linux-kernel - Re: [kvm-devel] Notifier for Externally Mapped Memory (EMM) V1

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Message-ID: <47CF8B31.6040001@qumranet.com>
Date:	Thu, 06 Mar 2008 08:12:01 +0200
From:	Avi Kivity <avi@...ranet.com>
To:	Christoph Lameter <clameter@....com>
CC:	akpm@...ux-foundation.org, Nick Piggin <npiggin@...e.de>,
	Andrea Arcangeli <andrea@...ranet.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	kvm-devel@...ts.sourceforge.net, Jack Steiner <steiner@....com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Robin Holt <holt@....com>, general@...ts.openfabrics.org
Subject: Re: [kvm-devel] Notifier for Externally Mapped Memory (EMM) V1

Christoph Lameter wrote:
>  
>  /*
> + * Notifier for devices establishing their own references to Linux
> + * kernel pages in addition to the regular mapping via page
> + * table and rmap. The notifier allows the device to drop the mapping
> + * when the VM removes references to pages.
> + */
> +enum emm_operation {
> +	emm_release,		/* Process existing, */
> +	emm_invalidate_start,	/* Before the VM unmaps pages */
> +	emm_invalidate_end,	/* After the VM unmapped pages */
> +	emm_referenced		/* Check if a range was referenced */
> +};
>   

Check and clear


btw, a similar test and clear dirty would be useful as well, no?

> +
> +struct emm_notifier {
> +	int (*callback)(struct emm_notifier *e, struct mm_struct *mm,
> +		enum emm_operation op,
> +		unsigned long start, unsigned long end);
> +	struct emm_notifier *next;
> +};
> +
>   

It is cleaner for the user to specify individual callbacks instead of 
having a switch.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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