linux-kernel - Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 3 Sep 2012 16:57:45 +0200
From:	Sjur Brændeland <sjurbren@...il.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Amit Shah <amit.shah@...hat.com>, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Ohad Ben-Cohen <ohad@...ery.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation

Hi Michael,

> How does access to descriptors work in this setup?

When the ring is setup by remoteproc the descriptors are
also allocated using dma_alloc_coherent().

>> -static void free_buf(struct port_buffer *buf)
>> +/* Allcoate data buffer from DMA memory if requested */
>
> typo

Thanks.

>> +static inline void *
>> +alloc_databuf(struct virtio_device *vdev, size_t size, dma_addr_t *dma_handle,
>> +                gfp_t flag)
>>  {
>> -     kfree(buf->buf);
>> +#ifdef CONFIG_HAS_DMA
>> +     if (virtio_has_feature(vdev, VIRTIO_CONSOLE_F_DMA_MEM)) {
>> +             struct device *dev = &vdev->dev;
>> +             /*
>> +              * Allocate DMA memory from ancestors. Finding the ancestor
>> +              * is a bit quirky when DMA_MEMORY_INCLUDES_CHILDREN is not
>> +              * implemented.
>> +              */
>> +             dev = dev->parent ? dev->parent : dev;
>> +             dev = dev->parent ? dev->parent : dev;
>> +             return dma_alloc_coherent(dev, size, dma_handle, flag);
>> +     }
>> +#endif
>
> Are these ifdefs really needed? If DMA_MEM is set,
> can't we use dma_alloc_coherent
> unconditionally?

If an architecture do not support DMA you will get
a link error: "unknown symbol" for dma_alloc_coherent.

Regards,
Sjur
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/