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Subject[PATCH] iommu/amd: Enable swiotlb if any device supports iommu v2 and uses identity mapping
Date
We are seeing kernel panic on rtw88 probe routine because swiotlb isn't
set:
[ 252.036773] rtw_8821ce 0000:06:00.0: enabling device (0000 -> 0003)
[ 252.037084] Kernel panic - not syncing: Can not allocate SWIOTLB buffer earlier and can't now provide you with the DMA bounce buffer
[ 252.037146] CPU: 7 PID: 1174 Comm: modprobe Not tainted 5.13.0+ #39
[ 252.037175] Hardware name: HP HP ProDesk 405 G6 Small Form Factor PC/8835, BIOS S05 Ver. 02.04.00 06/03/2021
[ 252.037218] Call Trace:
[ 252.037231] dump_stack_lvl+0x4a/0x5f
[ 252.037251] dump_stack+0x10/0x12
[ 252.037267] panic+0x101/0x2e3
[ 252.037284] swiotlb_tbl_map_single.cold+0xc/0x73
[ 252.037305] ? __mod_lruvec_page_state+0x95/0xb0
[ 252.037329] ? kmalloc_large_node+0x8c/0xb0
[ 252.037348] ? __netdev_alloc_skb+0x44/0x160
[ 252.037370] swiotlb_map+0x61/0x240
[ 252.037387] ? __alloc_skb+0xed/0x1e0
[ 252.037404] dma_map_page_attrs+0x12c/0x1f0
[ 252.037422] ? __netdev_alloc_skb+0x44/0x160
[ 252.037443] rtw_pci_probe+0x30f/0x872 [rtw88_pci]
[ 252.037467] local_pci_probe+0x48/0x80
[ 252.037487] pci_device_probe+0x105/0x1c0
[ 252.037506] really_probe+0x1fe/0x3f0
[ 252.037524] __driver_probe_device+0x109/0x180
[ 252.037545] driver_probe_device+0x23/0x90
[ 252.037564] __driver_attach+0xac/0x1b0
[ 252.037582] ? __device_attach_driver+0xe0/0xe0
[ 252.037602] bus_for_each_dev+0x7e/0xc0
[ 252.037620] driver_attach+0x1e/0x20
[ 252.037637] bus_add_driver+0x135/0x1f0
[ 252.037654] driver_register+0x95/0xf0
[ 252.037672] ? 0xffffffffc0fa0000
[ 252.037687] __pci_register_driver+0x68/0x70
[ 252.037707] rtw_8821ce_driver_init+0x23/0x1000 [rtw88_8821ce]
[ 252.037734] do_one_initcall+0x48/0x1d0
[ 252.037752] ? __cond_resched+0x1a/0x50
[ 252.037771] ? kmem_cache_alloc_trace+0x29d/0x3c0
[ 252.037792] do_init_module+0x62/0x280
[ 252.037810] load_module+0x2577/0x27c0
[ 252.037862] __do_sys_finit_module+0xbf/0x120
[ 252.037877] __x64_sys_finit_module+0x1a/0x20
[ 252.037893] do_syscall_64+0x3b/0xc0
[ 252.037907] entry_SYSCALL_64_after_hwframe+0x44/0xae
[ 252.037925] RIP: 0033:0x7ff5a2f9408d
[ 252.037938] Code: 27 0d 00 0f 05 eb a9 66 0f 1f 44 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ab dd 0c 00 f7 d8 64 89 01 48
[ 252.037993] RSP: 002b:00007fffaa89dce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000139
[ 252.038017] RAX: ffffffffffffffda RBX: 000055fd4f881080 RCX: 00007ff5a2f9408d
[ 252.038039] RDX: 0000000000000000 RSI: 000055fd4f63ec02 RDI: 0000000000000009
[ 252.038063] RBP: 0000000000040000 R08: 0000000000000000 R09: 000055fd4f8885b0
[ 252.038085] R10: 0000000000000009 R11: 0000000000000246 R12: 000055fd4f63ec02
[ 252.038107] R13: 000055fd4f881120 R14: 0000000000000000 R15: 000055fd4f88e350
[ 252.038293] Kernel Offset: 0x30600000 from 0xffffffff81000000 (relocation range: 0xffffffff80000000-0xffffffffbfffffff)

Because the Realtek WiFi (PCI 06:00.0) is in the same IOMMU group as AMD
graphics (PCI 01:00.0),
[ 1.326166] pci 0000:01:00.0: Adding to iommu group 0
...
[ 1.326268] pci 0000:06:00.0: Adding to iommu group 0

And the AMD graphics supports iommu v2, so the group uses intentity
mapping based on the query from amd_iommu_def_domain_type().

However, the Realtek WiFi doesn't support 64bit DMA, so we need to
enable swiotlb, which was disabled by amd_iommu_init_dma_ops(), to make
remapping work.

Cc: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
---
drivers/iommu/amd/iommu.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index 811a49a95d04..7c5111ed5c97 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -344,6 +344,9 @@ static int iommu_init_device(struct device *dev)

iommu = amd_iommu_rlookup_table[dev_data->devid];
dev_data->iommu_v2 = iommu->is_iommu_v2;
+
+ if (dev_data->iommu_v2)
+ swiotlb = 1;
}

dev_iommu_priv_set(dev, dev_data);
--
2.31.1
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