[libvirt] [PATCH] libxl: add support for soft reset

[Jim Fehlig]

On 10/30/18 3:18 AM, Michal Privoznik wrote:
> On 10/30/2018 03:17 AM, Jim Fehlig wrote:
>> On 10/29/18 7:26 PM, Jim Fehlig wrote:
>>> The pvops Linux kernel implements machine_ops.crash_shutdown as
>>>
>>> static void xen_hvm_crash_shutdown(struct pt_regs *regs)
>>> {
>>>           native_machine_crash_shutdown(regs);
>>>           xen_reboot(SHUTDOWN_soft_reset);
>>> }
>>>
>>> but currently the libxl driver does not handle the soft reset
>>> shutdown event. As a result, the guest domain never proceeds
>>> past xen_reboot(), making it impossible for HVM domains to save
>>> a crash dump using kexec.
>>>
>>> This patch adds support for handling the soft reset event by
>>> calling libxl_domain_soft_reset() and re-enabling domain death
>>> events, which is similar to the xl tool handling of soft reset
>>> shutdown event.
>>>
>>> Signed-off-by: Jim Fehlig <jfehlig at suse.com>
>>> ---
>>>    src/libxl/libxl_domain.c | 30 ++++++++++++++++++++++++++++++
>>>    1 file changed, 30 insertions(+)
>>>
>>> diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
>>> index 0032b9dd11..295ec04a85 100644
>>> --- a/src/libxl/libxl_domain.c
>>> +++ b/src/libxl/libxl_domain.c
>>> @@ -447,8 +447,10 @@ libxlDomainShutdownThread(void *opaque)
>>>        virObjectEventPtr dom_event = NULL;
>>>        libxl_shutdown_reason xl_reason =
>>> ev->u.domain_shutdown.shutdown_reason;
>>>        libxlDriverConfigPtr cfg;
>>> +    libxl_domain_config d_config;
>>>          cfg = libxlDriverConfigGet(driver);
>>> +    libxl_domain_config_init(&d_config);
>>>          vm = virDomainObjListFindByID(driver->domains, ev->domid);
>>>        if (!vm) {
>>> @@ -532,6 +534,33 @@ libxlDomainShutdownThread(void *opaque)
>>>             * after calling libxl_domain_suspend() are handled by it's
>>> callers.
>>>             */
>>>            goto endjob;
>>> +    } else if (xl_reason == LIBXL_SHUTDOWN_REASON_SOFT_RESET) {
>>> +        libxlDomainObjPrivatePtr priv = vm->privateData;
>>> +        int res;
>>
>> I'm not sure why I have this useless local. I've squashed the below diff
>> into my local branch.
> 
> ACK

Thanks, but I found this didn't compile with Xen 4.6, our minimum supported Xen 
version. Soft reset was introduced in 4.7. I've sent a V2, which includes some 
cleanups to the libxlDomainShutdownThread function. Thanks for looking at it if 
you have time

https://www.redhat.com/archives/libvir-list/2018-October/msg01370.html

Regards,
Jim