From patchwork Fri Aug 3 10:51:05 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [6/7] exec.c: Use subpages for large unaligned mappings Date: Fri, 03 Aug 2012 00:51:05 -0000 From: Stefan Hajnoczi X-Patchwork-Id: 174978 Message-Id: <1343991066-9814-7-git-send-email-stefanha@linux.vnet.ibm.com> To: Anthony Liguori Cc: qemu-devel@nongnu.org, Stefan Hajnoczi , Tyler Hall From: Tyler Hall Registering a multi-page memory region that is non-page-aligned results in a subpage from the start to the page boundary, some number of full pages, and possibly another subpage from the last page boundary to the end. The full pages will have a value for offset_within_region that is not a multiple of TARGET_PAGE_SIZE. Accesses through softmmu are unable to handle this and will segfault. Handling full pages through subpages is not optimal, but only non-page-aligned mappings take the penalty. Signed-off-by: Tyler Hall Reviewed-by: Peter Maydell Reviewed-by: Avi Kivity Signed-off-by: Stefan Hajnoczi --- exec.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/exec.c b/exec.c index 27b100c..e6ac3e7 100644 --- a/exec.c +++ b/exec.c @@ -2305,10 +2305,15 @@ void cpu_register_physical_memory_log(MemoryRegionSection *section, remain.offset_within_address_space += now.size; remain.offset_within_region += now.size; } - now = remain; - now.size &= TARGET_PAGE_MASK; - if (now.size) { - register_multipage(&now); + while (remain.size >= TARGET_PAGE_SIZE) { + now = remain; + if (remain.offset_within_region & ~TARGET_PAGE_MASK) { + now.size = TARGET_PAGE_SIZE; + register_subpage(&now); + } else { + now.size &= TARGET_PAGE_MASK; + register_multipage(&now); + } remain.size -= now.size; remain.offset_within_address_space += now.size; remain.offset_within_region += now.size;