From mboxrd@z Thu Jan  1 00:00:00 1970
From: p.fedin@samsung.com (Pavel Fedin)
Date: Fri, 02 Oct 2015 15:39:44 +0300
Subject: [PATCH v2 01/15] KVM: arm/arm64: VGIC: don't track used LRs in the
 distributor
In-Reply-To: <560E5D2F.1000401@arm.com>
References: <1436538111-4294-1-git-send-email-andre.przywara@arm.com>
 <1436538111-4294-2-git-send-email-andre.przywara@arm.com>
 <00cb01d0fcf8$6a906000$3fb12000$@samsung.com> <560E5D2F.1000401@arm.com>
Message-ID: <00f301d0fd0f$6b21ac10$41650430$@samsung.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

 Hello!

> Can't you use the ELRSR bitmap instead? The idea of lr_used sounds like
> a moot optimization to me.

 This perfectly works on 4.2, but will break HW interrupt forwarding on 4.3. If you look at 4.3
__kvm_vgic_sync_hwstate(), you'll notice that for HW interrupts lr_used and elrsr_ptr will diverge
at this point, and this function actually brings them into sync. And it relies on lr_used for the
loop to operate correctly (no idea why we use "for" loop here with extra check instead of
"for_each_set_bit(lr, vgic_cpu->lr_used, vgic->nr_lr)", looks stupid to me).

Kind regards,
Pavel Fedin
Expert Engineer
Samsung Electronics Research center Russia