Re: [Qemu-devel] [PATCH] hw/intc/arm_gicv3_kvm: Check KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS in reset

[Vijay Kilari]

Hi Eric,

On Tue, Mar 28, 2017 at 7:28 PM, Eric Auger <address@hidden> wrote:
> KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS needs to be checked before
> attempting to read ICC_CTLR_EL1; otherwise kernel versions not
> exposing this kvm device group will be incompatible with qemu 2.9.
>
> Fixes: 07a5628  ("hw/intc/arm_gicv3_kvm: Reset GICv3 cpu interface registers")
> Signed-off-by: Eric Auger <address@hidden>
> Reported-by: Prakash B <address@hidden>
>
> ---
>
> I understand the ICC_CTLR_EL1 state only is used in the put() function
> which is used for migration
> ---
>  hw/intc/arm_gicv3_kvm.c | 17 +++++++++++------
>  1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
> index 81f0403..4c3a88e 100644
> --- a/hw/intc/arm_gicv3_kvm.c
> +++ b/hw/intc/arm_gicv3_kvm.c
> @@ -614,12 +614,6 @@ static void arm_gicv3_icc_reset(CPUARMState *env, const 
> ARMCPRegInfo *ri)
>      s = c->gic;
>      cpu = ARM_CPU(c->cpu);
>
> -    /* Initialize to actual HW supported configuration */
> -    kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
> -                      KVM_VGIC_ATTR(ICC_CTLR_EL1, cpu->mp_affinity),
> -                      &c->icc_ctlr_el1[GICV3_NS], false);
> -
> -    c->icc_ctlr_el1[GICV3_S] = c->icc_ctlr_el1[GICV3_NS];
>      c->icc_pmr_el1 = 0;
>      c->icc_bpr[GICV3_G0] = GIC_MIN_BPR;
>      c->icc_bpr[GICV3_G1] = GIC_MIN_BPR;
> @@ -628,6 +622,17 @@ static void arm_gicv3_icc_reset(CPUARMState *env, const 
> ARMCPRegInfo *ri)
>      c->icc_sre_el1 = 0x7;
>      memset(c->icc_apr, 0, sizeof(c->icc_apr));
>      memset(c->icc_igrpen, 0, sizeof(c->icc_igrpen));
> +
> +    if (!kvm_device_check_attr(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
> +                              KVM_VGIC_ATTR(ICC_CTLR_EL1, 
> cpu->mp_affinity))) {
> +        return;
> +    }

 Can't we use gicv3 migration blocker provided if it is set before this reset.

> +    /* Initialize to actual HW supported configuration */
> +    kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
> +                      KVM_VGIC_ATTR(ICC_CTLR_EL1, cpu->mp_affinity),
> +                      &c->icc_ctlr_el1[GICV3_NS], false);
> +
> +    c->icc_ctlr_el1[GICV3_S] = c->icc_ctlr_el1[GICV3_NS];
>  }
>
>  static void kvm_arm_gicv3_reset(DeviceState *dev)
> --
> 2.5.5
>