iommu/vt-d: Work around broken RMRR firmware entries (80f7b3d1) · Commits · 戴 / test

The VT-d specification states that an RMRR entry in the DMAR table needs to specify the full path to the device. This is also how newer Linux kernels implement it. Unfortunatly older drivers just match for the target device and not the full path to the device, so that BIOS vendors implement that behavior into their BIOSes to make them work with older Linux kernels. But those RMRR entries break on newer Linux kernels. Work around this issue by adding a fall-back into the RMRR matching code to match those old RMRR entries too. Signed-off-by:

Joerg Roedel <jroedel@suse.de>

drivers/iommu/dmar.c

+19 −3

Original line number	Diff line number	Diff line
		@@ -178,17 +178,33 @@ static bool dmar_match_pci_path(struct dmar_pci_notify_info *info, int bus,
		int i;

		if (info->bus != bus)
		return false;
		goto fallback;
		if (info->level != count)
		return false;
		goto fallback;

		for (i = 0; i < count; i++) {
		if (path[i].device != info->path[i].device \|\|
		path[i].function != info->path[i].function)
		return false;
		goto fallback;
		}

		return true;

		fallback:

		if (count != 1)
		return false;

		i = info->level - 1;
		if (bus == info->path[i].bus &&
		path[0].device == info->path[i].device &&
		path[0].function == info->path[i].function) {
		pr_info(FW_BUG "RMRR entry for device %02x:%02x.%x is broken - applying workaround\n",
		bus, path[0].device, path[0].function);
		return true;
		}

		return false;
		}

		/* Return: > 0 if match found, 0 if no match found, < 0 if error happens */

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