From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pavel Fedin Subject: RE: [PATCH v2 01/15] KVM: arm/arm64: VGIC: don't track used LRs in the distributor Date: Fri, 02 Oct 2015 12:55:05 +0300 Message-ID: <00cb01d0fcf8$6a906000$3fb12000$@samsung.com> References: <1436538111-4294-1-git-send-email-andre.przywara@arm.com> <1436538111-4294-2-git-send-email-andre.przywara@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org To: 'Andre Przywara' , marc.zyngier@arm.com, christoffer.dall@linaro.org, kvmarm@lists.cs.columbia.edu Return-path: In-reply-to: <1436538111-4294-2-git-send-email-andre.przywara@arm.com> Content-language: ru List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org Hello! One more concern. > Currently we track which IRQ has been mapped to which VGIC list > register and also have to synchronize both. We used to do this > to hold some extra state (for instance the active bit). > It turns out that this extra state in the LRs is no longer needed and > this extra tracking causes some pain later. Returning to the beginning, can you explain, what kind of pain exactly does it bring? For some reasons here i had to keep all this tracking mechanism, and modified your patchset. I see no significant problems, except memory usage. I have to allocate vgic_irq_lr_map large enough to hold indexes up to 16384, and indexes from dist->nr_irqs to 8192 appear to be not used. Since the map itself is actually used only for piggy-back optimization, it is possible to easily get rid of it using for_each_set_bit(lr, vgic_cpu->lr_used, vgic->nr_lr) iteration instead. The rest of mechanism will work as it is, there's no need to remove the state tracking bitmap and optimization itself. I am currently testing this approach and preparing my alternative patch for upstreaming. Kind regards, Pavel Fedin Expert Engineer Samsung Electronics Research center Russia