Re: [Qemu-devel] [PATCH v5 for-2.3 27/28] apci: fix PXB behaviour if used with unsupported BIOS

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Mar 10, 2015 at 06:19:43PM +0200, Marcel Apfelbaum wrote:
> On 03/10/2015 05:44 PM, Michael S. Tsirkin wrote:
> >On Tue, Mar 10, 2015 at 05:32:13PM +0200, Marcel Apfelbaum wrote:
> >>PXB does not work with an unsupported BIOS, but should
> >>not interfere with normal OS operation.
> >>
> >>Fix this by not adding PXB mem/IO chunks to _CRS
> >>if they weren't configured by BIOS.
> >>
> >>Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> >>---
> >>  hw/i386/acpi-build.c | 71 +++++++++++++++++++++++++++++++---------------------
> >>  1 file changed, 42 insertions(+), 29 deletions(-)
> >>
> >>diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
> >>index 2bc8a80..416972c 100644
> >>--- a/hw/i386/acpi-build.c
> >>+++ b/hw/i386/acpi-build.c
> >>@@ -780,6 +780,10 @@ static Aml *build_crs(PcPciInfo *pci, PciInfo *bus_info,
> >>              range_base = region->value->address;
> >>              range_limit = region->value->address + region->value->size - 1;
> >>
> >>+            if (range_base == PCI_BAR_UNMAPPED) {
> >>+                continue;
> >>+            }
> >>+
> >>              if (!strcmp(region->value->type, "io")) {
> >>                  aml_append(crs,
> >>                      aml_word_io(aml_min_fixed, aml_max_fixed,
> >>@@ -813,41 +817,50 @@ static Aml *build_crs(PcPciInfo *pci, PciInfo *bus_info,
> >>
> >>              range_base = bridge_info->bus.io_range->base;
> >>              range_limit = bridge_info->bus.io_range->limit;
> >>-            aml_append(crs,
> >>-                aml_word_io(aml_min_fixed, aml_max_fixed,
> >>-                            aml_pos_decode, aml_entire_range,
> >>-                            0,
> >>-                            range_base,
> >>-                            range_limit,
> >>-                            0,
> >>-                            range_limit - range_base + 1));
> >>-            crs_range_insert(io_ranges, range_base, range_limit);
> >>+            /* PCI Bridge I/O limit is aligned to 4K */
> >
> >Can't say this comment explains anything.
> >So it's aligned - thus if (range_limit >> 12) is same as
> >if (range_limit).
> I'll use range_base == 0 as invalid value.
> 
> Thanks,
> Marcel

It's also just a work-around for old broken bioses.
We don't ship them anymore, but it's reasonable
to keep around until we update the bios in qemu.
However, pls add a comment to this end.

> >
> >Also, generally you should test limit>base for bridges.
> 
> >
> >>+            if (range_limit >> 12) {
> >>+                aml_append(crs,
> >>+                    aml_word_io(aml_min_fixed, aml_max_fixed,
> >>+                                aml_pos_decode, aml_entire_range,
> >>+                                0,
> >>+                                range_base,
> >>+                                range_limit,
> >>+                                0,
> >>+                                range_limit - range_base + 1));
> >>+                crs_range_insert(io_ranges, range_base, range_limit);
> >>+            }
> >>
> >>              range_base = bridge_info->bus.memory_range->base;
> >>              range_limit = bridge_info->bus.memory_range->limit;
> >>-             aml_append(crs,
> >>-                aml_dword_memory(aml_pos_decode, aml_min_fixed,
> >>-                                 aml_max_fixed, aml_non_cacheable,
> >>-                                 aml_ReadWrite,
> >>-                                 0,
> >>-                                 range_base,
> >>-                                 range_limit,
> >>-                                 0,
> >>-                                 range_limit - range_base + 1));
> >>-            crs_range_insert(mem_ranges, range_base, range_limit);
> >>+            /* PCI Bridge MEM limit is aligned to 1M */
> >
> >same comment here.
> >
> >>+            if (range_limit >> 20) {
> >>+                aml_append(crs,
> >>+                    aml_dword_memory(aml_pos_decode, aml_min_fixed,
> >>+                                     aml_max_fixed, aml_non_cacheable,
> >>+                                     aml_ReadWrite,
> >>+                                     0,
> >>+                                     range_base,
> >>+                                     range_limit,
> >>+                                     0,
> >>+                                     range_limit - range_base + 1));
> >>+                    crs_range_insert(mem_ranges, range_base, range_limit);
> >>+            }
> >>
> >>              range_base = bridge_info->bus.prefetchable_range->base;
> >>              range_limit = bridge_info->bus.prefetchable_range->limit;
> >>-            aml_append(crs,
> >>-                aml_dword_memory(aml_pos_decode, aml_min_fixed,
> >>-                                 aml_max_fixed, aml_non_cacheable,
> >>-                                 aml_ReadWrite,
> >>-                                 0,
> >>-                                 range_base,
> >>-                                 range_limit,
> >>-                                 0,
> >>-                                 range_limit - range_base + 1));
> >>-            crs_range_insert(mem_ranges, range_base, range_limit);
> >>+            /* PCI Bridge Prefetch MEM limit is aligned to 1M */
> >>+            if (range_limit >> 20) {
> >>+                aml_append(crs,
> >>+                    aml_dword_memory(aml_pos_decode, aml_min_fixed,
> >>+                                     aml_max_fixed, aml_non_cacheable,
> >>+                                     aml_ReadWrite,
> >>+                                     0,
> >>+                                     range_base,
> >>+                                     range_limit,
> >>+                                     0,
> >>+                                     range_limit - range_base + 1));
> >>+                crs_range_insert(mem_ranges, range_base, range_limit);
> >>+            }
> >>          }
> >>      }
> >>
> >>--
> >>2.1.0