[PATCH 2/3] x86/PCI: Log host bridge window clipping for E820 regions

[Bjorn Helgaas <helgaas@kernel.org>]

From: Bjorn Helgaas <bhelgaas@google.com>

ACPI firmware advertises PCI host bridge resources via PNP0A03 _CRS
methods.  Some BIOSes include non-window address space in _CRS, and if we
allocate that non-window space for PCI devices, they don't work.

4dc2287c1805 ("x86: avoid E820 regions when allocating address space")
works around this issue by clipping out any regions mentioned in the E820
table in the allocate_resource() path, but the implementation has several
issues:

  - The clipping is done for *all* allocations, not just those for PCI
    address space,

  - The clipping is done at each allocation instead of being done once when
    setting up the host bridge windows, and

  - The host bridge windows logged in dmesg do not reflect the clipping,
    and in fact there is *no* indication in dmesg, which complicates
    debugging.

Rework the implementation so we only clip PCI host bridge windows, we do it
once when setting them up, we a log message when a window is clipped, and
we reflect the clip when printing the host bridge windows.

I intend this only to improve the logging, not to fix any issues.

Example output changes:

    BIOS-e820: [mem 0x00000000b0000000-0x00000000c00fffff] reserved
  + acpi PNP0A08:00: clipped [mem 0xc0000000-0xfebfffff window] to [mem 0xc0100000-0xfebfffff window] for e820 entry [mem 0xb0000000-0xc00fffff]
  - pci_bus 0000:00: root bus resource [mem 0xc0000000-0xfebfffff window]
  + pci_bus 0000:00: root bus resource [mem 0xc0100000-0xfebfffff window]

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
---
 arch/x86/include/asm/e820/api.h |  5 +++++
 arch/x86/kernel/resource.c      | 17 ++++++++++++-----
 arch/x86/pci/acpi.c             |  5 +++++
 3 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/e820/api.h b/arch/x86/include/asm/e820/api.h
index e8f58ddd06d9..5a39ed59b6db 100644
--- a/arch/x86/include/asm/e820/api.h
+++ b/arch/x86/include/asm/e820/api.h
@@ -4,6 +4,9 @@
 
 #include <asm/e820/types.h>
 
+struct device;
+struct resource;
+
 extern struct e820_table *e820_table;
 extern struct e820_table *e820_table_kexec;
 extern struct e820_table *e820_table_firmware;
@@ -43,6 +46,8 @@ extern void e820__register_nosave_regions(unsigned long limit_pfn);
 
 extern int  e820__get_entry_type(u64 start, u64 end);
 
+extern void remove_e820_regions(struct device *dev, struct resource *avail);
+
 /*
  * Returns true iff the specified range [start,end) is completely contained inside
  * the ISA region.
diff --git a/arch/x86/kernel/resource.c b/arch/x86/kernel/resource.c
index 8ffe68437744..7378ea146976 100644
--- a/arch/x86/kernel/resource.c
+++ b/arch/x86/kernel/resource.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+#include <linux/dev_printk.h>
 #include <linux/ioport.h>
 #include <asm/e820/api.h>
 
@@ -23,18 +24,27 @@ static void resource_clip(struct resource *res, resource_size_t start,
 		res->start = end + 1;
 }
 
-static void remove_e820_regions(struct resource *avail)
+void remove_e820_regions(struct device *dev, struct resource *avail)
 {
+	struct resource orig = *avail;
 	int i;
 	struct e820_entry *entry;
 	u64 e820_start, e820_end;
 
+	if (!(avail->flags & IORESOURCE_MEM))
+		return;
+
 	for (i = 0; i < e820_table->nr_entries; i++) {
 		entry = &e820_table->entries[i];
 		e820_start = entry->addr;
 		e820_end = entry->addr + entry->size - 1;
 
 		resource_clip(avail, e820_start, e820_end);
+		if (orig.start != avail->start || orig.end != avail->end) {
+			dev_info(dev, "clipped %pR to %pR for e820 entry [mem %#010Lx-%#010Lx]\n",
+				 &orig, avail, e820_start, e820_end);
+			orig = *avail;
+		}
 	}
 }
 
@@ -45,9 +55,6 @@ void arch_remove_reservations(struct resource *avail)
 	 * the low 1MB unconditionally, as this area is needed for some ISA
 	 * cards requiring a memory range, e.g. the i82365 PCMCIA controller.
 	 */
-	if (avail->flags & IORESOURCE_MEM) {
+	if (avail->flags & IORESOURCE_MEM)
 		resource_clip(avail, BIOS_ROM_BASE, BIOS_ROM_END);
-
-		remove_e820_regions(avail);
-	}
 }
diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 052f1d78a562..562c81a51ea0 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c
@@ -8,6 +8,7 @@
 #include <linux/pci-acpi.h>
 #include <asm/numa.h>
 #include <asm/pci_x86.h>
+#include <asm/e820/api.h>
 
 struct pci_root_info {
 	struct acpi_pci_root_info common;
@@ -299,6 +300,10 @@ 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)
+		remove_e820_regions(&device->dev, entry->res);
+
 	if (pci_use_crs) {
 		resource_list_for_each_entry_safe(entry, tmp, &ci->resources)
 			if (resource_is_pcicfg_ioport(entry->res))
-- 
2.25.1