Date: Fri, 20 Dec 2013 17:23:46 -0500 From: John Baldwin <jhb@freebsd.org> To: Neel Natu <neelnatu@gmail.com> Cc: "freebsd-virtualization@freebsd.org" <virtualization@freebsd.org> Subject: Re: Panic starting a bhyve guest after resume Message-ID: <201312201723.46978.jhb@freebsd.org> In-Reply-To: <CAFgRE9HWMY_uBEawSSiXgGEiqNHV-gmWeeBoi3qe50YAt48_2w@mail.gmail.com> References: <201312121511.38608.jhb@freebsd.org> <201312131709.20264.jhb@freebsd.org> <CAFgRE9HWMY_uBEawSSiXgGEiqNHV-gmWeeBoi3qe50YAt48_2w@mail.gmail.com>
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On Friday, December 13, 2013 9:28:29 pm Neel Natu wrote: > Hi John, > > On Fri, Dec 13, 2013 at 2:09 PM, John Baldwin <jhb@freebsd.org> wrote: > > On Thursday, December 12, 2013 4:00:08 pm Neel Natu wrote: > >> Hi John, > >> > >> On Thu, Dec 12, 2013 at 12:11 PM, John Baldwin <jhb@freebsd.org> wrote: > >> > If I suspend and resume my laptop and then try to start a guest after the > >> > resume, I get an odd panic. It generates a privileged instruction fault (in > >> > kernel mode) for 'vmclear'. I've checked CR4 and it claims that VMXE is set. > >> > I dont have any other ideas off the top of my head on what I should be poking > >> > at? It looks like we read a bunch of MSRs in vmx_init(), but we don't write > >> > to them, and all vmx_enable() does on each CPU is set VMXE in CR4 from what I > >> > can tell. > >> > > >> > >> It also does a "vmxon" on each logical cpu which may also need to be > >> done after a resume. > > > > Ah, yes it does. That was sufficient both for starting a new guest after > > resume and even doing a suspend/resume while a guest was active (and the > > guest continued to run fine). I have a hacky patch for this. One, it > > includes both a suspend and resume hook for VMM, though for my testing I only > > needed a resume hook to invoke vmxon. Second, the name of vmx_resume2() > > is a total hack (because vmx_resume() was already taken. I think for now > > if I were to commit this, I'd just add the resme hook and maybe call the > > Intel method vmx_reset() or vmx_restore()? > > > > http://people.freebsd.org/~jhb/patches/bhyve_resume.patch > > > > There seems to be a race after the APs are restarted and before > 'vmm_resume_p()' where it would be problematic to execute a VMX > instruction. > > Perhaps we should enable VMX on each cpu before they return to the > interrupted code? I've updated the patch at the URL above to do just that. This also works in my testing. -- John Baldwin
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