From: linux@arm.linux.org.uk (Russell King - ARM Linux)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v4 12/13] ARM: KVM: vgic: reduce the number of vcpu kick
Date: Wed, 5 Dec 2012 15:55:41 +0000 [thread overview]
Message-ID: <20121205155541.GP14363@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <50BF4EC8.1050902@arm.com>
On Wed, Dec 05, 2012 at 01:40:24PM +0000, Marc Zyngier wrote:
> Admittedly, the whole sequence should be rewritten to be clearer. What
> it does is "If we're running a guest and there is no active interrupt,
> then kick the guest".
On the whole this entire thing should be written clearer; from the
explanations you've given it seems that the only reason this code works
is because you're relying on several behaviours all coming together to
achieve the right result - which makes for fragile code.
You're partly relying on atomic types to ensure that the increment and
decrement happen exclusively. You're then relying on a combination of
IRQ protection and cmpxchg() to ensure that the non-atomic read of the
atomic type won't be a problem.
This doesn't inspire confidence, and I have big concerns over whether
this code will still be understandable in a number of years time.
And I still wonder how safe this is even with your explanations. IRQ
disabling only works for the local CPU core so I still have questions
over this wrt a SMP host OS.
next prev parent reply other threads:[~2012-12-05 15:55 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-10 15:44 [PATCH v4 00/13] KVM/ARM vGIC support Christoffer Dall
2012-11-10 15:44 ` [PATCH v4 01/13] KVM: ARM: Introduce KVM_SET_DEVICE_ADDRESS ioctl Christoffer Dall
2012-11-10 15:44 ` [PATCH v4 02/13] ARM: KVM: Keep track of currently running vcpus Christoffer Dall
2012-11-28 12:47 ` Will Deacon
2012-11-28 13:15 ` Marc Zyngier
2012-11-30 22:39 ` Christoffer Dall
2012-11-10 15:44 ` [PATCH v4 03/13] ARM: KVM: Initial VGIC infrastructure support Christoffer Dall
2012-11-28 12:49 ` Will Deacon
2012-11-28 13:09 ` Marc Zyngier
2012-11-28 14:13 ` Will Deacon
2012-12-01 2:19 ` Christoffer Dall
2012-11-10 15:44 ` [PATCH v4 04/13] ARM: KVM: Initial VGIC MMIO support code Christoffer Dall
2012-11-12 8:54 ` Dong Aisheng
2012-11-13 13:32 ` Christoffer Dall
2012-11-28 13:09 ` Will Deacon
2012-11-28 13:44 ` Marc Zyngier
2012-11-10 15:44 ` [PATCH v4 05/13] ARM: KVM: VGIC accept vcpu and dist base addresses from user space Christoffer Dall
2012-11-12 8:56 ` Dong Aisheng
2012-11-13 13:35 ` Christoffer Dall
2012-11-28 13:11 ` Will Deacon
2012-11-28 13:22 ` [kvmarm] " Marc Zyngier
2012-12-01 2:52 ` Christoffer Dall
2012-12-01 15:57 ` Christoffer Dall
2012-12-03 10:40 ` Will Deacon
2012-11-10 15:44 ` [PATCH v4 06/13] ARM: KVM: VGIC distributor handling Christoffer Dall
2012-11-12 9:29 ` Dong Aisheng
2012-11-13 13:38 ` Christoffer Dall
2012-11-28 13:21 ` Will Deacon
2012-11-28 14:35 ` Marc Zyngier
2012-11-10 15:45 ` [PATCH v4 07/13] ARM: KVM: VGIC virtual CPU interface management Christoffer Dall
2012-12-03 13:23 ` Will Deacon
2012-12-03 14:11 ` Marc Zyngier
2012-12-03 14:34 ` Will Deacon
2012-12-03 15:24 ` Marc Zyngier
2012-12-03 14:54 ` Christoffer Dall
2012-11-10 15:45 ` [PATCH v4 08/13] ARM: KVM: vgic: retire queued, disabled interrupts Christoffer Dall
2012-12-03 13:24 ` Will Deacon
2012-11-10 15:45 ` [PATCH v4 09/13] ARM: KVM: VGIC interrupt injection Christoffer Dall
2012-12-03 13:25 ` Will Deacon
2012-12-03 14:21 ` Marc Zyngier
2012-12-03 14:58 ` Christoffer Dall
2012-12-03 19:13 ` Christoffer Dall
2012-12-03 19:22 ` Marc Zyngier
2012-11-10 15:45 ` [PATCH v4 10/13] ARM: KVM: VGIC control interface world switch Christoffer Dall
2012-12-03 13:31 ` Will Deacon
2012-12-03 14:26 ` Marc Zyngier
2012-11-10 15:45 ` [PATCH v4 11/13] ARM: KVM: VGIC initialisation code Christoffer Dall
2012-12-05 10:43 ` Will Deacon
2012-11-10 15:45 ` [PATCH v4 12/13] ARM: KVM: vgic: reduce the number of vcpu kick Christoffer Dall
2012-12-05 10:43 ` Will Deacon
2012-12-05 10:58 ` Russell King - ARM Linux
2012-12-05 12:17 ` Marc Zyngier
2012-12-05 12:29 ` Russell King - ARM Linux
2012-12-05 13:40 ` Marc Zyngier
2012-12-05 15:55 ` Russell King - ARM Linux [this message]
2012-12-05 11:16 ` Russell King - ARM Linux
2012-11-10 15:45 ` [PATCH v4 13/13] ARM: KVM: Add VGIC configuration option Christoffer Dall
2012-11-10 19:52 ` Sergei Shtylyov
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