Re: [Xen-devel] [RFC for-4.8 v2 1/7] xen/arm: Add MATTR_MEM_NC for normal non-cacheable memory

["Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>]

On Mon, Jun 06, 2016 at 06:23:47PM +0100, Julien Grall wrote:
> Hi Edgar,
> 
> On 03/06/16 14:29, Edgar E. Iglesias wrote:
> >From: "Edgar E. Iglesias" <edgar.iglesias@xxxxxxxxxx>
> >
> >Add the MATTR_MEM_NC macro describing normal non-cacheable memory.
> >
> >Signed-off-by: Edgar E. Iglesias <edgar.iglesias@xxxxxxxxxx>
> >---
> >  xen/arch/arm/p2m.c         | 1 +
> >  xen/include/asm-arm/page.h | 1 +
> >  2 files changed, 2 insertions(+)
> >
> >diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> >index 838d004..0f1e1b1 100644
> >--- a/xen/arch/arm/p2m.c
> >+++ b/xen/arch/arm/p2m.c
> >@@ -343,6 +343,7 @@ static lpae_t mfn_to_p2m_entry(unsigned long mfn, 
> >unsigned int mattr,
> >          e.p2m.sh = LPAE_SH_INNER;
> >          break;
> >
> >+    case MATTR_MEM_NC:
> 
> I would add a comment here to explain why non-cacheable memory should always
> be outer-shareable (see DDI 0406C.b B3-1376 to 1377).
> 
> For ideas on what to write, see mfn_to_xen_entry in include/asm-arm/page.h

Thanks, I've added a comment for v3.

CHeers,
Edgar


> 
> >      case MATTR_DEV:
> >          e.p2m.sh = LPAE_SH_OUTER;
> >          break;
> >diff --git a/xen/include/asm-arm/page.h b/xen/include/asm-arm/page.h
> >index a94e978..45d2e2c 100644
> >--- a/xen/include/asm-arm/page.h
> >+++ b/xen/include/asm-arm/page.h
> >@@ -73,6 +73,7 @@
> >   *
> >   */
> >  #define MATTR_DEV     0x1
> >+#define MATTR_MEM_NC  0x5
> >  #define MATTR_MEM     0xf
> >
> >  /* Flags for get_page_from_gva, gvirt_to_maddr etc */
> >
> 
> Regards,
> 
> -- 
> Julien Grall

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