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Re: [PATCH] hw/vfio: let readonly flag take effect for mmaped regions

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] hw/vfio: let readonly flag take effect for mmaped regions
Date: Tue, 31 Mar 2020 09:59:02 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0

On 3/27/20 5:17 PM, Paolo Bonzini wrote:
On 27/03/20 11:51, Philippe Mathieu-Daudé wrote:
   diff --git a/memory.c b/memory.c
index 601b749906..4b1071dc74 100644
--- a/memory.c
+++ b/memory.c
@@ -1313,6 +1313,9 @@ static void memory_region_ram_device_write(void
*opaque, hwaddr addr,
       MemoryRegion *mr = opaque;
         trace_memory_region_ram_device_write(get_cpu_index(), mr,
addr, data, size);
+    if (mr->readonly) {
+        return;
+    }

Shouldn't this be in memory_region_dispatch_write()?

No, in general you want memory regions to get writes, so that they
become for example a machine-check exception of some sorts.  However,
memory_region_ram_device_write should probably be changed to a
.write_with_attrs operation, so that it can return MEMTX_ERROR.

Please split this patch in 2, this (generic) hunk as first patch, then
the VFIO more specific change.

         switch (size) {
       case 1:

No need, I can just add my Acked-by for Alex to pick up the patch.

Having 2 different fix in 2 different patches helps when cherry-picking (bisecting, backporting...) and reverting. My 2 cents anyway.

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