] iommu/vt-d: Remove commented-out code

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20230614024705.88878-5-baolu.lu@linux.intel.com>
Date:   Wed, 14 Jun 2023 10:47:05 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Joerg Roedel <joro@...tes.org>
Cc:     Yanfei Xu <yanfei.xu@...el.com>, Suhui <suhui@...china.com>,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: [PATCH 4/4] iommu/vt-d: Remove commented-out code

These lines of code were commented out when they were first added in commit
ba39592764ed ("Intel IOMMU: Intel IOMMU driver"). We do not want to restore
them because the VT-d spec has deprecated the read/write draining hit.

VT-d spec (section 11.4.2):
"
 Hardware implementation with Major Version 2 or higher (VER_REG), always
 performs required drain without software explicitly requesting a drain in
 IOTLB invalidation. This field is deprecated and hardware  will always
 report it as 1 to maintain backward compatibility with software.
"

Remove the code to make the code cleaner.

Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
Reviewed-by: Jerry Snitselaar <jsnitsel@...hat.com>
Link: https://lore.kernel.org/r/20230609060514.15154-1-baolu.lu@linux.intel.com
---
 drivers/iommu/intel/iommu.c | 10 +---------
 1 file changed, 1 insertion(+), 9 deletions(-)

diff --git a/drivers/iommu/intel/iommu.c b/drivers/iommu/intel/iommu.c
index 4c0b7424c45e..e5c111ff4dd9 100644
--- a/drivers/iommu/intel/iommu.c
+++ b/drivers/iommu/intel/iommu.c
@@ -1312,15 +1312,7 @@ static void __iommu_flush_iotlb(struct intel_iommu *iommu, u16 did,
 			iommu->name, type);
 		return;
 	}
-	/* Note: set drain read/write */
-#if 0
-	/*
-	 * This is probably to be super secure.. Looks like we can
-	 * ignore it without any impact.
-	 */
-	if (cap_read_drain(iommu->cap))
-		val |= DMA_TLB_READ_DRAIN;
-#endif
+
 	if (cap_write_drain(iommu->cap))
 		val |= DMA_TLB_WRITE_DRAIN;

-- 
2.34.1