On 09/05/2019 17:19, Mathieu Tarral wrote: > Le mardi, mai 7, 2019 2:01 PM, Mathieu Tarral <mathieu.tar...@protonmail.com> > a écrit : > >>> Given how many EPT flushing bugs I've already found in this area, I >>> wouldn't be surprised if there are further ones lurking. If it is an EPT >>> flushing bug, this delta should make it go away, but it will come with a >>> hefty perf hit. >>> >>> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c >>> index 283eb7b..019333d 100644 >>> --- a/xen/arch/x86/hvm/vmx/vmx.c >>> +++ b/xen/arch/x86/hvm/vmx/vmx.c >>> @@ -4285,9 +4285,7 @@ bool vmx_vmenter_helper(const struct cpu_user_regs >>> *regs) >>> } >>> } >>> >>> - if ( inv ) >>> - __invept(inv == 1 ? INVEPT_SINGLE_CONTEXT : INVEPT_ALL_CONTEXT, >>> - inv == 1 ? single->eptp : 0); >>> + __invept(INVEPT_ALL_CONTEXT, 0); >>> } >>> >>> out: >> I can give this a try, and see if it resolves the problem ! > Just tested, on Xen 4.12.0, and the bug is still here. > Windows 7 is having BSODs with 4 VCPUs. > I didn't noticed a hefty performance impact though. > > Do we have other caches to invalidate ? > Something else that i should test ? > > I don't feel comfortable digging into Xen's code, especially for something as > complicated as page table and memory management, > increased by the complexity of altp2m. > What i can do however, is test your ideas and patches and report the > information I can gather on this issue. > > Note: I tested with the latest commits on Drakvuf/master, especially: > "Add a VM pause for shadow copy refresh operation" > https://github.com/tklengyel/drakvuf/pull/626 > > @tamas, did you made this patch to fix these kind of race conditions issue > that i'm reporting ? > Or was it totally unrelated ?
With the above change in place and BSODs still happening, I'm fairly convinced that it not a TLB flushing issue. Therefore, the conclusion to draw is that it is a logical bug somewhere. First of all - ensure you are using up-to-date microcode. The number of errata which have been discovered by people associated with the Xen community is large. The microcode is available from https://github.com/intel/Intel-Linux-Processor-Microcode-Data-Files/ and https://andrewcoop-xen.readthedocs.io/en/latest/admin-guide/microcode-loading.html is some documentation I prepared earlier. Beyond that, I think it would help to know exactly how libvmi is manipulating the guest. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
