linux-kernel - Re: [PATCH 0/2] hyperv compose_msi

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Message-ID: <bc89b8b4-d2df-c664-51f5-5f8e468f6215@quicinc.com>
Date:   Wed, 11 May 2022 09:21:34 -0600
From:   Jeffrey Hugo <quic_jhugo@...cinc.com>
To:     Wei Liu <wei.liu@...nel.org>
CC:     <kys@...rosoft.com>, <haiyangz@...rosoft.com>,
        <sthemmin@...rosoft.com>, <decui@...rosoft.com>,
        <lorenzo.pieralisi@....com>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <jakeo@...rosoft.com>,
        <dazhan@...rosoft.com>, <linux-hyperv@...r.kernel.org>,
        <linux-pci@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/2] hyperv compose_msi_msg fixups

On 5/11/2022 9:19 AM, Wei Liu wrote:
> On Wed, May 11, 2022 at 08:47:23AM -0600, Jeffrey Hugo wrote:
>> On 5/11/2022 8:41 AM, Wei Liu wrote:
>>> On Mon, May 09, 2022 at 03:48:20PM -0600, Jeffrey Hugo wrote:
>>>> While multi-MSI appears to work with pci-hyperv.c, there was a concern about
>>>> how linux was doing the ITRE allocations.  Patch 2 addresses the concern.
>>>>
>>>> However, patch 2 exposed an issue with how compose_msi_msg() was freeing a
>>>> previous allocation when called for the Nth time.  Imagine a driver using
>>>> pci_alloc_irq_vectors() to request 32 MSIs.  This would cause compose_msi_msg()
>>>> to be called 32 times, once for each MSI.  With patch 2, MSI0 would allocate
>>>> the ITREs needed, and MSI1-31 would use the cached information.  Then the driver
>>>> uses request_irq() on MSI1-17.  This would call compose_msi_msg() again on those
>>>> MSIs, which would again use the cached information.  Then unmask() would be
>>>> called to retarget the MSIs to the right VCPU vectors.  Finally, the driver
>>>> calls request_irq() on MSI0.  This would call conpose_msi_msg(), which would
>>>> free the block of 32 MSIs, and allocate a new block.  This would undo the
>>>> retarget of MSI1-17, and likely leave those MSIs targeting invalid VCPU vectors.
>>>> This is addressed by patch 1, which is introduced first to prevent a regression.
>>>>
>>>> Jeffrey Hugo (2):
>>>>     PCI: hv: Reuse existing ITRE allocation in compose_msi_msg()
>>>>     PCI: hv: Fix interrupt mapping for multi-MSI
>>>>
>>>
>>> Applied to hyperv-next. Thanks.
>>
>> Huh?  I thought you wanted a V2.  I was intending on sending that out today.
>>
> 
> Please send them out. I will apply the new version.

Sure, sending shortly.

-Jeff