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From: Andrii Anisov <andrii.anisov@gmail.com>
To: Julien Grall <julien.grall@arm.com>, xen-devel@lists.xenproject.org
Cc: Andre Przywara <andre.przywara@arm.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Andrii Anisov <andrii_anisov@epam.com>
Subject: Re: [PATCH v2] gic: drop interrupts enabling on interrupts processing
Date: Thu, 30 May 2019 19:12:21 +0300	[thread overview]
Message-ID: <c0de5da0-9986-ea97-b7d3-6902bd789c19@gmail.com> (raw)
In-Reply-To: <f0e27dd4-fc59-05d8-e910-b63c0d398c00@arm.com>



On 29.05.19 18:32, Julien Grall wrote:
> It would have been nice to at least fix up the commit message with the typoes (and rewording) I mentioned in my previous e-mail.
> Your commit message needs to explained why this is fine to keep the interrupt masked a bit longer. I wrote the explanation in my previous e-mail so you can borrow the rationale from there.
xen/arm: gic: Defer the decision to unmask interrupts to do_{LPI, IRQ}()

Having irqs enabled here leaves a room for trapping and going through the trap
path again if we have a new guest interrupt arrived (even with the same or
lower priority, after `desc->handler->end(desc)` in `do_IRQ()`).
Keeping interrupts disabled during guest interrupts processing allows as
avoiding excessive traps (and wasting cpu cycles for trap path) while the new
interrupts would be processed in the loop anyway. Processing guest interrupts by
the loop should not introduce significant additional latency because
vgic_inject_irq(...) already masking the interrupts in most of the cases.


-- 
Sincerely,
Andrii Anisov.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

WARNING: multiple messages have this Message-ID (diff)
From: Andrii Anisov <andrii.anisov@gmail.com>
To: Julien Grall <julien.grall@arm.com>, xen-devel@lists.xenproject.org
Cc: Andre Przywara <andre.przywara@arm.com>,
	Stefano Stabellini <sstabellini@kernel.org>,
	Andrii Anisov <andrii_anisov@epam.com>
Subject: Re: [Xen-devel] [PATCH v2] gic: drop interrupts enabling on interrupts processing
Date: Thu, 30 May 2019 19:12:21 +0300	[thread overview]
Message-ID: <c0de5da0-9986-ea97-b7d3-6902bd789c19@gmail.com> (raw)
Message-ID: <20190530161221.kAlraVbA2-mMtGSWbKRcB0NZQPDrbvVDOxS2wj3oxe0@z> (raw)
In-Reply-To: <f0e27dd4-fc59-05d8-e910-b63c0d398c00@arm.com>



On 29.05.19 18:32, Julien Grall wrote:
> It would have been nice to at least fix up the commit message with the typoes (and rewording) I mentioned in my previous e-mail.
> Your commit message needs to explained why this is fine to keep the interrupt masked a bit longer. I wrote the explanation in my previous e-mail so you can borrow the rationale from there.
xen/arm: gic: Defer the decision to unmask interrupts to do_{LPI, IRQ}()

Having irqs enabled here leaves a room for trapping and going through the trap
path again if we have a new guest interrupt arrived (even with the same or
lower priority, after `desc->handler->end(desc)` in `do_IRQ()`).
Keeping interrupts disabled during guest interrupts processing allows as
avoiding excessive traps (and wasting cpu cycles for trap path) while the new
interrupts would be processed in the loop anyway. Processing guest interrupts by
the loop should not introduce significant additional latency because
vgic_inject_irq(...) already masking the interrupts in most of the cases.


-- 
Sincerely,
Andrii Anisov.

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel

  reply	other threads:[~2019-05-30 16:12 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-27  9:29 [PATCH v2] gic: drop interrupts enabling on interrupts processing Andrii Anisov
2019-05-27  9:29 ` [Xen-devel] " Andrii Anisov
2019-05-28 17:07 ` Julien Grall
2019-05-28 17:07   ` [Xen-devel] " Julien Grall
2019-05-29 10:31   ` Andrii Anisov
2019-05-29 10:31     ` [Xen-devel] " Andrii Anisov
2019-05-29 15:32     ` Julien Grall
2019-05-29 15:32       ` [Xen-devel] " Julien Grall
2019-05-30 16:12       ` Andrii Anisov [this message]
2019-05-30 16:12         ` Andrii Anisov
2019-05-31 17:11         ` Julien Grall
2019-05-31 17:11           ` [Xen-devel] " Julien Grall
2019-05-31 20:08           ` Stefano Stabellini
2019-05-31 20:08             ` [Xen-devel] " Stefano Stabellini
2019-06-10 15:49           ` Andrii Anisov
2019-06-10 19:51             ` Julien Grall
2019-06-11  7:38               ` Andrii Anisov
2019-05-30 16:14       ` Andrii Anisov
2019-05-30 16:14         ` [Xen-devel] " Andrii Anisov
2019-05-31 17:16         ` Julien Grall
2019-05-31 17:16           ` [Xen-devel] " Julien Grall
2019-05-31 17:28           ` Andre Przywara
2019-05-31 17:28             ` [Xen-devel] " Andre Przywara
2019-05-31 17:25   ` Andre Przywara
2019-05-31 17:25     ` [Xen-devel] " Andre Przywara
2019-05-31 17:54     ` Julien Grall
2019-05-31 17:54       ` [Xen-devel] " Julien Grall

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