linux-kernel - Re: [PATCH v4 7/7] xen/arm: introduce GNTTABOP_cache

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Message-ID: <1413820211.29506.9.camel@citrix.com>
Date:	Mon, 20 Oct 2014 16:50:11 +0100
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
CC:	<xen-devel@...ts.xensource.com>, <konrad.wilk@...cle.com>,
	<david.vrabel@...rix.com>, <linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v4 7/7] xen/arm: introduce GNTTABOP_cache_flush

On Fri, 2014-10-10 at 12:51 +0100, Stefano Stabellini wrote:
> Introduce support for new hypercall GNTTABOP_cache_flush.
> Use it to perform cache flashing on pages used for dma when necessary.
> 
> If GNTTABOP_cache_flush is supported by the hypervisor, we don't need to
> bounce dma map operations that involve foreign grants and non-coherent
> devices.
> 
> Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
> 
> ---
> 
> Changes in v4:
> - add comment;
> - avoid bouncing dma map operations that involve foreign grants and
> non-coherent devices if GNTTABOP_cache_flush is provided by Xen.
> 
> Changes in v3:
> - fix the cache maintenance op call to match what Linux does natively;
> - update the hypercall interface to match Xen.
> 
> Changes in v2:
> - update the hypercall interface to match Xen;
> - call the interface on a single page at a time.
> ---
>  arch/arm/xen/mm.c                   |   41 ++++++++++++++++++++++++++++++-----
>  include/xen/interface/grant_table.h |   19 ++++++++++++++++
>  2 files changed, 54 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
> index 0c2a75a..21db123 100644
> --- a/arch/arm/xen/mm.c
> +++ b/arch/arm/xen/mm.c
> @@ -11,6 +11,7 @@
>  #include <linux/swiotlb.h>
>  
>  #include <xen/xen.h>
> +#include <xen/interface/grant_table.h>
>  #include <xen/interface/memory.h>
>  #include <xen/swiotlb-xen.h>
>  
> @@ -44,6 +45,8 @@ static inline void *kmap_high_get(struct page *page)
>  static inline void kunmap_high(struct page *page) {}
>  #endif
>  
> +static bool hypercall_flush = false;

Would be nice to include the word "cache" (or at least cflush) in this.

> -arch_initcall(xen_mm_init);
> +arch_initcall(xen_mm_init)

I think this is stray?

Acked-by: Ian Campbell <ian.campbell@...rix.com>

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