Re: [Xen-devel] [PATCH v3 for 4.10] x86/vpt: guarantee the return value of pt_update_irq() set in vIRR or PIR

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

> From: Gao, Chao
> Sent: Friday, October 20, 2017 8:35 AM
> 
> pt_update_irq() is expected to return the vector number of periodic
> timer interrupt, which should be set in vIRR of vlapic or in PIR.
> Otherwise it would trigger the assertion in vmx_intr_assist(), please
> seeing https://lists.xenproject.org/archives/html/xen-devel/2017-
> 10/msg00915.html.
> 
> But it fails to achieve that in the following two case:
> 1. hvm_isa_irq_assert() may not set the corresponding bit in vIRR for
> mask field of IOAPIC RTE is set. Please refer to the call tree
> vmx_intr_assist() -> pt_update_irq() -> hvm_isa_irq_assert() ->
> assert_irq() -> assert_gsi() -> vioapic_irq_positive_edge(). The patch
> checks whether the vector is set or not in vIRR of vlapic or PIR before
> returning.
> 
> 2. someone changes the vector field of IOAPIC RTE between asserting
> the irq and getting the vector of the irq, leading to setting the
> old vector number but returning a different vector number. This patch
> allows hvm_isa_irq_assert() to accept a callback which can get the
> interrupt vector with irq_lock held. Thus, no one can change the vector
> between the two operations.
> 
> BTW, the first argument of pi_test_and_set_pir() should be uint8_t
> and I take this chance to fix it.
> 
> Signed-off-by: Chao Gao <chao.gao@xxxxxxxxx>

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

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