From: Christoph Hellwig <hch@infradead.org>
To: Sherry Sun <sherry.sun@nxp.com>
Cc: Christoph Hellwig <hch@infradead.org>,
"sudeep.dutt@intel.com" <sudeep.dutt@intel.com>,
"ashutosh.dixit@intel.com" <ashutosh.dixit@intel.com>,
"arnd@arndb.de" <arnd@arndb.de>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"wang.yi59@zte.com.cn" <wang.yi59@zte.com.cn>,
"huang.zijiang@zte.com.cn" <huang.zijiang@zte.com.cn>,
"rikard.falkeborn@gmail.com" <rikard.falkeborn@gmail.com>,
"lee.jones@linaro.org" <lee.jones@linaro.org>,
"mst@redhat.com" <mst@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH 1/5] misc: vop: change the way of allocating vring for noncoherent platform
Date: Mon, 28 Sep 2020 07:09:04 +0100 [thread overview]
Message-ID: <20200928060904.GA9387@infradead.org> (raw)
In-Reply-To: <VI1PR04MB4960DC1E64D65634FE76C7AA92340@VI1PR04MB4960.eurprd04.prod.outlook.com>
On Sun, Sep 27, 2020 at 07:58:29AM +0000, Sherry Sun wrote:
> Thanks for your reply.
> Can you explain why we cannot use the API and header above in drivers?
> And do you know if there are any APIs that could replace this to check the device hardware dma coherent support?
If your treat the memory as if it is coherent with device access you
should always use dma_alloc_coherent. The whole point of the DMA API
is to abstract such differences away.
> >
> > > + vdev->vvr[i].vrh.vring.used =
> > > + (void __force *)vpdev->hw_ops->remap(
> >
> > And you must not use __force casts without a comment explanation why
> > they are safe.
>
> Here is the original code, I moved the original code into the if() without change it.
> But I think this is because vpdev->hw_ops->remap() return type is void __iomem *, but vring.used need type void *.
> Maybe this is a workaround for Intel MIC platform, as it reassigns the used ring on the EP side.
Well, we'll need to figure out what is going on here, and blind casts to
and from __iomem are dangerous.
next prev parent reply other threads:[~2020-09-28 6:09 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-25 7:26 [PATCH 0/5] Add noncoherent platform support for vop driver Sherry Sun
2020-09-25 7:26 ` [PATCH 1/5] misc: vop: change the way of allocating vring for noncoherent platform Sherry Sun
2020-09-25 12:16 ` Greg KH
2020-09-27 7:06 ` Sherry Sun
2020-09-26 7:50 ` Christoph Hellwig
2020-09-27 7:58 ` Sherry Sun
2020-09-28 6:09 ` Christoph Hellwig [this message]
2020-09-28 10:10 ` Sherry Sun
2020-09-25 7:26 ` [PATCH 2/5] misc: vop: change the way of allocating used ring Sherry Sun
2020-09-25 7:26 ` [PATCH 3/5] misc: vop: simply return the saved dma address instead of virt_to_phys Sherry Sun
2020-09-25 12:17 ` Greg KH
2020-09-27 7:23 ` Sherry Sun
2020-09-25 7:26 ` [PATCH 4/5] misc: vop: set VIRTIO_F_ACCESS_PLATFORM for nocoherent platform Sherry Sun
2020-09-25 12:16 ` Greg KH
2020-09-27 7:20 ` Sherry Sun
2020-09-26 7:51 ` Christoph Hellwig
2020-09-27 8:05 ` Sherry Sun
2020-09-28 6:09 ` Christoph Hellwig
2020-09-28 9:57 ` Sherry Sun
2020-09-25 7:26 ` [PATCH 5/5] misc: vop: mapping kernel memory to user space as noncached Sherry Sun
2020-09-25 11:25 ` [PATCH 0/5] Add noncoherent platform support for vop driver Arnd Bergmann
2020-09-27 5:07 ` Sherry Sun
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