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Re: [Qemu-devel] [PATCH 2/2] arm: kvm: set MPIDR when we can


From: Andrew Jones
Subject: Re: [Qemu-devel] [PATCH 2/2] arm: kvm: set MPIDR when we can
Date: Thu, 2 Mar 2017 17:23:33 +0100
User-agent: Mutt/1.6.0.1 (2016-04-01)

On Thu, Mar 02, 2017 at 04:13:40PM +0000, Peter Maydell wrote:
> On 27 February 2017 at 17:37, Andrew Jones <address@hidden> wrote:
> > If KVM supports user provided MPIDRs for the vcpus, then provide
> > them. This simplifies management of vcpus as we can be sure of
> > the identity of a vcpu even before it's been instantiated.
> >
> > Cc: Igor Mammedov <address@hidden>
> > Signed-off-by: Andrew Jones <address@hidden>
> > ---
> >  target/arm/cpu.c   |  3 +--
> >  target/arm/kvm32.c | 22 ++++++++++++++--------
> >  target/arm/kvm64.c | 22 ++++++++++++++--------
> >  3 files changed, 29 insertions(+), 18 deletions(-)
> >
> > diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> > index f7157dc0e59d..83cd5eefbef8 100644
> > --- a/target/arm/cpu.c
> > +++ b/target/arm/cpu.c
> > @@ -741,8 +741,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error 
> > **errp)
> >          return;
> >      }
> >
> > -    /* This cpu-id-to-MPIDR affinity is used only for TCG; KVM will 
> > override it.
> > -     * We don't support setting cluster ID ([16..23]) (known as Aff2
> > +    /* We don't currently support setting cluster ID ([16..23]) (known as 
> > Aff2
> >       * in later ARM ARM versions), or any of the higher affinity level 
> > fields,
> >       * so these bits always RAZ.
> >       */
> > diff --git a/target/arm/kvm32.c b/target/arm/kvm32.c
> > index 069da0c5fd10..5ad732498e5c 100644
> > --- a/target/arm/kvm32.c
> > +++ b/target/arm/kvm32.c
> > @@ -186,7 +186,6 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >  {
> >      int ret;
> >      uint64_t v;
> > -    uint32_t mpidr;
> >      struct kvm_one_reg r;
> >      ARMCPU *cpu = ARM_CPU(cs);
> >
> > @@ -223,16 +222,23 @@ int kvm_arch_init_vcpu(CPUState *cs)
> >          return -EINVAL;
> >      }
> >
> > -    /*
> > -     * When KVM is in use, PSCI is emulated in-kernel and not by qemu.
> > -     * Currently KVM has its own idea about MPIDR assignment, so we
> > -     * override our defaults with what we get from KVM.
> > -     */
> > -    ret = kvm_get_one_reg(cs, ARM_CP15_REG32(ARM_CPU_ID_MPIDR), &mpidr);
> > +    if (kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_USER_MPIDR)) {
> > +        ret = kvm_set_one_reg(cs, ARM_CP15_REG32(ARM_CPU_ID_MPIDR),
> > +                              &cpu->mp_affinity);
> 
> mp_affinity is only the affinity bits of the MPIDR. I would expect
> the kernel set_one_reg interface for the MPIDR to want a complete
> MPIDR value with M, U and MT bits.

Thanks, I'll fix this.

> 
> (compare the way that when we set mp_affinity from the kernel
> reg. value we mask out the bits we don't care about).
> 
> Similarly with the 64-bit version of this code.
> 
> > +    } else {
> > +        /* If we can't set the MPIDR, then KVM will generate one. We must
> > +         * update our copy to that one in order to stay synchronized.
> > +         */
> > +        uint32_t mpidr;
> > +
> > +        ret = kvm_get_one_reg(cs, ARM_CP15_REG32(ARM_CPU_ID_MPIDR), 
> > &mpidr);
> > +        if (!ret) {
> > +            cpu->mp_affinity = mpidr & ARM32_AFFINITY_MASK;
> > +        }
> > +    }
> >      if (ret) {
> >          return ret;
> >      }
> > -    cpu->mp_affinity = mpidr & ARM32_AFFINITY_MASK;
> >
> >      return kvm_arm_init_cpreg_list(cpu);
> 
> Otherwise this looks fine to me.
> 
> PS: I assume we are targeting 2.10 (or whatever we call it) with this.

Yeah, this is 2.10 material.

Thanks,
drew



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