From patchwork Thu Jul 29 10:41:45 2010
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Subject: Re: [PATCH 1/2] Fix segfault in mmio subpage handling code.
Date: Thu, 29 Jul 2010 00:41:45 -0000
From: Gleb Natapov <gleb@redhat.com>
X-Patchwork-Id: 60205
Message-Id: <20100729104145.GA24773@redhat.com>
To: qemu-devel@nongnu.org
Cc: kvm@vger.kernel.org

Use this one instead.

On Wed, Jul 28, 2010 at 06:13:22PM +0300, Gleb Natapov wrote:
> It is possible that subpage mmio is registered over existing memory
> page. When this happens "memory" will have real memory address and not
> index into io_mem array so next access to the page will generate
> segfault. It is uncommon to have some part of a page to be accessed as
> memory and some as mmio, but qemu shouldn't crash even when guest does
> stupid things. So lets just pretend that the rest of the page is
> unassigned if guest configure part of the memory page as mmio.
> 
> Signed-off-by: Gleb Natapov <gleb@redhat.com>

---
Gleb.

diff --git a/exec.c b/exec.c
index 5e9a5b7..53483bc 100644
--- a/exec.c
+++ b/exec.c
@@ -3362,6 +3362,8 @@ static int subpage_register (subpage_t *mmio, uint32_t start, uint32_t end,
     printf("%s: %p start %08x end %08x idx %08x eidx %08x mem %ld\n", __func__,
            mmio, start, end, idx, eidx, memory);
 #endif
+    if ((memory & ~TARGET_PAGE_MASK) == IO_MEM_RAM)
+        memory = IO_MEM_UNASSIGNED;
     memory = (memory >> IO_MEM_SHIFT) & (IO_MEM_NB_ENTRIES - 1);
     for (; idx <= eidx; idx++) {
         mmio->sub_io_index[idx] = memory;