linux-kernel - Re: [PATCH v2 03/18] arm64: KVM: define SPE data structure for each vcpu

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Date:   Tue, 24 Dec 2019 12:01:40 +0000
From:   Andrew Murray <andrew.murray@....com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     will@...nel.org, Catalin Marinas <catalin.marinas@....com>,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Sudeep Holla <sudeep.holla@....com>,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 03/18] arm64: KVM: define SPE data structure for each
 vcpu

On Sat, Dec 21, 2019 at 01:19:36PM +0000, Marc Zyngier wrote:
> On Fri, 20 Dec 2019 14:30:10 +0000
> Andrew Murray <andrew.murray@....com> wrote:
> 
> > From: Sudeep Holla <sudeep.holla@....com>
> > 
> > In order to support virtual SPE for guest, so define some basic structs.
> > This features depends on host having hardware with SPE support.
> > 
> > Since we can support this only on ARM64, add a separate config symbol
> > for the same.
> > 
> > Signed-off-by: Sudeep Holla <sudeep.holla@....com>
> > [ Add irq_level, rename irq to irq_num for kvm_spe ]
> > Signed-off-by: Andrew Murray <andrew.murray@....com>
> > ---
> >  arch/arm64/include/asm/kvm_host.h |  2 ++
> >  arch/arm64/kvm/Kconfig            |  7 +++++++
> >  include/kvm/arm_spe.h             | 19 +++++++++++++++++++
> >  3 files changed, 28 insertions(+)
> >  create mode 100644 include/kvm/arm_spe.h
> > 
> > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> > index c61260cf63c5..f5dcff912645 100644
> > --- a/arch/arm64/include/asm/kvm_host.h
> > +++ b/arch/arm64/include/asm/kvm_host.h
> > @@ -35,6 +35,7 @@
> >  #include <kvm/arm_vgic.h>
> >  #include <kvm/arm_arch_timer.h>
> >  #include <kvm/arm_pmu.h>
> > +#include <kvm/arm_spe.h>
> >  
> >  #define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS
> >  
> > @@ -302,6 +303,7 @@ struct kvm_vcpu_arch {
> >  	struct vgic_cpu vgic_cpu;
> >  	struct arch_timer_cpu timer_cpu;
> >  	struct kvm_pmu pmu;
> > +	struct kvm_spe spe;
> >  
> >  	/*
> >  	 * Anything that is not used directly from assembly code goes
> > diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
> > index a475c68cbfec..af5be2c57dcb 100644
> > --- a/arch/arm64/kvm/Kconfig
> > +++ b/arch/arm64/kvm/Kconfig
> > @@ -35,6 +35,7 @@ config KVM
> >  	select HAVE_KVM_EVENTFD
> >  	select HAVE_KVM_IRQFD
> >  	select KVM_ARM_PMU if HW_PERF_EVENTS
> > +	select KVM_ARM_SPE if (HW_PERF_EVENTS && ARM_SPE_PMU)
> >  	select HAVE_KVM_MSI
> >  	select HAVE_KVM_IRQCHIP
> >  	select HAVE_KVM_IRQ_ROUTING
> > @@ -61,6 +62,12 @@ config KVM_ARM_PMU
> >  	  Adds support for a virtual Performance Monitoring Unit (PMU) in
> >  	  virtual machines.
> >  
> > +config KVM_ARM_SPE
> > +	bool
> > +	---help---
> > +	  Adds support for a virtual Statistical Profiling Extension(SPE) in
> > +	  virtual machines.
> > +
> >  config KVM_INDIRECT_VECTORS
> >         def_bool KVM && (HARDEN_BRANCH_PREDICTOR || HARDEN_EL2_VECTORS)
> >  
> > diff --git a/include/kvm/arm_spe.h b/include/kvm/arm_spe.h
> > new file mode 100644
> > index 000000000000..48d118fdb174
> > --- /dev/null
> > +++ b/include/kvm/arm_spe.h
> > @@ -0,0 +1,19 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/*
> > + * Copyright (C) 2019 ARM Ltd.
> > + */
> > +
> > +#ifndef __ASM_ARM_KVM_SPE_H
> > +#define __ASM_ARM_KVM_SPE_H
> > +
> > +#include <uapi/linux/kvm.h>
> > +#include <linux/kvm_host.h>
> 
> I don't believe these are required at this stage.
> 
> > +
> > +struct kvm_spe {
> > +	int irq_num;
> 
> 'irq' was the right name *if* this represents a Linux irq. If this
> instead represents a guest PPI, then it should be named 'intid'.
> 
> In either case, please document what this represents.
> 
> > +	bool ready; /* indicates that SPE KVM instance is ready for use */
> > +	bool created; /* SPE KVM instance is created, may not be ready yet */
> > +	bool irq_level;
> 
> What does this represent? The state of the interrupt on the host? The
> guest? Something else? Also, please consider grouping related fields
> together.

It should be the state of the interrupt on the guest.

> 
> > +};
> 
> If you've added a config option that controls the selection of the SPE
> feature, why doesn't this result in an empty structure when it isn't
> selected?

OK, all noted.

Andrew Murray

> 
> > +
> > +#endif /* __ASM_ARM_KVM_SPE_H */
> 
> Thanks,
> 
> 	M.
> -- 
> Jazz is not dead. It just smells funny...