[PATCH v8 16/24] x86/PCI/ACPI: Fix up PCIBIOS_MIN_MEM if value computed from e820 is invalid

[Sergei Miroshnichenko <s.miroshnichenko@yadro.com>]

The value of PCIBIOS_MIN_MEM reported by BIOS 1.3 on Supermicro H11SSL-i
via e820__setup_pci_gap():

  [mem 0xebff1000-0xfe9fffff] available for PCI devices

is only suitable for a single root complex out of four (0000:00):

  pci_bus 0000:00: root bus resource [mem 0xec000000-0xefffffff window]
  pci_bus 0000:20: root bus resource [mem 0xeb800000-0xebefffff window]
  pci_bus 0000:40: root bus resource [mem 0xeb200000-0xeb5fffff window]
  pci_bus 0000:60: root bus resource [mem 0xe8b00000-0xeaffffff window]

That makes the AMD EPYC 7251 unable to assign BARs of devices hot-added in
those three unlucky RCs (0000:20, 0000:40 and 0000:60).

If there are apertures that end below the current PCIBIOS_MIN_MEM (which is
a variable pci_mem_start on x86), adjust it to the aperture's start.

CC: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sergei Miroshnichenko <s.miroshnichenko@yadro.com>
---
 arch/x86/pci/acpi.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 948656069cdd..9eccb26d0bf3 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -299,6 +299,21 @@ static int pci_acpi_root_prepare_resources(struct acpi_pci_root_info *ci)
 	int status;
 
 	status = acpi_pci_probe_root_resources(ci);
+
+	resource_list_for_each_entry(entry, &ci->resources) {
+		struct resource *res = entry->res;
+
+		if (!(res->flags & IORESOURCE_MEM) ||
+		    res->end > pci_mem_start ||
+		    res->start == 0xa0000)
+			continue;
+
+		dev_warn(&ci->root->device->dev, "Fix up PCI start address: %lx -> %llx\n",
+			 pci_mem_start, res->start);
+
+		pci_mem_start = res->start;
+	}
+
 	if (pci_use_crs) {
 		resource_list_for_each_entry_safe(entry, tmp, &ci->resources)
 			if (resource_is_pcicfg_ioport(entry->res))
-- 
2.24.1