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Hyper-V: vmbus: Add NULL check for vmbus_res

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QEMU emulates Hyper-V [1] but lacks the emulation for vmbus_res, thus no
coherence information is available. Add NULL check for it and fallback
to no coherence. This will prevent FreeBSD guests from panic on QEMU
with the Hyper-V enlightenment hv-synic enabled.

For real Hyper-V, both gen1 and gen2 have vmbus_res then they are not
affected by this change.

1. https://www.qemu.org/docs/master/system/i386/hyperv.html

PR:		274810
Reviewed by:	mhorne, emaste, delphij, whu
Diagnosed by:	mhorne
Fixes:		e7a9817b8d Hyper-V: vmbus: implementat bus_get_dma_tag in vmbus
Insta-MFC approved by:	re (delphij) for 14.0-RC4
Differential Revision:	https://reviews.freebsd.org/D42414
This commit is contained in:
Zhenlei Huang 2023-11-02 17:07:11 +08:00
parent 1d46c8e5c2
commit 63bf943d4a
1 changed files with 6 additions and 4 deletions
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10
sys/dev/hyperv/vmbus/vmbus.c
View file

@ -1393,7 +1393,7 @@ vmbus_doattach(struct vmbus_softc *sc)
int ret;
device_t dev_res;
ACPI_HANDLE handle;
unsigned int coherent;
unsigned int coherent = 0;
if (sc->vmbus_flags & VMBUS_FLAG_ATTACHED)
return (0);
@ -1416,10 +1416,12 @@ vmbus_doattach(struct vmbus_softc *sc)
/* Coherency attribute */
dev_res = devclass_get_device(devclass_find("vmbus_res"), 0);
handle = acpi_get_handle(dev_res);
if (dev_res != NULL) {
handle = acpi_get_handle(dev_res);
if (ACPI_FAILURE(acpi_GetInteger(handle, "_CCA", &coherent)))
coherent = 0;
if (ACPI_FAILURE(acpi_GetInteger(handle, "_CCA", &coherent)))
coherent = 0;
}
if (bootverbose)
device_printf(sc->vmbus_dev, "Bus is%s cache-coherent\n",
coherent ? "" : " not");