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Message-ID: <46000C7E.4070001@goop.org>
Date: Tue, 20 Mar 2007 09:31:58 -0700
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
CC: "Eric W. Biederman" <ebiederm@...ssion.com>,
Zachary Amsden <zach@...are.com>,
Rusty Russell <rusty@...tcorp.com.au>, Andi Kleen <ak@....de>,
David Miller <davem@...emloft.net>, mingo@...e.hu,
akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
virtualization@...ts.osdl.org, xen-devel@...ts.xensource.com,
chrisw@...s-sol.org, anthony@...emonkey.ws, netdev@...r.kernel.org
Subject: Re: [patch 13/26] Xen-paravirt_ops: Consistently wrap paravirt ops
callsites to make them patchable
Linus Torvalds wrote:
> On Tue, 20 Mar 2007, Eric W. Biederman wrote:
>
>> If that is the case. In the normal kernel what would
>> the "the oops, we got an interrupt code do?"
>> I assume it would leave interrupts disabled when it returns?
>> Like we currently do with the delayed disable of normal interrupts?
>>
>
> Yeah, disable interrupts, and set a flag that the fake "sti" can test, and
> just return without doing anything.
>
> (You may or may not also need to do extra work to Ack the hardware
> interrupt etc, which may be irq-controller specific. Once the CPU has
> accepted the interrupt, you may not be able to just leave it dangling)
>
So it would be something like:
pda.intr_mask = 1; /* disable interrupts */
...
pda.intr_mask = 0; /* enable interrupts */
if (xchg(&pda.intr_pending, 0)) /* check pending */
asm("sti"); /* was pending; isr left cpu interrupts masked */
and in the interrupt handler:
if (pda.intr_mask) {
pda.intr_pending = 1;
regs->eflags &= ~IF;
maybe_ack_interrupt_controller();
iret
}
?
J
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