linux-kernel - RE: [PATCH v3] PCI: hv: Fix a timing issue which causes kdump to fail occasionally

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Message-ID: <MW2PR2101MB105217EA920CDA1600449D3AD77B0@MW2PR2101MB1052.namprd21.prod.outlook.com>
Date:   Mon, 20 Jul 2020 16:27:59 +0000
From:   Michael Kelley <mikelley@...rosoft.com>
To:     Wei Hu <weh@...rosoft.com>, 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>
Subject: RE: [PATCH v3] PCI: hv: Fix a timing issue which causes kdump to fail
 occasionally

From: Wei Hu <weh@...rosoft.com> Sent: Friday, July 17, 2020 8:48 PM
> To: 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>
> Cc: Wei Hu <weh@...rosoft.com>
> Subject: [PATCH v3] PCI: hv: Fix a timing issue which causes kdump to fail occasionally
> 
> Kdump could fail sometime on Hyper-V guest over Accelerated Network
> interface. This is because the retry in hv_pci_enter_d0() relies on
> an asynchronous host event arriving before the guest calls
> hv_send_resources_allocated(). Fix the problem by moving retry
> to hv_pci_probe(), removing this dependency and making the calling
> sequence synchronous.
> 
> Fixes: c81992e7f4aa ("PCI: hv: Retry PCI bus D0 entry on invalid device state")
> Signed-off-by: Wei Hu <weh@...rosoft.com>
> ---
>     v2: Adding Fixes tag according to Michael Kelley's review comment.
>     v3: Fix couple typos and reword commit message to make it clearer.
>     Thanks the comments from Bjorn Helgaas.
> 
>  drivers/pci/controller/pci-hyperv.c | 66 ++++++++++++++---------------
>  1 file changed, 32 insertions(+), 34 deletions(-)
> 

I gave my Reviewed-by on the earlier v1 of this patch, but reiterating it
here:

Reviewed-by: Michael Kelley <mikelley@...rosoft.com>