[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Grant Tables & mm.c
I was looking at the user space grant tables but i did not find any code calling the function "remap_pfn_range" to map the kmalloc ed allocated memory into user space. What could be the reason?? Or am i missing something Thanks Mark. ----- Original Message ---- From: Mark Williamson <mark.williamson@xxxxxxxxxxxx> To: Koripella Srinivas <talkwithsrinivas@xxxxxxxxxxx> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx Sent: Friday, 6 July, 2007 9:55:48 AM Subject: Re: [Xen-devel] Grant Tables & mm.c > " Linux tends to zap userspace page mappings quite cheerfully > unless you do something to stop it, could this be your problem?" > > What does this mean exactly?? Linux "zaps" mappings when it removes them from pagetables. Really this corresponds to zeroing a pte corresponding to that mapping. Unless you do something to stop the Linux mm system from treating the grant table mappins like "normal" RAM, it will eventually want to simply zero them. This will break for grant mappings, since it is not a permitted means of unmapping granted memory. > Any way i can prevent it from happening? It depends on what you're trying to do... Have you looked at the userspace grantables driver in our Linux tree? This provides a device for mapping granted memory safely into userspace, handling cleanup correctly. Even if that's not directly useful, maybe you can find some code in there that'll help you. Cheers, Mark -- Dave: Just a question. What use is a unicyle with no seat? And no pedals! Mark: To answer a question with a question: What use is a skateboard? Dave: Skateboards have wheels. Mark: My wheel has a wheel! Hereʼs a new way to find what you're looking for - Yahoo! Answers _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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