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[libvirt] [Patch 9/7] qemu: use standard pci-bridge in place of i82801b11-bridge



Current seabios doesn't recognize any disk device that is attached
anywhere behind an i82801b11-bridge, so it can't boot from them. (It's
possible/probable that seabios simply doesn't recognize that bridge at
all, so *no* devices behind it are available to the bios). In order to
allow booting from any disk no matter where it is attached, this patch
flouts the hardware specs (which say that only PCIe devices can be
connected directly to a PCIe bus such as the q35 machine's "pcie.0"),
taking advantage of the fact that qemu also ignores this rule, and
installs a stnadard pci-bridge device anywhere the config requests a
"dmi-to-pci-bridge (which had been setup to use i82801b11-bridge).

Because this isn't really the way things should be, the original code
is left in place, and the new code is put inside an #ifdef indicating
why it is there.
---
This is one of the solutions to the problem that I proposed here:

https://www.redhat.com/archives/libvir-list/2013-August/msg00165.html

Since this is the one I currently prefer, I implemented it (and it works!)

 src/qemu/qemu_command.c                            | 16 ++++++++++++++++
 tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args |  2 +-
 tests/qemuxml2argvdata/qemuxml2argv-q35.args       |  2 +-
 3 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c
index 3353c61..460144f 100644
--- a/src/qemu/qemu_command.c
+++ b/src/qemu/qemu_command.c
@@ -4571,7 +4571,23 @@ qemuBuildControllerDevStr(virDomainDefPtr domainDef,
                                _("dmi-to-pci-bridge index should be > 0"));
                 goto error;
             }
+#define SEABIOS_NO_I82801B11_SUPPORT
+#if defined SEABIOS_NO_I82801B11_SUPPORT
+            /* since seabios currently doesn't recognize boot devices
+             * that are anywhere behind an i82801b11-bridge, we take
+             * advantage of the fact that qemu erroneously
+             * (generously) allows us to plug a pci-bridge into a PCIe
+             * slot, and create a pci-bridge to take the place of the
+             * i82801b11-bridge. When seabios is fixed, we will figure
+             * out the best way to determine whether or not the fix is
+             * present, and switch to the more proper device when
+             * appropriate.
+             */
+            virBufferAsprintf(&buf, "pci-bridge,chassis_nr=%d,id=pci.%d",
+                              def->idx, def->idx);
+#else
             virBufferAsprintf(&buf, "i82801b11-bridge,id=pci.%d", def->idx);
+#endif
             break;
         case VIR_DOMAIN_CONTROLLER_MODEL_PCI_ROOT:
         case VIR_DOMAIN_CONTROLLER_MODEL_PCIE_ROOT:
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args b/tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args
index 84428f9..da970db 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-pcie-root.args
@@ -1,5 +1,5 @@
 LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test /usr/libexec/qemu-kvm \
 -S -M q35 -m 2048 -smp 2 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
--device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x2 \
+-device pci-bridge,chassis_nr=1,id=pci.1,bus=pcie.0,addr=0x2 \
 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1
diff --git a/tests/qemuxml2argvdata/qemuxml2argv-q35.args b/tests/qemuxml2argvdata/qemuxml2argv-q35.args
index 5ff4bc7..a0ec66e 100644
--- a/tests/qemuxml2argvdata/qemuxml2argv-q35.args
+++ b/tests/qemuxml2argvdata/qemuxml2argv-q35.args
@@ -1,6 +1,6 @@
 LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test \
 /usr/libexec/qemu-kvm -S -M q35 -m 2048 -smp 2 -nographic -nodefaults \
 -monitor unix:/tmp/test-monitor,server,nowait -no-acpi -boot c \
--device i82801b11-bridge,id=pci.1,bus=pcie.0,addr=0x2 \
+-device pci-bridge,chassis_nr=1,id=pci.1,bus=pcie.0,addr=0x2 \
 -device pci-bridge,chassis_nr=2,id=pci.2,bus=pci.1,addr=0x1 \
 -vga qxl -global qxl.ram_size=67108864 -global qxl.vram_size=18874368
-- 
1.7.11.7


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