linux-kernel - [PATCH] iommu: fix iommu_free() comparison of unsigned expression >= 0

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Date:   Tue, 15 Nov 2016 09:47:49 +0100
From:   Nikola Pajkovsky <npajkovsky@...e.cz>
To:     Muli Ben-Yehuda <mulix@...ix.org>, Jon Mason <jdmason@...zu.us>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [PATCH] iommu: fix iommu_free() comparison of unsigned expression >= 0

commit 8fd524b355da ("x86: Kill bad_dma_address variable") has killed
bad_dma_address variable and used instead of macro DMA_ERROR_CODE
which is always zero. Since dma_addr is unsigned, statement

   dma_addr >= DMA_ERROR_CODE

is always true, and not needed.

arch/x86/kernel/pci-calgary_64.c: In function ‘iommu_free’:
arch/x86/kernel/pci-calgary_64.c:299:2: warning: comparison of unsigned expression >= 0 is always true [-Wtype-limits]
  if (unlikely((dma_addr >= DMA_ERROR_CODE) && (dma_addr < badend))) {

Fixes: 8fd524b355da ("x86: Kill bad_dma_address variable")
Signed-off-by: Nikola Pajkovsky <npajkovsky@...e.cz>
---
 arch/x86/kernel/pci-calgary_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pci-calgary_64.c b/arch/x86/kernel/pci-calgary_64.c
index 5d400ba1349d..d47517941bbc 100644
--- a/arch/x86/kernel/pci-calgary_64.c
+++ b/arch/x86/kernel/pci-calgary_64.c
@@ -296,7 +296,7 @@ static void iommu_free(struct iommu_table *tbl, dma_addr_t dma_addr,
 
 	/* were we called with bad_dma_address? */
 	badend = DMA_ERROR_CODE + (EMERGENCY_PAGES * PAGE_SIZE);
-	if (unlikely((dma_addr >= DMA_ERROR_CODE) && (dma_addr < badend))) {
+	if (unlikely(dma_addr < badend)) {
 		WARN(1, KERN_ERR "Calgary: driver tried unmapping bad DMA "
 		       "address 0x%Lx\n", dma_addr);
 		return;
-- 
2.10.0