From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoffer Dall Subject: Re: [PATCH v3 56/59] KVM: arm/arm64: GICv4: Prevent heterogenous systems from using GICv4 Date: Wed, 30 Aug 2017 23:00:27 +0200 Message-ID: <20170830210027.GO24522@cbox> References: <20170731172637.29355-1-marc.zyngier@arm.com> <20170731172637.29355-57-marc.zyngier@arm.com> <20170828183550.GQ24649@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Jason Cooper , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner , kvmarm@lists.cs.columbia.edu To: Marc Zyngier Return-path: Content-Disposition: inline In-Reply-To: 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 On Wed, Aug 30, 2017 at 05:03:51PM +0100, Marc Zyngier wrote: > On 28/08/17 19:35, Christoffer Dall wrote: > > On Mon, Jul 31, 2017 at 06:26:34PM +0100, Marc Zyngier wrote: > >> The GICv4 architecture doesn't prevent CPUs implementing GICv4 to > >> cohabit with CPUs limited to GICv3 in the same system. > >> > >> This is mad (the sheduler would have to be made aware of the v4 > > > > *scheduler > > > >> capability), and we're certainly not going to support this any > >> time soon. So let's check that all online CPUs are GICv4 capable, > >> and disable the functionnality if not. > > > > *functionality > > > >> > >> Signed-off-by: Marc Zyngier > >> --- > >> include/linux/irqchip/arm-gic-v3.h | 2 ++ > >> virt/kvm/arm/vgic/vgic-v3.c | 22 +++++++++++++++++++++- > >> 2 files changed, 23 insertions(+), 1 deletion(-) > >> > >> diff --git a/include/linux/irqchip/arm-gic-v3.h b/include/linux/irqchip/arm-gic-v3.h > >> index 1ea576c8126f..dfa4a51643d6 100644 > >> --- a/include/linux/irqchip/arm-gic-v3.h > >> +++ b/include/linux/irqchip/arm-gic-v3.h > >> @@ -532,6 +532,8 @@ > >> #define ICH_VTR_SEIS_MASK (1 << ICH_VTR_SEIS_SHIFT) > >> #define ICH_VTR_A3V_SHIFT 21 > >> #define ICH_VTR_A3V_MASK (1 << ICH_VTR_A3V_SHIFT) > >> +#define ICH_VTR_nV4_SHIFT 20 > >> +#define ICH_VTR_nV4_MASK (1 << ICH_VTR_nV4_SHIFT) > >> > >> #define ICC_IAR1_EL1_SPURIOUS 0x3ff > >> > >> diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c > >> index 405733678c2f..252268e83ade 100644 > >> --- a/virt/kvm/arm/vgic/vgic-v3.c > >> +++ b/virt/kvm/arm/vgic/vgic-v3.c > >> @@ -466,6 +466,18 @@ static int __init early_gicv4_enable(char *buf) > >> } > >> early_param("kvm-arm.vgic_v4_enable", early_gicv4_enable); > >> > >> +static void vgic_check_v4_cpuif(void *param) > >> +{ > >> + u32 ich_vtr_el2 = kvm_call_hyp(__vgic_v3_get_ich_vtr_el2); > >> + bool *v4 = param, this_cpu_is_v4; > >> + > >> + this_cpu_is_v4 = !(ich_vtr_el2 & ICH_VTR_nV4_MASK); > >> + if (!this_cpu_is_v4) > >> + kvm_info("CPU%d is not GICv4 capable\n", smp_processor_id()); > >> + > >> + *v4 &= this_cpu_is_v4; > > > > nit: You could make this function look slightly less scary by declaring > > this_cpu_is_v4 on a separate line and not use a bitwise operator on a > > boolean type. Actually, having a function called 'check' with a side > > effect is not the nicest thing either, so why not just return what this > > particular CPU does and do the comparison in the calling loop. > > Fair enough. > > > #bikeshedding > > How about this on top: > > diff --git a/virt/kvm/arm/vgic/vgic-v3.c b/virt/kvm/arm/vgic/vgic-v3.c > index 01eaf4ee2f63..e471750dc0a1 100644 > --- a/virt/kvm/arm/vgic/vgic-v3.c > +++ b/virt/kvm/arm/vgic/vgic-v3.c > @@ -469,18 +469,16 @@ early_param("kvm-arm.vgic_v4_enable", early_gicv4_enable); > static void vgic_check_v4_cpuif(void *param) > { > u32 ich_vtr_el2 = kvm_call_hyp(__vgic_v3_get_ich_vtr_el2); > - bool *v4 = param, this_cpu_is_v4; > + bool *v4 = param; > > - this_cpu_is_v4 = !(ich_vtr_el2 & ICH_VTR_nV4_MASK); > - if (!this_cpu_is_v4) > + *v4 = !(ich_vtr_el2 & ICH_VTR_nV4_MASK); > + if (!*v4) > kvm_info("CPU%d is not GICv4 capable\n", smp_processor_id()); > - > - *v4 &= this_cpu_is_v4; > } > > /** > * vgic_v3_probe - probe for a GICv3 compatible interrupt controller in DT > - * @node: pointer to the DT node > + * @info: pointer to the firmware-agnostic GIC information > * > * Returns 0 if a GICv3 has been found, returns an error code otherwise > */ > @@ -504,9 +502,14 @@ int vgic_v3_probe(const struct gic_kvm_info *info) > if (info->has_v4) { > int cpu; > > - for_each_online_cpu(cpu) > + for_each_online_cpu(cpu) { > + bool enable; > + > smp_call_function_single(cpu, vgic_check_v4_cpuif, > - &gicv4_enable, 1); > + &enable, 1); > + gicv4_enable = gicv4_enable && enable; > + } > + > kvm_vgic_global_state.has_gicv4 = gicv4_enable; > kvm_info("GICv4 support %sabled\n", > gicv4_enable ? "en" : "dis"); > Looks good to me, thanks! -Christoffer