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Re: [Qemu-devel] [PATCH qemu] pci: Only unmap bus_master_enabled_region

From: Marcel Apfelbaum
Subject: Re: [Qemu-devel] [PATCH qemu] pci: Only unmap bus_master_enabled_region if was added previously
Date: Fri, 31 Mar 2017 15:08:49 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1

On 03/31/2017 07:47 AM, Alexey Kardashevskiy wrote:
Normally pci_init_bus_master() would be called either via
bus->machine_done.notify or directly from do_pci_register_device().

However if a device's realize() failed, pci_init_bus_master() is not
called, and do_pci_unregister_device() fails on
memory_region_del_subregion() as it was not mapped.

This adds a check that subregion was mapped before unmapping it.

Fixes: c53598ed18e4 ("pci: Add missing drop of bus master AS reference")
Signed-off-by: Alexey Kardashevskiy <address@hidden>
This is to pass iotest 051 which does run QEMU like this:

ppc64-softmmu/qemu-system-ppc64 -nodefaults -machine accel=qtest -nographic 
-monitor stdio -serial none -drive if=virtio

which normally fails with:

qemu-system-ppc64: -drive if=virtio: Device needs media, but drive is empty

or asserts (without this patch):

qemu-system-ppc64: /home/aik/p/qemu-kvm/memory.c:2118: 
memory_region_del_subregion: Assertion `subregion->container == mr' failed.
 hw/pci/pci.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index bd8043c460..259483b1c0 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -869,8 +869,10 @@ static void do_pci_unregister_device(PCIDevice *pci_dev)
     pci_dev->bus->devices[pci_dev->devfn] = NULL;

-    memory_region_del_subregion(&pci_dev->bus_master_container_region,
-                                &pci_dev->bus_master_enable_region);
+    if (memory_region_is_mapped(&pci_dev->bus_master_enable_region)) {
+        memory_region_del_subregion(&pci_dev->bus_master_container_region,
+                                    &pci_dev->bus_master_enable_region);
+    }


Reviewed-by: Marcel Apfelbaum <address@hidden>


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