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

On 11/2/23, Zhenlei Huang <zlei@freebsd.org> wrote:
> Sorry I committed too fast.
>
> I should give credentials to Souradeep in the commit message.
>
> Thank him for the analysis !
>

again this kind of change you can revert and recommit with proper
authorship, as long as it happens fast

>> On Nov 2, 2023, at 5:09 PM, Zhenlei Huang <zlei@FreeBSD.org> wrote:
>>
>> 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");
>
>
>
>


-- 
Mateusz Guzik <mjguzik gmail.com>