Re: [Xen-devel] [PATCH for-4.12 V4] x86/altp2m: fix HVMOP_altp2m_set_domain_state race

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 2/12/19 2:57 PM, Jan Beulich wrote:
> > > > On 12.02.19 at 12:42, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> > HVMOP_altp2m_set_domain_state does not domain_pause(), presumably
> > on purpose (as it was originally supposed to cater to a in-guest
> > agent, and a domain pausing itself is not a good idea).
> >
> > This can lead to domain crashes in the vmx_vmexit_handler() code
> > that checks if the guest has the ability to switch EPTP without an
> > exit. That code can __vmread() the host p2m's EPT_POINTER
> > (before HVMOP_altp2m_set_domain_state "for_each_vcpu()" has a
> > chance to run altp2m_vcpu_initialise(), but after
> > d->arch.altp2m_active is set).
> >
> > This patch reorganizes the code so that d->arch.altp2m_active
> > is set to true only after all the init work has been done, and
> > to false before the uninit work begins. This required adding
> > a new bool parameter altp2m_vcpu_update_p2m(), which relied
> > on d->arch.altp2m_active being set before it's called.
> >
> > While at it, I've changed a couple of bool_t's to bool's.
> >
> > Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> FTR - this looks okay to me now. But I don't feel qualified to
> give an R-b, so just for the parts where it's applicable
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Thanks for the ack and the help!


Razvan

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