* Re: [PATCH 6/13] KVM: memory slot management [not found] ` <200610271605.27600.arnd-r2nGTMty4D4@public.gmane.org> @ 2006-10-29 9:10 ` Avi Kivity 0 siblings, 0 replies; 2+ messages in thread From: Avi Kivity @ 2006-10-29 9:10 UTC (permalink / raw) To: Arnd Bergmann Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f, linux-kernel-u79uwXL29TY76Z2rM5mHXA Arnd Bergmann wrote: >> It can shoot not only its foot, but anything the monitor's uid has >> access to. Host files, the host network, other guests belonging to the >> user, etc. >> > > Yes, that's what I meant. It's obviously nicer if the guest can't do that, > but it's a tradeoff of the potential security impact against on how hard > it is to implement hiding the addresses you don't want your guest to see. > To put it into other words, do you want the optimal performance, or the > optimal security? > > Well, isolation is one of the most significant features of full virtualization, both for security and reliability. I don't think we can compromise that. >> It's worse than I thouht: tlb entries generated by guest accesses are >> tagged with the guest virtual address, to if you remove a guest >> physical/host virtual page you need to invalidate the entire guest tlb. >> > > Ok, so it's the HW's fault. They either copied bad or decided doing the > s390 approach was too expensive. > x86 tradition is to make all possible mistakes before getting a working solution. -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ^ permalink raw reply [flat|nested] 2+ messages in thread
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* Re: [PATCH 6/13] KVM: memory slot management [not found] ` <4542292C.3080409-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org> @ 2006-10-29 9:15 ` Avi Kivity 0 siblings, 0 replies; 2+ messages in thread From: Avi Kivity @ 2006-10-29 9:15 UTC (permalink / raw) To: Anthony Liguori Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f, linux-kernel-u79uwXL29TY76Z2rM5mHXA Anthony Liguori wrote: >> >> It's not about tlb entries. The shadow page tables collaples a GV -> >> HV -> HP double translation into a GV -> HP page table. When the >> Linux vm goes around evicting pages, it invalidates those mappings. >> >> There are two solutions possible: lock pages which participate in >> these translations (and their number can be large) or modify the >> Linux vm to consult a reverse mapping and remove the translations (in >> which case TLB entries need to be removed). >> > > If you locked pages that have active shadow mappings, you could then > use a secondary mechanism to invalidate existing mappings when necessary. > Yes. There are two needs: to propagate virtual machine activity to the host (by folding dirty and accessed bits from multiple shadow ptes into a single struct page), and to apply pressure from the vm to the guest (by invalidating all mappings of a given page). -- error compiling committee.c: too many arguments to function ------------------------------------------------------------------------- Using Tomcat but need to do more? Need to support web services, security? Get stuff done quickly with pre-integrated technology to make your job easier Download IBM WebSphere Application Server v.1.0.1 based on Apache Geronimo http://sel.as-us.falkag.net/sel?cmd=lnk&kid=120709&bid=263057&dat=121642 ^ permalink raw reply [flat|nested] 2+ messages in thread
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2006-10-29 9:10 ` [PATCH 6/13] KVM: memory slot management Avi Kivity
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