git: 63bf943d4af1 - main - Hyper-V: vmbus: Add NULL check for vmbus_res

The branch main has been updated by zlei:

URL: https://cgit.FreeBSD.org/src/commit/?id=63bf943d4af17799cef21e2bb78dd28003ce1ce5

commit 63bf943d4af17799cef21e2bb78dd28003ce1ce5
Author:     Zhenlei Huang <zlei@FreeBSD.org>
AuthorDate: 2023-11-02 09:07:11 +0000
Commit:     Zhenlei Huang <zlei@FreeBSD.org>
CommitDate: 2023-11-02 09:07:11 +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
---
 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");