[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] [RFC PATCH] xen: vmx: Use an INT 2 call to process real NMI's instead of self_nmi() in VMEXIT handler
On 13/11/12 12:05, Tim Deegan wrote: > At 11:47 +0000 on 13 Nov (1352807234), Tim Deegan wrote: >> At 11:38 +0000 on 13 Nov (1352806689), Jan Beulich wrote: >>>> diff -r 62885b3c34c8 -r ea756059a8da xen/arch/x86/hvm/vmx/vmx.c >>>> --- a/xen/arch/x86/hvm/vmx/vmx.c >>>> +++ b/xen/arch/x86/hvm/vmx/vmx.c >>>> @@ -2442,7 +2442,7 @@ void vmx_vmexit_handler(struct cpu_user_ >>>> (X86_EVENTTYPE_NMI << 8) ) >>>> goto exit_and_crash; >>>> HVMTRACE_0D(NMI); >>>> - self_nmi(); /* Real NMI, vector 2: normal processing. */ >>>> + asm("int $2"); /* Real NMI, vector 2: normal processing. */ >>> In any case - why can't you call do_nmi() directly from here? >> ... this is my doing. There used to be a call to do_nmi() here, but >> do_nmi() doesn't block NMIs, so you can't just call it here in case you >> get _another_ NMI while you're in the NMI handler. > Oh wait, I see -- you're saying that this (20059:76a65bf2aa4d) is wrong > because NMIs are indeed blocked, and have been since the VMEXIT. > > In that case, I agree that we should just run the NMI handler, but first > I would really like to know what _unblocks_ NMIs in this case. Any of > the things I can think of (the next vmenter, the next iret, ??) will > need some handling to make sure they actually happen before, say, we > take this CPU into the idle loop... > > Tim. The first experiment was to have self_nmi() wait until the NMI count for the current processor changed. This prevented the thousands of bounces in and out of non-root mode, but the enter delays fairly consistently in the millions of TSC ticks (a few milliseconds on the test box), which is a noticeable chunk of time. ~Andrew > > _______________________________________________ > Xen-devel mailing list > Xen-devel@xxxxxxxxxxxxx > http://lists.xen.org/xen-devel -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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