[PATCH v2 01/15] KVM: arm/arm64: VGIC: don't track used LRs in the distributor

Andre Przywara andre.przywara at arm.com
Fri Oct 2 05:49:17 PDT 2015

Hi Pavel,

On 02/10/15 13:39, Pavel Fedin wrote:
>  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).

I know, because I have reworked my patch lately to work on top of 4.3-rc
and Christoffer's timer rework series. I have something which "works
now"(TM), but wanted to wait for Christoffer's respin to send out.
I will send you this new version this as a sneak preview in private,
maybe that helps.


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