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Re: [PATCH v3 11/16] KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_

To: Christoffer Dall <cdall@kernel.org>
Subject: Re: [PATCH v3 11/16] KVM: Move vcpu_load to arch-specific kvm_arch_vcpu_ioctl_set_guest_debug
From: Cornelia Huck <cohuck@redhat.com>
Date: Mon, 11 Dec 2017 13:39:43 +0100
Cc: kvm@vger.kernel.org, Andrew Jones <drjones@redhat.com>, Christoffer Dall <christoffer.dall@linaro.org>, Paolo Bonzini <pbonzini@redhat.com>, Radim Krčmář <rkrcmar@redhat.com>, Marc Zyngier <marc.zyngier@arm.com>, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, James Hogan <jhogan@kernel.org>, linux-mips@linux-mips.org, Paul Mackerras <paulus@ozlabs.org>, kvm-ppc@vger.kernel.org, Christian Borntraeger <borntraeger@de.ibm.com>, linux-s390@vger.kernel.org
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On Mon,  4 Dec 2017 21:35:33 +0100
Christoffer Dall <cdall@kernel.org> wrote:

> From: Christoffer Dall <christoffer.dall@linaro.org>
> 
> Move vcpu_load() and vcpu_put() into the architecture specific
> implementations of kvm_arch_vcpu_ioctl_set_guest_debug().
> 
> Reviewed-by: David Hildenbrand <david@redhat.com>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
>  arch/arm64/kvm/guest.c    | 15 ++++++++++++---
>  arch/powerpc/kvm/book3s.c |  2 ++
>  arch/powerpc/kvm/booke.c  | 19 +++++++++++++------
>  arch/s390/kvm/kvm-s390.c  | 16 ++++++++++++----
>  arch/x86/kvm/x86.c        |  4 +++-
>  virt/kvm/kvm_main.c       |  2 --
>  6 files changed, 42 insertions(+), 16 deletions(-)
> 

> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index 1b491b89cd43..7cb0e2677e60 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -2018,12 +2018,15 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct 
> kvm_vcpu *vcpu,
>  {
>       struct debug_reg *dbg_reg;
>       int n, b = 0, w = 0;
> +     int ret = 0;
> +
> +     vcpu_load(vcpu);
>  
>       if (!(dbg->control & KVM_GUESTDBG_ENABLE)) {
>               vcpu->arch.dbg_reg.dbcr0 = 0;
>               vcpu->guest_debug = 0;
>               kvm_guest_protect_msr(vcpu, MSR_DE, false);
> -             return 0;
> +             goto out;
>       }
>  
>       kvm_guest_protect_msr(vcpu, MSR_DE, true);
> @@ -2055,8 +2058,9 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu 
> *vcpu,
>  #endif
>  
>       if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))
> -             return 0;
> +             goto out;
>  
> +     ret = -EINVAL;
>       for (n = 0; n < (KVMPPC_BOOKE_IAC_NUM + KVMPPC_BOOKE_DAC_NUM); n++) {
>               uint64_t addr = dbg->arch.bp[n].addr;
>               uint32_t type = dbg->arch.bp[n].type;
> @@ -2067,21 +2071,24 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct 
> kvm_vcpu *vcpu,
>               if (type & ~(KVMPPC_DEBUG_WATCH_READ |
>                            KVMPPC_DEBUG_WATCH_WRITE |
>                            KVMPPC_DEBUG_BREAKPOINT))
> -                     return -EINVAL;
> +                     goto out;
>  
>               if (type & KVMPPC_DEBUG_BREAKPOINT) {
>                       /* Setting H/W breakpoint */
>                       if (kvmppc_booke_add_breakpoint(dbg_reg, addr, b++))
> -                             return -EINVAL;
> +                             goto out;
>               } else {
>                       /* Setting H/W watchpoint */
>                       if (kvmppc_booke_add_watchpoint(dbg_reg, addr,
>                                                       type, w++))
> -                             return -EINVAL;
> +                             goto out;
>               }
>       }
>  
> -     return 0;
> +     ret = 0;

I would probably set the -EINVAL in the individual branches (so it is
clear that something is wrong, and it is not just a benign exit as in
the cases above), but your code is correct as well. Let the powerpc
folks decide.

> +out:
> +     vcpu_put(vcpu);
> +     return ret;
>  }
>  
>  void kvmppc_booke_vcpu_load(struct kvm_vcpu *vcpu, int cpu)

In any case,

Reviewed-by: Cornelia Huck <cohuck@redhat.com>

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