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RE: [PATCH 2/2] PCI: hv: handle all pending messages in hv_pci_onchannelcallback()

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> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, May 30, 2016 7:18 AM
> To: linux-pci@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org; devel@linuxdriverproject.org; Bjorn
> Helgaas <bhelgaas@google.com>; Haiyang Zhang
> <haiyangz@microsoft.com>; KY Srinivasan <kys@microsoft.com>; Jake
> Oshins <jakeo@microsoft.com>
> Subject: [PATCH 2/2] PCI: hv: handle all pending messages in
> hv_pci_onchannelcallback()
> 
> When we have an interrupt from host we have a bit set in event page
> indicating there are messages for the particular channel. We need to read
> them all as we won't get signaled for what was on the queue before we
> cleared the bit in vmbus_on_event(). This applies to all Hyper-V drivers
> and the pass-through driver should do the same.
> I did non meet any bugs, the issue was found by code inspection. We don't
> have many events going through hv_pci_onchannelcallback(), this explains
> why nobody reported the issue before.
> 
> While on it, fix handling non-zero vmbus_recvpacket_raw() return values by
> dropping out. If the return value is not zero it is wrong to inspect
> buffer or bytes_recvd as these may contain invalid data.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Acked-by: Jake Oshins <jakeo@microsoft.com>

> ---
>  drivers/pci/host/pci-hyperv.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
> index a68ec49..7de341d 100644
> --- a/drivers/pci/host/pci-hyperv.c
> +++ b/drivers/pci/host/pci-hyperv.c
> @@ -1657,12 +1657,16 @@ static void hv_pci_onchannelcallback(void
> *context)
>  			continue;
>  		}
> 
> +		/* Zero length indicates there are no more packets. */
> +		if (ret || !bytes_recvd)
> +			break;
> +
>  		/*
>  		 * All incoming packets must be at least as large as a
>  		 * response.
>  		 */
>  		if (bytes_recvd <= sizeof(struct pci_response))
> -			break;
> +			continue;
>  		desc = (struct vmpacket_descriptor *)buffer;
> 
>  		switch (desc->type) {
> @@ -1724,7 +1728,6 @@ static void hv_pci_onchannelcallback(void
> *context)
>  				desc->type, req_id, bytes_recvd);
>  			break;
>  		}
> -		break;
>  	}
> 
>  	kfree(buffer);
> --
> 2.5.5

This is good, too.

Thanks,
Jake Oshins

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[PATCH 0/2] PCI: hv: fix a couple of issues in hv_pci_onchannelcallback() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-05-30 16:20 +0200
  [PATCH 2/2] PCI: hv: handle all pending messages in hv_pci_onchannelcallback() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-05-30 16:20 +0200
    RE: [PATCH 2/2] PCI: hv: handle all pending messages in  hv_pci_onchannelcallback() Jake Oshins <jakeo@microsoft.com> - 2016-05-31 19:40 +0200
  [PATCH 1/2] PCI: hv: don't leak buffer in hv_pci_onchannelcallback() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-05-30 16:20 +0200
    RE: [PATCH 1/2] PCI: hv: don't leak buffer in  hv_pci_onchannelcallback() Jake Oshins <jakeo@microsoft.com> - 2016-05-31 20:10 +0200
  Re: [PATCH 0/2] PCI: hv: fix a couple of issues in hv_pci_onchannelcallback() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-06-10 14:10 +0200
    Re: [PATCH 0/2] PCI: hv: fix a couple of issues in  hv_pci_onchannelcallback() Bjorn Helgaas <helgaas@kernel.org> - 2016-06-10 17:40 +0200
  Re: [PATCH 0/2] PCI: hv: fix a couple of issues in  hv_pci_onchannelcallback() Bjorn Helgaas <helgaas@kernel.org> - 2016-06-11 02:00 +0200

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