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[PULL,4/5] Revert "acpi/gpex: Inform os to keep firmware resource map"

Message ID 20210803205043.165034-5-mst@redhat.com
State New
Headers show
Series [PULL,1/5] hw/pcie-root-port: Fix hotplug for PCI devices requiring IO | expand

Commit Message

Michael S. Tsirkin Aug. 3, 2021, 8:52 p.m. UTC 
This reverts commit 0cf8882fd06ba0aeb1e90fa6f23fce85504d7e14.

Which this commit, with aarch64 when using efi PCI devices with IO ports
do not work.  The reason is that EFI creates I/O port mappings below
0x1000 (in fact, at 0). However Linux, for legacy reasons, does not
support I/O ports <= 0x1000 on PCI, so the I/O assignment created by EFI
is rejected.

EFI creates the mappings primarily for itself, and up until DSM #5
started to be enforced, all PCI resource allocations that existed at
boot were ignored by Linux and recreated from scratch.

Also, the commit in question looks dubious - it seems unlikely that
Linux would fail to create a resource tree. What does
happen is that BARs get moved around, which may cause trouble in some
cases: for instance, Linux had to add special code to the EFI framebuffer
driver to copy with framebuffer BARs being relocated.

DSM #5 has a long history of debate and misinterpretation.

Link: https://lore.kernel.org/r/20210724185234.GA2265457@roeck-us.net/
Fixes: 0cf8882fd06 ("acpi/gpex: Inform os to keep firmware resource map")
Reported-by: Guenter Roeck <linux@roeck-us.net>
Suggested-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/pci-host/gpex-acpi.c | 20 ++------------------
 1 file changed, 2 insertions(+), 18 deletions(-)
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Patch

diff --git a/hw/pci-host/gpex-acpi.c b/hw/pci-host/gpex-acpi.c
index 0f01f13a6e..e7e162a00a 100644
--- a/hw/pci-host/gpex-acpi.c
+++ b/hw/pci-host/gpex-acpi.c
@@ -112,26 +112,10 @@  static void acpi_dsdt_add_pci_osc(Aml *dev)
     UUID = aml_touuid("E5C937D0-3553-4D7A-9117-EA4D19C3434D");
     ifctx = aml_if(aml_equal(aml_arg(0), UUID));
     ifctx1 = aml_if(aml_equal(aml_arg(2), aml_int(0)));
-    uint8_t byte_list[] = {
-                0x1 << 0 /* support for functions other than function 0 */ |
-                0x1 << 5 /* support for function 5 */
-                };
-    buf = aml_buffer(ARRAY_SIZE(byte_list), byte_list);
+    uint8_t byte_list[1] = {1};
+    buf = aml_buffer(1, byte_list);
     aml_append(ifctx1, aml_return(buf));
     aml_append(ifctx, ifctx1);
-
-    /*
-     * PCI Firmware Specification 3.1
-     * 4.6.5. _DSM for Ignoring PCI Boot Configurations
-     */
-    /* Arg2: Function Index: 5 */
-    ifctx1 = aml_if(aml_equal(aml_arg(2), aml_int(5)));
-    /*
-     * 0 - The operating system must not ignore the PCI configuration that
-     *     firmware has done at boot time.
-     */
-    aml_append(ifctx1, aml_return(aml_int(0)));
-    aml_append(ifctx, ifctx1);
     aml_append(method, ifctx);
 
     byte_list[0] = 0;