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Date:   Thu, 29 Jul 2021 16:56:38 +0000
From:   Wei Liu <wei.liu@kernel.org>
To:     Siddharth Chandrasekaran <sidcha@amazon.de>
Cc:     Wei Liu <wei.liu@kernel.org>,
        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>
Subject: Re: [PATCH] asm-generic/hyperv: Fix struct hv_message_header ordering
Message-ID: <20210729165638.f5idr2ag3pdbpd6u@liuwe-devbox-debian-v2>
References: <20210729133702.11383-1-sidcha@amazon.de>
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 <20210729140705.wj5tokeq6lkxm2yy@liuwe-devbox-debian-v2>
 <20210729142652.GA25242@uc8bbc9586ea454.ant.amazon.com>
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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.

Wei.