[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 7/7] x86/pagewalk: Re-implement the pagetable walker
On 06/03/17 18:33, Andrew Cooper wrote: > On 06/03/17 18:28, George Dunlap wrote: >> On 27/02/17 14:03, Andrew Cooper wrote: >>> The existing pagetable walker has complicated return semantics, which >>> squeeze >>> multiple pieces of information into single integer. This would be fine if >>> the >>> information didn't overlap, but it does. >>> >>> Specifically, _PAGE_INVALID_BITS for 3-level guests alias _PAGE_PAGED and >>> _PAGE_SHARED. A guest which constructs a PTE with bits 52 or 53 set (the >>> start of the upper software-available range) will create a virtual address >>> which, when walked by Xen, tricks Xen into believing the frame is paged or >>> shared. This behaviour was introduced by XSA-173 (c/s 8b17648). >>> >>> It is also complicated to turn rc back into a normal pagefault error code. >>> Instead, change the calling semantics to return a boolean indicating >>> success, >>> and have the function accumulate a real pagefault error code as it goes >>> (including synthetic error codes, which do not alias hardware ones). This >>> requires an equivalent adjustment to map_domain_gfn(). >>> >>> Issues fixed: >>> * 2-level PSE36 superpages now return the correct translation. >>> * 2-level L2 superpages without CR0.PSE now return the correct translation. >>> * SMEP now inhibits a user instruction fetch even if NX isn't active. >>> * Supervisor writes without CR0.WP now set the leaf dirty bit. >>> * L4e._PAGE_GLOBAL is strictly reserved on AMD. >>> * 3-level l3 entries have all reserved bits checked. >>> * 3-level entries can no longer alias Xen's idea of paged or shared. >>> >>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> >> Andy, >> >> Have you got this in a tree somewhere? This doesn't seem to apply to >> staging, and I don't think I'm going to be able to give it a proper >> review without seeing the changes in-situ. (Or if you're close to >> reposting I'll wait for the repost.) > > I do have some bits an pieces (although I am some of your acks on the > earlier trivial patches.) Yeah, patch 4 it seems has been checked in already, and because of that I somehow got confused into thinking that more of them were checked in when I was going through the series. I'm about to head out tonight, but I'll give Acks or Reviews to the earlier ones tomorrow when I come back in. > This patch isn't going to change in any significant way, so here you go. > > http://xenbits.xen.org/gitweb/?p=people/andrewcoop/xen.git;a=shortlog;h=refs/heads/pagewalk-v1 Thanks. -George _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx https://lists.xen.org/xen-devel
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