linux-kernel - Re: [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

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Message-ID: <56056E1D.80307@oracle.com>
Date:	Fri, 25 Sep 2015 11:54:05 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Vitaly Kuznetsov <vkuznets@...hat.com>
CC:	xen-devel@...ts.xenproject.org, x86@...nel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

On 09/25/2015 09:59 AM, Konrad Rzeszutek Wilk wrote:
> On Fri, Sep 25, 2015 at 11:59:52AM +0200, Vitaly Kuznetsov wrote:
>> Currently there is a number of issues preventing PVHVM Xen guests from
>> doing successful kexec/kdump:
>> - Bound event channels.
>> - Registered vcpu_info.
>> - PIRQ/emuirq mappings.
>> - shared_info frame after XENMAPSPACE_shared_info operation.
>> - Active grant mappings.
>> Basically, newly booted kernel stumbles upon already set up Xen interfaces
>> and there is no way to reestablish them. In Xen-4.7 a new feature called
>> 'soft reset' is coming. A guest performing kexec/kdump operation is
>> supposed to call SCHEDOP_shutdown hypercall with SHUTDOWN_soft_reset reason
>> before jumping to new kernel. Hypervisor (with some help from toolstack)
>> will do full domain cleanup (but keeping its memory and vCPU contexts
>> intact) returning the guest to the state it had when it was first booted
>> and thus allowing it to start over.
>>
>> Doing SHUTDOWN_soft_reset on Xen hypervisors which don't support it is
>> probably OK as by default all unknown shutdown reasons cause domain destroy
>> with a message in toolstack log:
>> 'Unknown shutdown reason code 5. Destroying domain.'
>> which gives a clue to what the problem is and eliminates false
>> expectations.
>>
>> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
>
> with s/pvhvm/hvm/
>
> to match with the rest of the file.
>
> Thanks.
>>   
>> +#ifdef CONFIG_KEXEC_CORE
>> +static void xen_pvhvm_kexec_shutdown(void)
>> +{
>> +	native_machine_shutdown();
>> +	if (kexec_in_progress)
>> +		xen_reboot(SHUTDOWN_soft_reset);
>> +}

This routine is not kexec-specific so "kexec_" should be dropped from 
the name.

Also, I am not sure I see how this new op will be used in the hypervisor 
--- currently AFAICS it is only processed under is_hardware_domain(). 
Are there other patches that will support HVM guests?


-boris

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