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From:   Huang Rui <ray.huang@amd.com>
To:     iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Cc:     Joerg Roedel <joro@8bytes.org>,
        Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>,
        Xiaojian Du <xiaojian.du@amd.com>,
        Huang Rui <ray.huang@amd.com>, Joerg Roedel <jroedel@suse.de>,
        stable@vger.kernel.org
Subject: [PATCH] iommu/amd: Fix iommu remap panic while amd_iommu is set to disable
Date:   Thu, 11 Mar 2021 22:28:07 +0800
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While amd_iommu is set to disable in cmd line, it will free the iommu
resources. Then the pages of rlookup table is freed as well. If that, we
have to check rlookup table in irq_remapping_select(), otherwise, it
will trigger a kernel panic below.

[    2.245855] BUG: kernel NULL pointer dereference, address: 0000000000000500
[    2.252861] #PF: supervisor read access in kernel mode
[    2.258053] #PF: error_code(0x0000) - not-present page
[    2.263247] PGD 0 P4D 0
[    2.265844] Oops: 0000 [#1] SMP NOPTI
[    2.269570] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.11.0-custom #1
[    2.276150] Hardware name: AMD Chachani-VN/Chachani-VN, BIOS VCH162755N.FD 03/04/2021
[    2.284085] RIP: 0010:irq_remapping_select+0x5c/0xb0
[    2.289107] Code: 4b 0c 48 3d 70 7c c8 8f 75 0d eb 35 48 8b 00 48 3d 70 7c c8 8f 74 2a 0f b6 50 10 39 d1 75 ed 0f b7 40 12 48 8b 15 f4 8a 3b 02 <48> 8b 14 c2 48 85 d2 74 0e b8 01 00 00 00 4c 3b a2 90 04 00 00 74
[    2.307999] RSP: 0000:ffffffff8f403d40 EFLAGS: 00010246
[    2.313285] RAX: 00000000000000a0 RBX: ffffffff8f403d98 RCX: 0000000000000021
[    2.320471] RDX: 0000000000000000 RSI: 000000000000000a RDI: ffff8cbb4006118a
[    2.327658] RBP: ffffffff8f403d50 R08: 0000000000000021 R09: 0000000000000002
[    2.334838] R10: 000000000000000a R11: f000000000000000 R12: ffff8cbb401bfe40
[    2.342022] R13: 0000000000000000 R14: ffff8cbb401be900 R15: 0000000000000000
[    2.349210] FS:  0000000000000000(0000) GS:ffff8cbd73e00000(0000) knlGS:0000000000000000
[    2.357399] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[    2.363198] CR2: 0000000000000500 CR3: 00000002dae0a000 CR4: 00000000000406b0
[    2.370382] Call Trace:
[    2.372897]  irq_find_matching_fwspec+0x48/0xd0
[    2.377489]  mp_irqdomain_create+0x7c/0x180
[    2.381736]  ? __raw_callee_save___native_queued_spin_unlock+0x15/0x23
[    2.388320]  setup_IO_APIC+0x81/0x875
[    2.392048]  ? clear_IO_APIC_pin+0xd6/0x130
[    2.396294]  ? clear_IO_APIC+0x39/0x60
[    2.400103]  apic_intr_mode_init+0x107/0x10a
[    2.404432]  x86_late_time_init+0x24/0x35
[    2.408507]  start_kernel+0x509/0x5c7
[    2.412230]  x86_64_start_reservations+0x24/0x26
[    2.416911]  x86_64_start_kernel+0x75/0x79
[    2.421068]  secondary_startup_64_no_verify+0xb0/0xbb

Fixes: a1a785b572425 ("iommu/amd: Implement select() method on remapping irqdomain")
Tested-by: Xiaojian Du <xiaojian.du@amd.com>
Signed-off-by: Huang Rui <ray.huang@amd.com>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
---
 drivers/iommu/amd/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/iommu.c b/drivers/iommu/amd/iommu.c
index f0adbc48fd17..a08e885403b7 100644
--- a/drivers/iommu/amd/iommu.c
+++ b/drivers/iommu/amd/iommu.c
@@ -3862,7 +3862,7 @@ static int irq_remapping_select(struct irq_domain *d, struct irq_fwspec *fwspec,
 	else if (x86_fwspec_is_hpet(fwspec))
 		devid = get_hpet_devid(fwspec->param[0]);
 
-	if (devid < 0)
+	if (devid < 0 || !amd_iommu_rlookup_table)
 		return 0;
 
 	iommu = amd_iommu_rlookup_table[devid];
-- 
2.25.1