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

[Auger Eric <eric.auger@redhat.com>]

Adding Prakash B in cc too, sorry.

Vijaya, please let me know if I missed something in your original patch.

I tested GICv3 KVM save/restore with v4.11-rc4 and Prakash B use case
with 4.10 kernel.

Thanks

Eric

On 28/03/2017 15:58, Eric Auger 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 <eric.auger@redhat.com>
> Reported-by: Prakash B <bjsprakash.linux@gmail.com>
> 
> ---
> 
> 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;
> +    }
> +    /* 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)
>