From mboxrd@z Thu Jan  1 00:00:00 1970
From: stefanha@gmail.com (Stefan Hajnoczi)
Date: Tue, 6 Oct 2015 09:40:42 +0100
Subject: [Qemu-devel] [PATCH v3 1/4] firmware: introduce sysfs driver for
	QEMU's fw_cfg device
In-Reply-To: <1443914889-9619-2-git-send-email-somlo@cmu.edu>
References: <1443914889-9619-1-git-send-email-somlo@cmu.edu>
	<1443914889-9619-2-git-send-email-somlo@cmu.edu>
Message-ID: <20151006084042.GC19089@stefanha-thinkpad>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

On Sat, Oct 03, 2015 at 07:28:06PM -0400, Gabriel L. Somlo wrote:
> +/* read chunk of given fw_cfg blob (caller responsible for sanity-check) */
> +static inline void fw_cfg_read_blob(u16 key,
> +				    void *buf, loff_t pos, size_t count)
> +{
> +	mutex_lock(&fw_cfg_dev_lock);
> +	iowrite16(fw_cfg_sel_endianness(key), fw_cfg_reg_ctrl);
> +	while (pos-- > 0)
> +		ioread8(fw_cfg_reg_data);
> +	ioread8_rep(fw_cfg_reg_data, buf, count);
> +	mutex_unlock(&fw_cfg_dev_lock);
> +}

Have you had a chance to play with Marc Mari's fw_cfg DMA interface
patches?  They should make this operation much faster.

https://www.mail-archive.com/qemu-devel at nongnu.org/msg325541.html

Stefan