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

On 12/25/18 4:29 AM, Tian, Kevin wrote:
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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