Re: [Qemu-devel] [PATCH v3 0/9] HyperV equivalent of pvpanic driver

["Denis V. Lunev" <den@openvz.org>]

On 30/06/15 15:26, Daniel P. Berrange wrote:
> On Tue, Jun 30, 2015 at 02:33:18PM +0300, Denis V. Lunev wrote:
>> Windows 2012 guests can notify hypervisor about occurred guest crash
>> (Windows bugcheck(BSOD)) by writing specific Hyper-V msrs. This patch does
>> handling of this MSR's by KVM and sending notification to user space that
>> allows to gather Windows guest crash dump by QEMU/LIBVIRT.
>>
>> The idea is to provide functionality equal to pvpanic device without
>> QEMU guest agent for Windows.
> That's nice - do you know if the Linux kernel (or any other non-Win2k12
> kernels) have support for notifying hypevisors via this Hyper-V msr,
> when running as a guest ?
>
> Regards,
> Daniel
Linux for sure is able to do that if configured to run
on top of Hyper-V

drivers/hv/vmbus_drv.c:
static int hyperv_panic_event(struct notifier_block *nb,
                         unsigned long event, void *ptr)
{
         struct pt_regs *regs;

         regs = current_pt_regs();

         wrmsrl(HV_X64_MSR_CRASH_P0, regs->ip);
         wrmsrl(HV_X64_MSR_CRASH_P1, regs->ax);
         wrmsrl(HV_X64_MSR_CRASH_P2, regs->bx);
         wrmsrl(HV_X64_MSR_CRASH_P3, regs->cx);
         wrmsrl(HV_X64_MSR_CRASH_P4, regs->dx);

         /*
          * Let Hyper-V know there is crash data available
          */
         wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
         return NOTIFY_DONE;
}

Regards,
     Den