Re: [Xen-devel] [PATCH v8 2/4] x86/hvm: Treat non-instruction fetch nested page faults also as read violations

[Tim Deegan <tim@xxxxxxx>]

At 15:40 +0200 on 19 Aug (1408459219), Tamas K Lengyel wrote:
> As pointed out by Jan Beulich in 
> http://lists.xen.org/archives/html/xen-devel/2014-08/msg01269.html: 
> "Read-modify-write instructions absolutely need to be treated as read 
> accesses, yet hardware doesn't guarantee to tell us so (they may surface as 
> just write accesses)." This patch addresses the issue in both the VMX and the 
> SVM side.
> 
> VMX: Treat all write data access violations also as read violations (in 
> addition to those that were already reported as read violations).
> SVM: Refine the meaning of read data access violations to distinguish between 
> read/write and instruction fetch access violations.
> 
> With this patch both VMX and SVM specific nested page fault handling code 
> reports violations the same way, thus abstracting the hardware specific 
> behaviour from the layers above.
> 
> Suggested-by: Jan Beulich <JBeulich@xxxxxxxx>
> Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxxxxx>
> Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>

Reviewed-by: Tim Deegan <tim@xxxxxxx>

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