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Subject[PATCH -next] iommu/amd: fix a warning in increase_address_space
Date
After the commit 754265bcab78 ("iommu/amd: Fix race in
increase_address_space()"), it could still possible trigger a race
condition under some heavy memory pressure below. The race to trigger a
warning is,

CPU0: CPU1:
in alloc_pte(): in increase_address_space():
while (address > PM_LEVEL_SIZE(domain->mode)) [1]

spin_lock_irqsave(&domain->lock
domain->mode += 1;
spin_unlock_irqrestore(&domain->lock

in increase_address_space():
spin_lock_irqsave(&domain->lock
if (WARN_ON_ONCE(domain->mode == PAGE_MODE_6_LEVEL))

[1] domain->mode = 5

It is unclear the triggering of the warning is the root cause of the
smartpqi offline yet, but let's fix it first by lifting the locking.

WARNING: CPU: 57 PID: 124314 at drivers/iommu/amd_iommu.c:1474
iommu_map_page+0x718/0x7e0
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec0000 flags=0x0010]
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec1000 flags=0x0010]
CPU: 57 PID: 124314 Comm: oom01 Tainted: G O
Hardware name: HPE ProLiant DL385 Gen10/ProLiant DL385 Gen10, BIOS A40
07/10/2019
RIP: 0010:iommu_map_page+0x718/0x7e0
Code: 88 a5 70 ff ff ff e9 5d fa ff ff 48 8b b5 70 ff ff ff 4c 89 ef e8
08 32 2f 00 41 80 fc 01 0f 87 b7 3d 00 00 41 83 e4 01 eb be <0f> 0b 48
8b b5 70 ff ff ff 4c 89 ef e8 e7 31 2f 00 eb dd 0f 0b 48
RSP: 0018:ffff888da4816cb8 EFLAGS: 00010046
RAX: 0000000000000000 RBX: ffff8885fe689000 RCX: ffffffff96f4a6c4
RDX: 0000000000000007 RSI: dffffc0000000000 RDI: ffff8885fe689124
RBP: ffff888da4816da8 R08: ffffed10bfcd120e R09: ffffed10bfcd120e
R10: ffffed10bfcd120d R11: ffff8885fe68906b R12: 0000000000000000
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec1a00 flags=0x0010]
R13: ffff8885fe689068 R14: ffff8885fe689124 R15: 0000000000000000
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec1e00 flags=0x0010]
FS: 00007f29722ba700(0000) GS:ffff88902f880000(0000)
knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f27f82d8000 CR3: 000000102ed9c000 CR4: 00000000003406e0
Call Trace:
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec2000 flags=0x0010]
map_sg+0x1ce/0x2f0
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec2400 flags=0x0010]
scsi_dma_map+0xd7/0x160
pqi_raid_submit_scsi_cmd_with_io_request+0x1b8/0x420 [smartpqi]
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec2800 flags=0x0010]
pqi_scsi_queue_command+0x8ab/0xe00 [smartpqi]
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec2c00 flags=0x0010]
scsi_queue_rq+0xd19/0x1360
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec3000 flags=0x0010]
__blk_mq_try_issue_directly+0x295/0x3f0
smartpqi 0000:23:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0000
address=0xffffffffffec3400 flags=0x0010]
AMD-Vi: Event logged [IO_PAGE_FAULT device=23:00.0 domain=0x0000
address=0xffffffffffec3800 flags=0x0010]
blk_mq_request_issue_directly+0xb5/0x100
AMD-Vi: Event logged [IO_PAGE_FAULT device=23:00.0 domain=0x0000
address=0xffffffffffec3c00 flags=0x0010]
blk_mq_try_issue_list_directly+0xa9/0x160
blk_mq_sched_insert_requests+0x228/0x380
blk_mq_flush_plug_list+0x448/0x7e0
blk_flush_plug_list+0x1eb/0x230
blk_finish_plug+0x43/0x5d
shrink_node_memcg+0x9c5/0x1550
smartpqi 0000:23:00.0: controller is offline: status code 0x14803
smartpqi 0000:23:00.0: controller offline

Fixes: 754265bcab78 ("iommu/amd: Fix race in increase_address_space()")
Signed-off-by: Qian Cai <cai@lca.pw>
---

BTW, Joerg, this line from the commit "iommu/amd: Remove domain->updated" looks
suspicious. Not sure what the purpose of it.

*updated = increase_address_space(domain, gfp) || *updated;

drivers/iommu/amd_iommu.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 2369b8af81f3..a5754068aa29 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -1465,12 +1465,9 @@ static void free_pagetable(struct protection_domain *domain)
static bool increase_address_space(struct protection_domain *domain,
gfp_t gfp)
{
- unsigned long flags;
bool ret = false;
u64 *pte;

- spin_lock_irqsave(&domain->lock, flags);
-
if (WARN_ON_ONCE(domain->mode == PAGE_MODE_6_LEVEL))
/* address space already 64 bit large */
goto out;
@@ -1487,8 +1484,6 @@ static bool increase_address_space(struct protection_domain *domain,
ret = true;

out:
- spin_unlock_irqrestore(&domain->lock, flags);
-
return ret;
}

@@ -1499,14 +1494,19 @@ static u64 *alloc_pte(struct protection_domain *domain,
gfp_t gfp,
bool *updated)
{
+ unsigned long flags;
int level, end_lvl;
u64 *pte, *page;

BUG_ON(!is_power_of_2(page_size));

+ spin_lock_irqsave(&domain->lock, flags);
+
while (address > PM_LEVEL_SIZE(domain->mode))
*updated = increase_address_space(domain, gfp) || *updated;

+ spin_unlock_irqrestore(&domain->lock, flags);
+
level = domain->mode - 1;
pte = &domain->pt_root[PM_LEVEL_INDEX(level, address)];
address = PAGE_SIZE_ALIGN(address, page_size);
--
1.8.3.1
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