Re: [Xen-devel] [PATCH V3] x86/vm_event: block interrupt injection for sync vm_events

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Razvan Cojocaru [mailto:rcojocaru@xxxxxxxxxxxxxxx]
> Sent: Friday, December 14, 2018 7:50 PM
> 
> Block interrupts (in vmx_intr_assist()) for the duration of
> processing a sync vm_event (similarly to the strategy
> currently used for single-stepping). Otherwise, attempting
> to emulate an instruction when requested by a vm_event
> reply may legitimately need to call e.g.
> hvm_inject_page_fault(), which then overwrites the active
> interrupt in the VMCS.
> 
> The sync vm_event handling path on x86/VMX is (roughly):
> monitor_traps() -> process vm_event -> vmx_intr_assist()
> (possibly writing VM_ENTRY_INTR_INFO) ->
> hvm_vm_event_do_resume() -> hvm_emulate_one_vm_event()
> (possibly overwriting the VM_ENTRY_INTR_INFO value).
> 
> This patch may also be helpful for the future removal
> of may_defer in hvm_set_cr{0,3,4} and hvm_set_msr().
> 
> Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
> 

Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>

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