x86/pci: Reword ECAM EfiMemoryMappedIO logging to avoid 'reserved'

fd3a8cf ("x86/pci: Treat EfiMemoryMappedIO as reservation of ECAM
space") added the concept of using the EFI memory map to help decide
whether ECAM space mentioned in the MCFG table is valid.

Unfortunately it described that EfiMemoryMappedIO space as "reserved", but
it is actually not *reserved* by the EFI memory map.  EfiMemoryMappedIO
only means the firmware requested that the OS map this space for use by
firmware runtime services.

Change the dmesg logging to describe it as simply "EfiMemoryMappedIO", not
as "reserved as EfiMemoryMappedIO".  A previous commit actually *does*
reserve the space if ACPI PNP0C01/02 devices haven't done so:

  - PCI: ECAM at [mem 0xe0000000-0xefffffff] reserved as EfiMemoryMappedIO
  + PCI: ECAM at [mem 0xe0000000-0xefffffff] is EfiMemoryMappedIO; assuming valid
    PCI: ECAM [mem 0xe0000000-0xefffffff] reserved to work around lack of ACPI motherboard _CRS

Link: https://lore.kernel.org/r/20231121183643.249006-3-helgaas@kernel.org
Tested-by: Tomasz Pala <gotar@polanet.pl>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

Author: bjorn-helgaas

arch/x86/pci/mmconfig-shared.c

@@ -443,9 +443,11 @@ static bool is_acpi_reserved(u64 start, u64 end, enum e820_type not_used)
 	return mcfg_res.flags;
 }
 
-static bool is_efi_mmio(u64 start, u64 end, enum e820_type not_used)
+static bool is_efi_mmio(struct resource *res)
 {
 #ifdef CONFIG_EFI
+	u64 start = res->start;
+	u64 end = res->start + resource_size(res);
 	efi_memory_desc_t *md;
 	u64 size, mmio_start, mmio_end;
 
@@ -455,11 +457,6 @@ static bool is_efi_mmio(u64 start, u64 end, enum e820_type not_used)
 			mmio_start = md->phys_addr;
 			mmio_end = mmio_start + size;
 
-			/*
-			 * N.B. Caller supplies (start, start + size),
-			 * so to match, mmio_end is the first address
-			 * *past* the EFI_MEMORY_MAPPED_IO area.
-			 */
 			if (mmio_start <= start && end <= mmio_end)
 				return true;
 		}
@@ -543,8 +540,9 @@ pci_mmcfg_check_reserved(struct device *dev, struct pci_mmcfg_region *cfg, int e
 			       "ACPI motherboard resources\n",
 			       &cfg->res);
 
-		if (is_mmconf_reserved(is_efi_mmio, cfg, dev,
-				       "EfiMemoryMappedIO")) {
+		if (is_efi_mmio(&cfg->res)) {
+			pr_info("ECAM %pR is EfiMemoryMappedIO; assuming valid\n",
+				&cfg->res);
 			conflict = insert_resource_conflict(&iomem_resource,
 							    &cfg->res);
 			if (conflict)