[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1 of 3] After preparing a page for page-in, allow immediate fill-in of the page contents
At 12:21 -0500 on 01 Dec (1322742072), Andres Lagar-Cavilla wrote: > xen/arch/x86/mm/mem_event.c | 2 +- > xen/arch/x86/mm/mem_paging.c | 2 +- > xen/arch/x86/mm/p2m.c | 32 ++++++++++++++++++++++++++++++-- > xen/include/asm-x86/p2m.h | 2 +- > xen/include/public/domctl.h | 8 ++++++-- > 5 files changed, 39 insertions(+), 7 deletions(-) > > > p2m_mem_paging_prep ensures that an mfn is backing the paged-out gfn, and > transitions to the next state in the paging state machine for that page. > Foreign mappings of the gfn will now succeed. This is the key idea, as > it allows the pager to now map the gfn and fill in its contents. > > Unfortunately, it also allows any other foreign mapper to map the gfn and read > its contents. This is particularly dangerous when the populate is launched > by a foreign mapper in the first place, which will be actively retrying the > map operation and might race with the pager. Qemu-dm being a prime example. > > Fix the race by allowing a buffer to be optionally passed in the prep > operation, and having the hypervisor memcpy from that buffer into the newly > prepped page before promoting the gfn type. > > Signed-off-by: Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx> Acked-by: Tim Deegan <tim@xxxxxxx> Once Olaf OKs the xenpaging change, this whole set can go in. Tim. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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