The branch stable/14 has been updated by zlei:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=1969d82fcf62f80c2047a53b42f501680b140b0d

commit 1969d82fcf62f80c2047a53b42f501680b140b0d
Author:     Zhenlei Huang <z...@freebsd.org>
AuthorDate: 2023-11-02 09:07:11 +0000
Commit:     Zhenlei Huang <z...@freebsd.org>
CommitDate: 2023-11-02 09:10:03 +0000

    Hyper-V: vmbus: Add NULL check for vmbus_res
    
    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:          e7a9817b8d32 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
    
    (cherry picked from commit 63bf943d4af17799cef21e2bb78dd28003ce1ce5)
---
 sys/dev/hyperv/vmbus/vmbus.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/sys/dev/hyperv/vmbus/vmbus.c b/sys/dev/hyperv/vmbus/vmbus.c
index ee412e643b4f..0ea401507b79 100644
--- a/sys/dev/hyperv/vmbus/vmbus.c
+++ b/sys/dev/hyperv/vmbus/vmbus.c
@@ -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");

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