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Subject: Re: [PATCH] asm-generic/hyperv: Fix struct hv_message_header ordering
Date:   Fri, 30 Jul 2021 11:35:57 +0200
From:   Siddharth Chandrasekaran <sidcha@amazon.de>
To:     Wei Liu <wei.liu@kernel.org>
CC:     Vitaly Kuznetsov <vkuznets@redhat.com>,
        Siddharth Chandrasekaran <sidcha.dev@gmail.com>,
        Liran Alon <liran@amazon.com>,
        Ioannis Aslanidis <iaslan@amazon.de>,
        <linux-hyperv@vger.kernel.org>, <linux-arch@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>,
        "K. Y. Srinivasan" <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Dexuan Cui <decui@microsoft.com>, Arnd Bergmann <arnd@arndb.de>
Message-ID: <20210730091649.GA13442@u366d62d47e3651.ant.amazon.com>
References: <20210729133702.11383-1-sidcha@amazon.de>
 <87eebh9qhd.fsf@vitty.brq.redhat.com>
 <20210729140705.wj5tokeq6lkxm2yy@liuwe-devbox-debian-v2>
 <20210729142652.GA25242@uc8bbc9586ea454.ant.amazon.com>
 <20210729165638.f5idr2ag3pdbpd6u@liuwe-devbox-debian-v2>
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On Thu, Jul 29, 2021 at 04:56:38PM +0000, Wei Liu wrote:
> On Thu, Jul 29, 2021 at 04:26:54PM +0200, Siddharth Chandrasekaran wrote:
> > On Thu, Jul 29, 2021 at 02:07:05PM +0000, Wei Liu wrote:
> > > On Thu, Jul 29, 2021 at 03:52:46PM +0200, Vitaly Kuznetsov wrote:
> > > > Siddharth Chandrasekaran <sidcha@amazon.de> writes:
> > > >
> > > > > According to Hyper-V TLFS Version 6.0b, struct hv_message_header members
> > > > > should be defined in the order:
> > > > >
> > > > >     message_type, reserved, message_flags, payload_size
> > > > >
> > > > > but we have it defined in the order:
> > > > >
> > > > >     message_type, payload_size, message_flags, reserved
> > > > >
> > > > > that is, the payload_size and reserved members swapped.
> > > >
> > > > Indeed,
> > > >
> > > > typedef struct
> > > > {
> > > >       HV_MESSAGE_TYPE MessageType;
> > > >       UINT16 Reserved;
> > > >       HV_MESSAGE_FLAGS MessageFlags;
> > > >       UINT8 PayloadSize;
> > > >       union
> > > >       {
> > > >               UINT64 OriginationId;
> > > >               HV_PARTITION_ID Sender;
> > > >               HV_PORT_ID Port;
> > > >       };
> > > > } HV_MESSAGE_HEADER;
> > >
> > > Well. I think TLFS is wrong. Let me ask around.
> >
> > TBH, I hadn't considered that possibility :). I assumed it was a
> > regression on our side. But I spent some time tracing the history of that
> > struct all the way back to when it was in staging (in 2009) and now I'm
> > inclined to believe a later version of TLFS is at fault here.
> >
> > Based on what we decide in this thread, I will open an issue on the TLFS
> > GitHub repository.
> >
> 
> I have confirmation TLFS is wrong and shall be fixed. Feel free to open
> an issue on GitHub too.

Thanks for the confirmation, I created an issue [1] to track this.

~ Sid.

[1]: https://github.com/MicrosoftDocs/Virtualization-Documentation/issues/1624


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