Re: [PATCH v2 1/1] irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection

From: Lorenzo Pieralisi
Date: Mon Mar 15 2021 - 07:03:17 EST

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In reply to: Marc Zyngier: "Re: [PATCH v2 1/1] irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection"
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On Mon, Mar 08, 2021 at 07:22:57PM +0000, Marc Zyngier wrote:
> Hi Lorenzo,
>
> On Tue, 02 Mar 2021 10:27:44 +0000,
> Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> wrote:
> >
> > GIC CPU interfaces versions predating GIC v4.1 were not built to
> > accommodate vINTID within the vSGI range; as reported in the GIC
> > specifications (8.2 "Changes to the CPU interface"), it is
> > CONSTRAINED UNPREDICTABLE to deliver a vSGI to a PE with
> > ID_AA64PFR0_EL1.GIC < b0011.
> >
> > Check the GIC CPUIF version by reading the SYS_ID_AA64_PFR0_EL1.
> >
> > Disable vSGIs if a CPUIF version < 4.1 is detected to prevent using
> > vSGIs on systems where they may misbehave.
> >
> > Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx>
> > Cc: Marc Zyngier <maz@xxxxxxxxxx>
> > ---
> > arch/arm64/kvm/vgic/vgic-mmio-v3.c | 4 ++--
> > arch/arm64/kvm/vgic/vgic-v3.c | 3 ++-
> > drivers/irqchip/irq-gic-v3-its.c | 6 +++++-
> > drivers/irqchip/irq-gic-v3.c | 22 ++++++++++++++++++++++
> > include/kvm/arm_vgic.h | 1 +
> > include/linux/irqchip/arm-gic-common.h | 2 ++
> > include/linux/irqchip/arm-gic-v3.h | 1 +
> > 7 files changed, 35 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > index 15a6c98ee92f..66548cd2a715 100644
> > --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> > @@ -86,7 +86,7 @@ static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu,
> > }
> > break;
> > case GICD_TYPER2:
> > - if (kvm_vgic_global_state.has_gicv4_1)
> > + if (kvm_vgic_global_state.has_gicv4_1_vsgi)
> > value = GICD_TYPER2_nASSGIcap;
> > break;
> > case GICD_IIDR:
> > @@ -119,7 +119,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
> > dist->enabled = val & GICD_CTLR_ENABLE_SS_G1;
> >
> > /* Not a GICv4.1? No HW SGIs */
> > - if (!kvm_vgic_global_state.has_gicv4_1)
> > + if (!kvm_vgic_global_state.has_gicv4_1_vsgi)
> > val &= ~GICD_CTLR_nASSGIreq;
> >
> > /* Dist stays enabled? nASSGIreq is RO */
> > diff --git a/arch/arm64/kvm/vgic/vgic-v3.c b/arch/arm64/kvm/vgic/vgic-v3.c
> > index 52915b342351..57b73100e8cc 100644
> > --- a/arch/arm64/kvm/vgic/vgic-v3.c
> > +++ b/arch/arm64/kvm/vgic/vgic-v3.c
> > @@ -533,7 +533,7 @@ int vgic_v3_map_resources(struct kvm *kvm)
> > return ret;
> > }
> >
> > - if (kvm_vgic_global_state.has_gicv4_1)
> > + if (kvm_vgic_global_state.has_gicv4_1_vsgi)
> > vgic_v4_configure_vsgis(kvm);
> >
> > return 0;
> > @@ -589,6 +589,7 @@ int vgic_v3_probe(const struct gic_kvm_info *info)
> > if (info->has_v4) {
> > kvm_vgic_global_state.has_gicv4 = gicv4_enable;
> > kvm_vgic_global_state.has_gicv4_1 = info->has_v4_1 && gicv4_enable;
> > + kvm_vgic_global_state.has_gicv4_1_vsgi = info->has_v4_1_vsgi && gicv4_enable;
> > kvm_info("GICv4%s support %sabled\n",
> > kvm_vgic_global_state.has_gicv4_1 ? ".1" : "",
> > gicv4_enable ? "en" : "dis");
> > diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
> > index ed46e6057e33..ee2a2ca27d5c 100644
> > --- a/drivers/irqchip/irq-gic-v3-its.c
> > +++ b/drivers/irqchip/irq-gic-v3-its.c
> > @@ -5412,7 +5412,11 @@ int __init its_init(struct fwnode_handle *handle, struct rdists *rdists,
> > if (has_v4 & rdists->has_vlpis) {
> > const struct irq_domain_ops *sgi_ops;
> >
> > - if (has_v4_1)
> > + /*
> > + * Enable vSGIs only if the ITS and the
> > + * GIC CPUIF support them.
> > + */
> > + if (has_v4_1 && rdists->has_vsgi_cpuif)
> > sgi_ops = &its_sgi_domain_ops;
> > else
> > sgi_ops = NULL;
>
> This doesn't seem right. If you pass NULL for the SGI ops, you also
> lose the per-VPE doorbells and stick to the terrible GICv4.0 behaviour
> (see the use of has_v4_1() in irq-gic-v4.c). I don't think that is
> what you really want.

Yes, I was caught out again - we use the sgi_ops to detect v4.1 behaviour,
I will remove this hunk.

> > diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c
> > index eb0ee356a629..fd6cd9a5de34 100644
> > --- a/drivers/irqchip/irq-gic-v3.c
> > +++ b/drivers/irqchip/irq-gic-v3.c
> > @@ -31,6 +31,21 @@
> >
> > #include "irq-gic-common.h"
> >
> > +#ifdef CONFIG_ARM64
> > +#include <asm/cpufeature.h>
> > +
> > +static inline bool gic_cpuif_has_vsgi(void)
> > +{
> > + unsigned long fld, reg = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
> > +
> > + fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64PFR0_GIC_SHIFT);
> > +
> > + return fld >= 0x3;
> > +}
> > +#else
> > +static inline bool gic_cpuif_has_vsgi(void) { return false; }
> > +#endif
>
> Why do we need to expose this in the GICv3 driver instead of the GICv4
> code? At the moment, you track this state:
>
> - in gic_data.rdists.has_vsgi_cpuif
> - indirectly in gic_v3_kvm_info.has_v4_1_vsgi
> - indirectly in kvm_vgic_global_state.has_gicv4_1_vsgi
>
> Can't we simplify the logic and track it *once*? Or even better, just
> evaluate it when required? I hacked the following stuff based on your
> patch (untested). What do you think?

Thanks for that I will give it a shot - it makes sense. I will have
a look to see if we can consolidate these v4.0 vs v4.1 checks somehow
before reposting.

Thanks a lot for the review.

Lorenzo

> Thanks,
>
> M.
>
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> index 15a6c98ee92f..2f1b156021a6 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c
> @@ -86,7 +86,7 @@ static unsigned long vgic_mmio_read_v3_misc(struct kvm_vcpu *vcpu,
> }
> break;
> case GICD_TYPER2:
> - if (kvm_vgic_global_state.has_gicv4_1)
> + if (kvm_vgic_global_state.has_gicv4_1 && gic_cpuif_has_vsgi())
> value = GICD_TYPER2_nASSGIcap;
> break;
> case GICD_IIDR:
> @@ -119,7 +119,7 @@ static void vgic_mmio_write_v3_misc(struct kvm_vcpu *vcpu,
> dist->enabled = val & GICD_CTLR_ENABLE_SS_G1;
>
> /* Not a GICv4.1? No HW SGIs */
> - if (!kvm_vgic_global_state.has_gicv4_1)
> + if (!kvm_vgic_global_state.has_gicv4_1 || !gic_cpuif_has_vsgi())
> val &= ~GICD_CTLR_nASSGIreq;
>
> /* Dist stays enabled? nASSGIreq is RO */
> diff --git a/drivers/irqchip/irq-gic-v4.c b/drivers/irqchip/irq-gic-v4.c
> index 5d1dc9915272..864fa9bbda4c 100644
> --- a/drivers/irqchip/irq-gic-v4.c
> +++ b/drivers/irqchip/irq-gic-v4.c
> @@ -87,17 +87,37 @@ static struct irq_domain *gic_domain;
> static const struct irq_domain_ops *vpe_domain_ops;
> static const struct irq_domain_ops *sgi_domain_ops;
>
> +#ifdef CONFIG_ARM64
> +#include <asm/cpufeature.h>
> +
> +bool gic_cpuif_has_vsgi(void)
> +{
> + unsigned long fld, reg = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
> +
> + fld = cpuid_feature_extract_unsigned_field(reg, ID_AA64PFR0_GIC_SHIFT);
> +
> + return fld >= 0x3;
> +}
> +#else
> +bool gic_cpuif_has_vsgi(void) { }
> +#endif
> +
> static bool has_v4_1(void)
> {
> return !!sgi_domain_ops;
> }
>
> +static bool has_v4_1_sgi(void)
> +{
> + return has_v4_1() && gic_cpuif_has_vsgi();
> +}
> +
> static int its_alloc_vcpu_sgis(struct its_vpe *vpe, int idx)
> {
> char *name;
> int sgi_base;
>
> - if (!has_v4_1())
> + if (!has_v4_1_sgi())
> return 0;
>
> name = kasprintf(GFP_KERNEL, "GICv4-sgi-%d", task_pid_nr(current));
> @@ -182,7 +202,7 @@ static void its_free_sgi_irqs(struct its_vm *vm)
> {
> int i;
>
> - if (!has_v4_1())
> + if (!has_v4_1_sgi())
> return;
>
> for (i = 0; i < vm->nr_vpes; i++) {
> diff --git a/include/linux/irqchip/arm-gic-v4.h b/include/linux/irqchip/arm-gic-v4.h
> index 943c3411ca10..2c63375bbd43 100644
> --- a/include/linux/irqchip/arm-gic-v4.h
> +++ b/include/linux/irqchip/arm-gic-v4.h
> @@ -145,4 +145,6 @@ int its_init_v4(struct irq_domain *domain,
> const struct irq_domain_ops *vpe_ops,
> const struct irq_domain_ops *sgi_ops);
>
> +bool gic_cpuif_has_vsgi(void);
> +
> #endif
>
> --
> Without deviation from the norm, progress is not possible.

Next message: Geert Uytterhoeven: "Re: Build regressions/improvements in v5.12-rc3"
Previous message: Stefano Garzarella: "Re: [RFC PATCH v6 11/22] virtio/vsock: dequeue callback for SOCK_SEQPACKET"
In reply to: Marc Zyngier: "Re: [PATCH v2 1/1] irqchip/gic-v4.1: Disable vSGI upon (GIC CPUIF < v4.1) detection"
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