[Qemu-devel] [PULL 42/42] i386/acpi-build: fix PXB workarounds for unsupported BIOSes

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

From: Laszlo Ersek <lersek@redhat.com>

The patch

  apci: fix PXB behaviour if used with unsupported BIOS

uses the following condition to see if a "PXB mem/IO chunk" has *not* been
configured by the BIOS:

  (!range_base || range_base > range_limit)

When this condition evaluates to true, said patch *omits* the
corresponding entry from the _CRS.

Later on the patch checks for the opposite condition (with the intent of
*adding* entries to the _CRS if the "PXB mem/IO chunks" *have* been
configured). Unfortunately, the condition was negated incorrectly: only
the first ! operator was removed, which led to the nonsensical expression

  (range_base || range_base > range_limit)

leading to bogus entries in the _CRS, and causing BSOD in Windows Server
2012 R2 when it runs on OVMF.

The correct negative of the condition seen at the top is

  (range_base && range_base <= range_limit)

Fix the expressions.

Cc: Marcel Apfelbaum <marcel@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/i386/acpi-build.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 8fae3b9..8e88ade 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -832,7 +832,7 @@ static Aml *build_crs(PCIHostState *host,
              * Work-around for old bioses
              * that do not support multiple root buses
              */
-            if (range_base || range_base > range_limit) {
+            if (range_base && range_base <= range_limit) {
                 aml_append(crs,
                            aml_word_io(AML_MIN_FIXED, AML_MAX_FIXED,
                                        AML_POS_DECODE, AML_ENTIRE_RANGE,
@@ -853,7 +853,7 @@ static Aml *build_crs(PCIHostState *host,
              * Work-around for old bioses
              * that do not support multiple root buses
              */
-            if (range_base || range_base > range_limit) {
+            if (range_base && range_base <= range_limit) {
                 aml_append(crs,
                            aml_dword_memory(AML_POS_DECODE, AML_MIN_FIXED,
                                             AML_MAX_FIXED, AML_NON_CACHEABLE,
@@ -864,7 +864,7 @@ static Aml *build_crs(PCIHostState *host,
                                             0,
                                             range_limit - range_base + 1));
                 crs_range_insert(mem_ranges, range_base, range_limit);
-          }
+            }
 
             range_base =
                 pci_bridge_get_base(dev, PCI_BASE_ADDRESS_MEM_PREFETCH);
@@ -875,7 +875,7 @@ static Aml *build_crs(PCIHostState *host,
              * Work-around for old bioses
              * that do not support multiple root buses
              */
-            if (range_base || range_base > range_limit) {
+            if (range_base && range_base <= range_limit) {
                 aml_append(crs,
                            aml_dword_memory(AML_POS_DECODE, AML_MIN_FIXED,
                                             AML_MAX_FIXED, AML_NON_CACHEABLE,
-- 
MST