[3.13.y.z extended stable] Patch "iommu/arm-smmu: remove pgtable_page_{c, d}tor()" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    iommu/arm-smmu: remove pgtable_page_{c,d}tor()

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.9.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 3133646ca3b09951861de0745c87e541b496d05f Mon Sep 17 00:00:00 2001
From: Vladimir Murzin <vladimir.murzin at arm.com>
Date: Fri, 8 Aug 2014 10:31:47 +0100
Subject: iommu/arm-smmu: remove pgtable_page_{c,d}tor()

commit 93b14135cf24668b45eb57348312b627a8539bc4 upstream.

If split page table lock for PTE tables is enabled (CONFIG_SPLIT_PTLOCK_CPUS
<=NR_CPUS) pgtable_page_ctor() leads to non-atomic allocation for ptlock with
a spinlock held, resulting in:

------------[ cut here ]------------
WARNING: CPU: 0 PID: 466 at kernel/locking/lockdep.c:2742 lockdep_trace_alloc+0xd8/0xf4()
DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags))
Modules linked in:
CPU: 0 PID: 466 Comm: dma0chan0-copy0 Not tainted 3.16.0-3d47efb-clean-pl330-dma_test-ve-a15-a32-slr-m
c-on-3+ #55
[<80014748>] (unwind_backtrace) from [<80011640>] (show_stack+0x10/0x14)
[<80011640>] (show_stack) from [<802bf864>] (dump_stack+0x80/0xb4)
[<802bf864>] (dump_stack) from [<8002385c>] (warn_slowpath_common+0x64/0x88)
[<8002385c>] (warn_slowpath_common) from [<80023914>] (warn_slowpath_fmt+0x30/0x40)
[<80023914>] (warn_slowpath_fmt) from [<8005d818>] (lockdep_trace_alloc+0xd8/0xf4)
[<8005d818>] (lockdep_trace_alloc) from [<800d3d78>] (kmem_cache_alloc+0x24/0x144)
[<800d3d78>] (kmem_cache_alloc) from [<800bfae4>] (ptlock_alloc+0x18/0x2c)
[<800bfae4>] (ptlock_alloc) from [<802b1ec0>] (arm_smmu_handle_mapping+0x4c0/0x690)
[<802b1ec0>] (arm_smmu_handle_mapping) from [<802b0cd8>] (iommu_map+0xe0/0x148)
[<802b0cd8>] (iommu_map) from [<80019098>] (arm_coherent_iommu_map_page+0x160/0x278)
[<80019098>] (arm_coherent_iommu_map_page) from [<801f4d78>] (dmatest_func+0x60c/0x1098)
[<801f4d78>] (dmatest_func) from [<8003f8ac>] (kthread+0xcc/0xe8)
[<8003f8ac>] (kthread) from [<8000e868>] (ret_from_fork+0x14/0x2c)
---[ end trace ce0d27e6f434acf8 ]--

Split page tables lock is not used in the driver. In fact, page tables are
guarded with domain lock, so remove calls to pgtable_page_{c,d}tor().

Signed-off-by: Vladimir Murzin <vladimir.murzin at arm.com>
Signed-off-by: Will Deacon <will.deacon at arm.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/iommu/arm-smmu.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
index 91739bf..176c9ea 100644
--- a/drivers/iommu/arm-smmu.c
+++ b/drivers/iommu/arm-smmu.c
@@ -946,7 +946,6 @@ out_free_domain:
 static void arm_smmu_free_ptes(pmd_t *pmd)
 {
 	pgtable_t table = pmd_pgtable(*pmd);
-	pgtable_page_dtor(table);
 	__free_page(table);
 }

@@ -1231,10 +1230,6 @@ static int arm_smmu_alloc_init_pte(struct arm_smmu_device *smmu, pmd_t *pmd,
 			return -ENOMEM;

 		arm_smmu_flush_pgtable(smmu, page_address(table), PAGE_SIZE);
-		if (!pgtable_page_ctor(table)) {
-			__free_page(table);
-			return -ENOMEM;
-		}
 		pmd_populate(NULL, pmd, table);
 		arm_smmu_flush_pgtable(smmu, pmd, sizeof(*pmd));
 	}
--
1.9.1