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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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>

Jan



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