Re: [Xen-devel] [PATCH v6 2/2] add a new p2m type - p2m_mmio_write_dm

[Tim Deegan <tim@xxxxxxx>]

At 11:55 +0800 on 06 Dec (1417863337), Yu Zhang wrote:
> From: Yu Zhang <yu.c.zhang@xxxxxxxxx>
> 
> A new p2m type, p2m_mmio_write_dm, is added to trap and emulate
> the write operations on GPU's page tables. Handling of this new
> p2m type are similar with existing p2m_ram_ro in most condition
> checks, with only difference on final policy of emulation vs. drop.
> For p2m_ram_ro types, write operations will not trigger the device
> model, and will be discarded later in __hvm_copy(); while for the
> p2m_mmio_write_dm type pages, writes will go to the device model
> via ioreq-server.
> 
> Signed-off-by: Yu Zhang <yu.c.zhang@xxxxxxxxxxxxxxx>
> Signed-off-by: Wei Ye <wei.ye@xxxxxxxxx>

Sorry not to have seen this before, but it looks like the new type isn't
handled in the shadow-pagetable code.  I think you need this as well:

diff --git a/xen/arch/x86/mm/shadow/multi.c b/xen/arch/x86/mm/shadow/multi.c
index 225290e..58c0cca 100644
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -3181,7 +3181,8 @@ static int sh_page_fault(struct vcpu *v,
     }
 
     /* Need to hand off device-model MMIO to the device model */
-    if ( p2mt == p2m_mmio_dm ) 
+    if ( p2mt == p2m_mmio_dm
+         || p2mt == p2m_mmio_readonly && ft == ft_demand_write )
     {
         gpa = guest_walk_to_gpa(&gw);
         goto mmio;

With that hunk added, you can add

Reviewed-by: Tim Deegan <tim@xxxxxxx>

Tim.

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