[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] a quick question about _PAGE_GLOBAL flag in para virt mode
On Sun, Feb 15, 2009 at 02:26:13PM -0800, Jeremy Fitzhardinge wrote: > >why not set global bit for user kernel pages? I guess this is because > >when domain switchs, all tlb entries will still be flushed, so it's > >not necessary for user kernel pages. Is my understanding right? > > 64-bit Xen uses paging to protect the guest kernel from guest usermode, > and protect Xen from the guest kernel, and as a result has to do a cr3 > reload for any user->kernel switch (which is why it has to go via Xen). > We don't want kernel mappings to be visible to usermode, so they have to > only be in tlb while we're actually running in guest kernel mode; And here's a real example of what happens when you don't get this right: http://blogs.sun.com/levon/entry/xen_compatibility_with_solaris regards john _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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