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From: Wei Hu <weh@microsoft.com>
To: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: RE: [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs.
Date: Wed, 5 Feb 2020 11:33:03 +0000	[thread overview]
Message-ID: <SG2P153MB038005492C6FE395B6523A8EBB020@SG2P153MB0380.APCP153.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20200205080733.GU11068@kadam>



> -----Original Message-----
> > Thanks for reporting this. Would you let me know how I can reproduce
> > this warning or Error message? The build on my side runs fine without such
> message.
> 
> Hm...  Sorry, I never publish this Smatch check.  I should do that.
> Anyway HCH explains the rules a bit in this email:
> 
> https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Flkml.or
> g%2Flkml%2F2019%2F6%2F17%2F155&amp;data=02%7C01%7Cweh%40micro
> soft.com%7Cff5687dc7bb648623d3708d7aa127a4b%7C72f988bf86f141af91a
> b2d7cd011db47%7C1%7C0%7C637164868648450097&amp;sdata=0%2B8Jwe
> 1A%2FtOW0LqF8t2hqymWuzZjVtUxBIKgMyOQdFc%3D&amp;reserved=0
> 

I see. This is virtual frame buffer device on Hyper-V. It would not get address from 
vmap or ioremap. On the other hand, if dma_alloc_coherent() returns address without
page backing, this driver will blow even without calling virt_to_phys. 

Dma_alloc_coherent() is the recommended interface to allocate large contiguous
physical memory, in which case this call is doing so. I think you can ignore this 
in your check.

Thanks,
Wei

      reply	other threads:[~2020-02-05 11:33 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-05  5:43 [bug report] video: hyperv: hyperv_fb: Use physical memory for fb on HyperV Gen 1 VMs Dan Carpenter
2020-02-05  7:21 ` Wei Hu
2020-02-05  8:07   ` Dan Carpenter
2020-02-05 11:33     ` Wei Hu [this message]

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