linux-kernel - [PATCH] iommu/amd: silence warnings under memory pressure

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Message-Id: <1567028383-29325-1-git-send-email-cai@lca.pw>
Date:   Wed, 28 Aug 2019 17:39:43 -0400
From:   Qian Cai <cai@....pw>
To:     jroedel@...e.de
Cc:     iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Qian Cai <cai@....pw>
Subject: [PATCH] iommu/amd: silence warnings under memory pressure

When running heavy memory pressure workloads, the system is throwing
endless warnings,

smartpqi 0000:23:00.0: AMD-Vi: IOMMU mapping error in map_sg (io-pages:
5 reason: -12)
Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40
07/10/2019
swapper/10: page allocation failure: order:0, mode:0xa20(GFP_ATOMIC),
nodemask=(null),cpuset=/,mems_allowed=0,4
Call Trace:
 <IRQ>
 dump_stack+0x62/0x9a
 warn_alloc.cold.43+0x8a/0x148
 __alloc_pages_nodemask+0x1a5c/0x1bb0
 get_zeroed_page+0x16/0x20
 iommu_map_page+0x477/0x540
 map_sg+0x1ce/0x2f0
 scsi_dma_map+0xc6/0x160
 pqi_raid_submit_scsi_cmd_with_io_request+0x1c3/0x470 [smartpqi]
 do_IRQ+0x81/0x170
 common_interrupt+0xf/0xf
 </IRQ>

because the allocation could fail from iommu_map_page(), and the volume
of this call could be huge which may generate a lot of serial console
output and cosumes all CPUs.

Fix it by silencing the warning in this call site, and there is still a
dev_err() later to notify the failure.

Signed-off-by: Qian Cai <cai@....pw>
---
 drivers/iommu/amd_iommu.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index b607a92791d3..19eef1edf8ed 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2547,7 +2547,9 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
 
 			bus_addr  = address + s->dma_address + (j << PAGE_SHIFT);
 			phys_addr = (sg_phys(s) & PAGE_MASK) + (j << PAGE_SHIFT);
-			ret = iommu_map_page(domain, bus_addr, phys_addr, PAGE_SIZE, prot, GFP_ATOMIC);
+			ret = iommu_map_page(domain, bus_addr, phys_addr,
+					     PAGE_SIZE, prot,
+					     GFP_ATOMIC | __GFP_NOWARN);
 			if (ret)
 				goto out_unmap;
 
-- 
1.8.3.1