linux-kernel - Re: [Qemu-devel] [PATCH v3 1/4] firmware: introduce sysfs driver for QEMU's fw

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Date:	Tue, 6 Oct 2015 09:40:42 +0100
From:	Stefan Hajnoczi <stefanha@...il.com>
To:	"Gabriel L. Somlo" <somlo@....edu>
Cc:	gregkh@...uxfoundation.org, paul@...an.com, galak@...eaurora.org,
	will.deacon@....com, agross@...eaurora.org, mark.rutland@....com,
	zajec5@...il.com, hanjun.guo@...aro.org, catalin.marinas@....com,
	linux-api@...r.kernel.org, linux-kernel@...r.kernel.org,
	peter.maydell@...aro.org, matt.fleming@...el.com, mst@...hat.com,
	jordan.l.justen@...el.com, kernelnewbies@...nelnewbies.org,
	qemu-devel@...gnu.org, leif.lindholm@...aro.org,
	ard.biesheuvel@...aro.org, kraxel@...hat.com, pbonzini@...hat.com,
	lersek@...hat.com
Subject: Re: [Qemu-devel] [PATCH v3 1/4] firmware: introduce sysfs driver for
 QEMU's fw_cfg device

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@nongnu.org/msg325541.html

Stefan
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