On Wed, Jun 25 2014 at 01:50:12 PM, Rob Herring <robherring2@xxxxxxxxx> wrote: > On Wed, Jun 25, 2014 at 4:28 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote: >> So far, GICv2 has been used in with EOImode == 0. The effect of this >> mode is to perform the priority drop and the deactivation of the >> interrupt at the same time. >> >> While this works perfectly for Linux (we only have a single priority), >> it causes issues when an interrupt is forwarded to a guest, and when >> we want the guest to perform the EOI itself. >> >> For this case, the GIC architecture provides EOImode == 1, where: >> - A write to the EOI register drops the priority of the interrupt and leaves >> it active. Other interrupts at the same priority level can now be taken, >> but the active interrupt cannot be taken again >> - A write to the DIR marks the interrupt as inactive, meaning it can >> now be taken again. >> >> We only enable this feature when booted in HYP mode. Also, as most device >> trees are broken (they report the CPU interface size to be 4kB, while >> the GICv2 CPU interface size is 8kB), output a warning if we're booted >> in HYP mode, and disable the feature. > > Why not fix-up the size so the feature can be enabled? Is it a bet we're willing to take? We'd end-up with a kernel that doesn't boot if the DT was actually right. If we stay with EOImode==0, we can still boot (KVM will probably be broken though). M. -- Jazz is not dead. It just smells funny. _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
