ACK: [SRU][J][PATCH v3 0/2] amd/iommu: Fix warnings on AMD systems after booting into kdump kernel

[ivanhu]

Acked-by: Ivan Hu <ivan.hu at canonical.com>

On 2024/10/10 20:32, Ghadi Elie Rahme wrote:
> BugLink: https://bugs.launchpad.net/bugs/2080378
> 
> [impact]
> On some AMD systems, loading into a kdump kernel will show a few warnings IOMMU warnings during early boot. These warnings have not been observed yet to cause any issues but there is a fix upstream for them. Currently only focal-HWE and jammy 5.15 are affected. Newer kernel releases already have the fix. The stack traces look like the following:
> 
>      [ 9.125703] WARNING: CPU: 0 PID: 1 at drivers/iommu/amd/init.c:829 iommu_init_irq+0x2f2/0x3c0
>      [ 9.134223] Modules linked in:
>      [ 9.137283] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-107-generic #117~20.04.1-Ubuntu
>      [ 9.145716] Hardware name: <hidden>
>      [ 9.153111] RIP: 0010:iommu_init_irq+0x2f2/0x3c0
>      [ 9.157729] Code: 90 ff 85 c0 0f 84 e8 fd ff ff be 01 00 00 00 44 89 ef 89 45 94 e8 2e dc 90 ff 4c 89 e7 e8 b6 cf 90 ff 8b 45 94 e9 6c fd ff ff <0f> 0b 31 c0 e9 63 fd ff ff 0f 0b 31 c0 e9 5a fd ff ff 31 c9 48 c7
>      [ 9.176475] RSP: 0018:ffffa005000fbd00 EFLAGS: 00010202
>      [ 9.181703] RAX: 0000000000000198 RBX: ffff9335af44a000 RCX: ffffa00500100000
>      [ 9.188838] RDX: ffffa00500100000 RSI: ffff9335c05b9140 RDI: ffff9335c05b95c8
>      [ 9.195970] RBP: ffffa005000fbd70 R08: ffffffffffffffff R09: 0000000000000000
>      [ 9.203101] R10: ffffffe000000000 R11: 0000000000000025 R12: ffff9335c0468cc0
>      [ 9.210231] R13: 000000000000001a R14: ffff9335b0151600 R15: 0000000000000006
>      [ 9.217362] FS: 0000000000000000(0000) GS:ffff9336aec00000(0000) knlGS:0000000000000000
>      [ 9.225446] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>      [ 9.231185] CR2: 0000000000000000 CR3: 000002006c810000 CR4: 0000000000350ef0
>      [ 9.238318] Call Trace:
>      [ 9.240763] <TASK>
>      [ 9.242869] ? show_regs.cold+0x1a/0x1f
>      [ 9.246710] ? iommu_init_irq+0x2f2/0x3c0
>      [ 9.250722] ? __warn+0x8b/0xe0
>      [ 9.253868] ? iommu_init_irq+0x2f2/0x3c0
>      [ 9.257883] ? report_bug+0xd5/0x110
>      [ 9.261461] ? handle_bug+0x39/0x90
>      [ 9.264956] ? exc_invalid_op+0x19/0x70
>      [ 9.268794] ? asm_exc_invalid_op+0x1b/0x20
>      [ 9.272980] ? iommu_init_irq+0x2f2/0x3c0
>      [ 9.276993] ? e820__memblock_setup+0x89/0x89
>      [ 9.281353] state_next+0x3f5/0x6ba
>      [ 9.284847] ? e820__memblock_setup+0x89/0x89
>      [ 9.289206] iommu_go_to_state+0x28/0x31
>      [ 9.293131] amd_iommu_init+0x15/0x4f
>      [ 9.296797] ? e820__memblock_setup+0x89/0x89
>      [ 9.301150] pci_iommu_init+0x1a/0x48
>      [ 9.304817] do_one_initcall+0x48/0x1e0
>      [ 9.308655] kernel_init_freeable+0x284/0x2f1
>      [ 9.313016] ? rest_init+0x100/0x100
>      [ 9.316593] kernel_init+0x1b/0x150
>      [ 9.320078] ? rest_init+0x100/0x100
>      [ 9.323658] ret_from_fork+0x22/0x30
>      [ 9.327238] </TASK>
>      [ 9.329431] ---[ end trace 6113ebe8cb8ce54f ]---
> 
> The commit that fixes the issue is:
> 
> * c5e1a1eb9279 ("iommu/amd: Simplify and Consolidate Virtual APIC (AVIC) Enablement")
> 
> However another commit was also created that fixed compiler warnings introduced by the above commit:
> 
> * be280ea763f7 ("iommu/amd: Fix compile warning in init code")
> 
> [Test Plan]
> 
> 1- On a machine using an AMD CPU and running the focal-hwe or jammy 5.15 kernel, make sure kdump is configured following these steps: https://ubuntu.com/server/docs/kernel-crash-dump
> 
> 2- Trigger a kernel panic. This can be done using the command:
> 
> $ echo c > /proc/sysrq-trigger
> 
> 3- When the machine reboots, you will notice IOMMU warnings during the early phases of the boot process in dmesg.
> 
> 4- After applying the two commits and repeating step 2. No IOMMU warnings should show up anymore in dmesg.
> 
> [Fix]
> Only the first commit of the below list is required to fix the bug, but the second one is good to have to avoid compilation warnings introduced by that commit:
> 
> * c5e1a1eb9279 ("iommu/amd: Simplify and Consolidate Virtual APIC (AVIC) Enablement")
> * be280ea763f7 ("iommu/amd: Fix compile warning in init code")
> 
> [where problems could occur]
> 
> * IOMMU can fail to initialize after applying these commits on AMD systems.
> 
> * There is a chance these commits do not fix IOMMU warnings for all AMD system configurations
> 
> Joerg Roedel (1):
>    iommu/amd: Fix compile warning in init code
> 
> Suravee Suthikulpanit (1):
>    iommu/amd: Simplify and Consolidate Virtual APIC (AVIC) Enablement
> 
>   drivers/iommu/amd/init.c | 95 +++++++++++++++++++++++++---------------
>   1 file changed, 59 insertions(+), 36 deletions(-)
>