[PATCH AUTOSEL 6.18-5.10] iommu/amd: Add support for Hygon family 18h model 4h IOAPIC

[Sasha Levin <sashal@kernel.org>]

From: Fu Hao <fuhao@open-hieco.net>

[ Upstream commit 5beda8cadb1f072140e58b1edb7604444a42d955 ]

The SB IOAPIC is on the device 0xb from Hygon family 18h model 4h.

Signed-off-by: Fu Hao <fuhao@open-hieco.net>
Tested-by: Tingyin Duan <tingyin.duan@gmail.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---

LLM Generated explanations, may be completely bogus:

The `git log -S "No southbridge IOAPIC found"` search finished after
~8.7 minutes. The last hits were mostly unrelated merge commits; the
closest relevant one is `7d2fed1f3ce46` (irq merge for v6.17-rc1), but
pickaxe history here still doesn’t give a clean “introduced in” commit.

That doesn’t affect the backport call: the AMD-only IOAPIC check is
already in this **6.18.43** tree, and the Hygon quirk fix remains
**YES**.

 drivers/iommu/amd/init.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
index 69170146d4421..0de0791d46bef 100644
--- a/drivers/iommu/amd/init.c
+++ b/drivers/iommu/amd/init.c
@@ -3096,6 +3096,9 @@ static void __init free_iommu_resources(void)
 /* SB IOAPIC is always on this device in AMD systems */
 #define IOAPIC_SB_DEVID		((0x00 << 8) | PCI_DEVFN(0x14, 0))
 
+/* SB IOAPIC for Hygon family 18h model 4h is on the device 0xb */
+#define IOAPIC_SB_DEVID_FAM18H_M4H	((0x00 << 8) | PCI_DEVFN(0xb, 0))
+
 static bool __init check_ioapic_information(void)
 {
 	const char *fw_bug = FW_BUG;
@@ -3121,7 +3124,12 @@ static bool __init check_ioapic_information(void)
 			pr_err("%s: IOAPIC[%d] not in IVRS table\n",
 				fw_bug, id);
 			ret = false;
-		} else if (devid == IOAPIC_SB_DEVID) {
+		} else if (devid == IOAPIC_SB_DEVID ||
+			   (boot_cpu_data.x86_vendor == X86_VENDOR_HYGON &&
+			    boot_cpu_data.x86 == 0x18 &&
+			    boot_cpu_data.x86_model >= 0x4 &&
+			    boot_cpu_data.x86_model <= 0xf &&
+			    devid == IOAPIC_SB_DEVID_FAM18H_M4H)) {
 			has_sb_ioapic = true;
 			ret           = true;
 		}
-- 
2.53.0