On Wed, Oct 18, 2017 at 05:03:40PM +0100, Marc Zyngier wrote: > On Wed, Oct 18 2017 at 3:41:45 pm BST, Christoffer Dall <cdall@xxxxxxxxxx> wrote: > > On Mon, Oct 09, 2017 at 05:47:18PM +0100, Marc Zyngier wrote: > >> On 23/09/17 01:41, Christoffer Dall wrote: > >> > Some systems without proper firmware and/or hardware description data > >> > don't support the split EOI and deactivate operation. > >> > > >> > On such systems, we cannot leave the physical interrupt active after the > >> > timer handler on the host has run, so we cannot support KVM with an > >> > in-kernel GIC with the timer changes we are about to introduce. > >> > > >> > This patch makes sure that trying to initialize the KVM GIC code will > >> > fail on such systems. > >> > > >> > Cc: Marc Zyngier <marc.zyngier@xxxxxxx> > >> > Signed-off-by: Christoffer Dall <cdall@xxxxxxxxxx> > >> > --- > >> > drivers/irqchip/irq-gic.c | 3 ++- > >> > 1 file changed, 2 insertions(+), 1 deletion(-) > >> > > >> > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c > >> > index f641e8e..ab12bf4 100644 > >> > --- a/drivers/irqchip/irq-gic.c > >> > +++ b/drivers/irqchip/irq-gic.c > >> > @@ -1420,7 +1420,8 @@ static void __init gic_of_setup_kvm_info(struct device_node *node) > >> > if (ret) > >> > return; > >> > > >> > - gic_set_kvm_info(&gic_v2_kvm_info); > >> > + if (static_key_true(&supports_deactivate)) > >> > + gic_set_kvm_info(&gic_v2_kvm_info); > >> > } > >> > > >> > int __init > >> > > >> > >> Should we add the same level of checking on the ACPI path, just for the > >> sake symmetry? > > > > Yes, we should, if anyone is crazy enough to use ACPI :) > > Sadly, the madness is becoming commonplace. > > >> > >> Also, do we need to add the same thing for GICv3? > >> > > > > Why would split EOI/deactivate not be available on GICv3, actually? It > > looks like this is not supported unless you have EL2, but I can't seem > > to find anything in the spec for this, and KVM should support > > EOI/deactivate for GICv3 guests I think. Am I missing something? > > No, you're not. This is just a Linux choice (or rather mine) not to use > EOImode=1 in guests (or anything booted at EL1), as we don't really need > the two-stage deactivate in that situation (it is pure overhead). > > I'm just worried of potentially broken HW, and would like to make sure > that when we force EOImode=0 on these systems, we truly tell KVM about > it. > Yes, makes sense, it's also more cosistent that way. > > Assuming I'm wrong about GICv3, which I probably am, how does this look > > (on top of the posted patch): > > > > diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c > > index 519149e..aed524c 100644 > > --- a/drivers/irqchip/irq-gic-v3.c > > +++ b/drivers/irqchip/irq-gic-v3.c > > @@ -1228,7 +1228,9 @@ static int __init gic_of_init(struct device_node *node, struct device_node *pare > > goto out_unmap_rdist; > > > > gic_populate_ppi_partitions(node); > > - gic_of_setup_kvm_info(node); > > + > > + if (static_key_true(&supports_deactivate)) > > + gic_of_setup_kvm_info(node); > > return 0; > > > > out_unmap_rdist: > > @@ -1517,7 +1519,9 @@ gic_acpi_init(struct acpi_subtable_header *header, const unsigned long end) > > goto out_fwhandle_free; > > > > acpi_set_irq_model(ACPI_IRQ_MODEL_GIC, domain_handle); > > - gic_acpi_setup_kvm_info(); > > + > > + if (static_key_true(&supports_deactivate)) > > + gic_acpi_setup_kvm_info(); > > > > return 0; > > > > diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c > > index ab12bf4..121af5c 100644 > > --- a/drivers/irqchip/irq-gic.c > > +++ b/drivers/irqchip/irq-gic.c > > @@ -1653,7 +1653,8 @@ static int __init gic_v2_acpi_init(struct acpi_subtable_header *header, > > if (IS_ENABLED(CONFIG_ARM_GIC_V2M)) > > gicv2m_init(NULL, gic_data[0].domain); > > > > - gic_acpi_setup_kvm_info(); > > + if (static_key_true(&supports_deactivate)) > > + gic_acpi_setup_kvm_info(); > > > > return 0; > > } > > Yup, looks good to me! > Thanks, -Christoffer
