linux-kernel - RE: [PATCH v2] PCI: hv: Fix a timing issue which causes kdump to fail occasionally

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Message-ID: <SG2P153MB0377A7193C7038BD1512EACCBB7D0@SG2P153MB0377.APCP153.PROD.OUTLOOK.COM>
Date:   Sat, 18 Jul 2020 03:46:19 +0000
From:   Wei Hu <weh@...rosoft.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "robh@...nel.org" <robh@...nel.org>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>
Subject: RE: [PATCH v2] PCI: hv: Fix a timing issue which causes kdump to fail
 occasionally



> -----Original Message-----
> From: Bjorn Helgaas <helgaas@...nel.org>
> Sent: Saturday, July 18, 2020 4:11 AM
> To: Wei Hu <weh@...rosoft.com>
> Cc: KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang
> <haiyangz@...rosoft.com>; Stephen Hemminger <sthemmin@...rosoft.com>;
> wei.liu@...nel.org; lorenzo.pieralisi@....com; robh@...nel.org;
> bhelgaas@...gle.com; linux-hyperv@...r.kernel.org; linux-
> pci@...r.kernel.org; linux-kernel@...r.kernel.org; Dexuan Cui
> <decui@...rosoft.com>; Michael Kelley <mikelley@...rosoft.com>
> Subject: Re: [PATCH v2] PCI: hv: Fix a timing issue which causes kdump to fail
> occasionally
> 
> On Fri, Jul 17, 2020 at 10:55:28AM +0800, Wei Hu wrote:
> > Kdump could fail sometime on HyperV guest over Accerlated Network
> > interface. This is because the retry in hv_pci_enter_d0() relies on an
> > asynchronous host event to arrive guest before calling
> > hv_send_resources_allocated(). This fixes the problem by moving retry
> > to hv_pci_probe(), removing this dependence and making the calling
> > sequence synchronous.
> 
> Lorenzo, if you apply this, can you fix this typo?
> 
>   s/Accerlated/Accelerated/
> 
> and maybe even
> 
>   s/HyperV/Hyper-V/
>   s/This fixes the problem/Fix the problem/
>   s/this dependence/this dependency/
> 
> Not sure if "relies on ... event to arrive guest" means "relies on ...
> event arriving in the guest"?  Or maybe "relies on ... event arriving before the
> guest calls ..."?
> 
> This would probably all make perfect sense to me if I understood more about
> Hyper-V :)
> 
> > v2: Adding Fixes tag according to Michael Kelley's review comment.
> 
> There's no need to include this "v2" comment in the commit log.  I think if you
> put it after a line containing only "---" (or maybe "--"?), it will be in the email
> but not in the commit log.
> 
Thanks Bjorn. I will send out a v3 version shortly to correct all these. 
Lorenzo, please pick up my v3 version if you have not started to apply it yet. 

Thanks so much,
Wei