RE: [Xen-devel] NMI delivery not correctly working

["Kaushik Barde" <Kaushik_Barde@xxxxxxxxxxx>]

Keir:

Processor disables calls to subsequent NMIs till it receives next IRET
instruction (via masking of maskable interrupts).
I guess, what I am not clear about is how a fully-virtualized guest
whould issue a IRET hypercall?

-Kaushik

-----Original Message-----
From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
[mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Keir Fraser
Sent: Tuesday, July 24, 2007 10:08 AM
To: Christoph Egger; xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] NMI delivery not correctly working

On 24/7/07 16:47, "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:

> I know, there is a line "current->nmi_masked = 0;" in do_iret() in
> xen/arch/x86/x86_(32|64)/traps.c, but this is actually never called
> after NMI delivery.

Guests *must* use the iret hypercall when returning from their NMI
handler.
This is giving a virtualised equivalent of the 'NMI-blocking' latch
implemented in x86 processors, which is reset by the IRET instruction.

 -- Keir


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