Re: [PATCH v3 1/2] KVM: PPC: New capability to control MCE behaviour

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jan 14, 2016 at 11:02:39AM +1100, David Gibson wrote:
> On Wed, Jan 13, 2016 at 12:37:59PM +0530, Aravinda Prasad wrote:
> > This patch introduces a new KVM capability to control
> > how KVM behaves on machine check exception (MCE).
> > Without this capability, KVM redirects machine check
> > exceptions to guest's 0x200 vector if the address in
> > error belongs to the guest. With this capability KVM
> > causes a guest exit with NMI exit reason.
> > 
> > This is required to avoid problems if a new kernel/KVM
> > is used with an old QEMU for guests that don't issue
> > "ibm,nmi-register". As old QEMU does not understand the
> > NMI exit type, it treats it as a fatal error. However,
> > the guest could have handled the machine check error
> > if the exception was delivered to guest's 0x200 interrupt
> > vector instead of NMI exit in case of old QEMU.
> > 
> > QEMU part can be found at:
> > http://lists.nongnu.org/archive/html/qemu-ppc/2015-12/msg00199.html
> > 
> > Change Log v3:
> >   - Split the patch into 2. First patch introduces the
> >     new capability while the second one enhances KVM to
> >     redirect MCE.
> >   - Fix access width bug
> >   - Rebased to v4.4-rc7
> > 
> > Change Log v2:
> >   - Added KVM capability
> > 
> > Signed-off-by: Aravinda Prasad <aravinda@linux.vnet.ibm.com>
> > ---
> >  arch/powerpc/include/asm/kvm_host.h |    1 +
> >  arch/powerpc/kernel/asm-offsets.c   |    1 +
> >  arch/powerpc/kvm/powerpc.c          |    7 +++++++
> >  include/uapi/linux/kvm.h            |    1 +
> >  4 files changed, 10 insertions(+)
> > 
> > diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> > index cfa758c..9ac2b84 100644
> > --- a/arch/powerpc/include/asm/kvm_host.h
> > +++ b/arch/powerpc/include/asm/kvm_host.h
> > @@ -243,6 +243,7 @@ struct kvm_arch {
> >  	int hpt_cma_alloc;
> >  	struct dentry *debugfs_dir;
> >  	struct dentry *htab_dentry;
> > +	u8 fwnmi_enabled;
> 
> Um.. I don't see anything in this patch or 2/2 which actually tests
> this flag...

Sorry, I missed it in the asm, spotted it now.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> 
> >  #endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */
> >  #ifdef CONFIG_KVM_BOOK3S_PR_POSSIBLE
> >  	struct mutex hpt_mutex;
> > diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> > index 221d584..6a4e81a 100644
> > --- a/arch/powerpc/kernel/asm-offsets.c
> > +++ b/arch/powerpc/kernel/asm-offsets.c
> > @@ -506,6 +506,7 @@ int main(void)
> >  	DEFINE(KVM_ENABLED_HCALLS, offsetof(struct kvm, arch.enabled_hcalls));
> >  	DEFINE(KVM_LPCR, offsetof(struct kvm, arch.lpcr));
> >  	DEFINE(KVM_VRMA_SLB_V, offsetof(struct kvm, arch.vrma_slb_v));
> > +	DEFINE(KVM_FWNMI, offsetof(struct kvm, arch.fwnmi_enabled));
> >  	DEFINE(VCPU_DSISR, offsetof(struct kvm_vcpu, arch.shregs.dsisr));
> >  	DEFINE(VCPU_DAR, offsetof(struct kvm_vcpu, arch.shregs.dar));
> >  	DEFINE(VCPU_VPA, offsetof(struct kvm_vcpu, arch.vpa.pinned_addr));
> > diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
> > index 6fd2405..a8399b5 100644
> > --- a/arch/powerpc/kvm/powerpc.c
> > +++ b/arch/powerpc/kvm/powerpc.c
> > @@ -570,6 +570,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
> >  		r = 1;
> >  		break;
> >  #endif
> > +	case KVM_CAP_PPC_FWNMI:
> > +		r = 1;
> > +		break;
> >  	default:
> >  		r = 0;
> >  		break;
> > @@ -1132,6 +1135,10 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
> >  		break;
> >  	}
> >  #endif /* CONFIG_KVM_XICS */
> > +	case KVM_CAP_PPC_FWNMI:
> > +		r = 0;
> > +		vcpu->kvm->arch.fwnmi_enabled = true;
> > +		break;
> >  	default:
> >  		r = -EINVAL;
> >  		break;
> > diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> > index 03f3618..d8a07b5 100644
> > --- a/include/uapi/linux/kvm.h
> > +++ b/include/uapi/linux/kvm.h
> > @@ -831,6 +831,7 @@ struct kvm_ppc_smmu_info {
> >  #define KVM_CAP_GUEST_DEBUG_HW_WPS 120
> >  #define KVM_CAP_SPLIT_IRQCHIP 121
> >  #define KVM_CAP_IOEVENTFD_ANY_LENGTH 122
> > +#define KVM_CAP_PPC_FWNMI 123
> >  
> >  #ifdef KVM_CAP_IRQ_ROUTING
> >  
> > 
> 



-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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