Re: [PATCH v11 3/7] KVM: stats: Support binary stats retrieval for a VM

From: Greg KH <gregkh@linuxfoundation.org>
To: Jing Zhang <jingzhangos@google.com>
Cc: KVM <kvm@vger.kernel.org>, KVMARM <kvmarm@lists.cs.columbia.edu>,
	LinuxMIPS <linux-mips@vger.kernel.org>,
	KVMPPC <kvm-ppc@vger.kernel.org>,
	LinuxS390 <linux-s390@vger.kernel.org>,
	Linuxkselftest <linux-kselftest@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Marc Zyngier <maz@kernel.org>, James Morse <james.morse@arm.com>,
	Julien Thierry <julien.thierry.kdev@gmail.com>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Will Deacon <will@kernel.org>,
	Huacai Chen <chenhuacai@kernel.org>,
	Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Paul Mackerras <paulus@ozlabs.org>,
	Christian Borntraeger <borntraeger@de.ibm.com>,
	Janosch Frank <frankja@linux.ibm.com>,
	David Hildenbrand <david@redhat.com>,
	Cornelia Huck <cohuck@redhat.com>,
	Claudio Imbrenda <imbrenda@linux.ibm.com>,
	Sean Christopherson <seanjc@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Jim Mattson <jmattson@google.com>,
	Peter Shier <pshier@google.com>, Oliver Upton <oupton@google.com>,
	David Rientjes <rientjes@google.com>,
	Emanuele Giuseppe Esposito <eesposit@redhat.com>,
	David Matlack <dmatlack@google.com>,
	Ricardo Koller <ricarkol@google.com>,
	Krish Sadhukhan <krish.sadhukhan@oracle.com>,
	Fuad Tabba <tabba@google.com>
Subject: Re: [PATCH v11 3/7] KVM: stats: Support binary stats retrieval for a VM
Date: Fri, 18 Jun 2021 06:58:04 +0000	[thread overview]
Message-ID: <YMxD/NxAvKkXB2iM@kroah.com> (raw)
In-Reply-To: <20210618044819.3690166-4-jingzhangos@google.com>

On Fri, Jun 18, 2021 at 04:48:15AM +0000, Jing Zhang wrote:
> Add a VM ioctl to get a statistics file descriptor by which a read
> functionality is provided for userspace to read out VM stats header,
> descriptors and data.
> Define VM statistics descriptors and header for all architectures.
> 
> Reviewed-by: David Matlack <dmatlack@google.com>
> Reviewed-by: Ricardo Koller <ricarkol@google.com>
> Reviewed-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
> Reviewed-by: Fuad Tabba <tabba@google.com>
> Tested-by: Fuad Tabba <tabba@google.com> #arm64
> Signed-off-by: Jing Zhang <jingzhangos@google.com>
> ---
>  arch/arm64/kvm/guest.c    | 14 +++++++++++++
>  arch/mips/kvm/mips.c      | 14 +++++++++++++
>  arch/powerpc/kvm/book3s.c | 16 +++++++++++++++
>  arch/powerpc/kvm/booke.c  | 16 +++++++++++++++
>  arch/s390/kvm/kvm-s390.c  | 19 +++++++++++++++++
>  arch/x86/kvm/x86.c        | 24 ++++++++++++++++++++++
>  include/linux/kvm_host.h  |  6 ++++++
>  virt/kvm/kvm_main.c       | 43 +++++++++++++++++++++++++++++++++++++++
>  8 files changed, 152 insertions(+)
> 
> diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
> index 4962331d01e6..f456d1defe2b 100644
> --- a/arch/arm64/kvm/guest.c
> +++ b/arch/arm64/kvm/guest.c
> @@ -28,6 +28,20 @@
>  
>  #include "trace.h"
>  
> +struct _kvm_stats_desc kvm_vm_stats_desc[] = {
> +	KVM_GENERIC_VM_STATS()
> +};
> +static_assert(ARRAY_SIZE(kvm_vm_stats_desc) =
> +		sizeof(struct kvm_vm_stat) / sizeof(u64));
> +
> +struct kvm_stats_header kvm_vm_stats_header = {

Can this be const?

> +	.name_size = KVM_STATS_NAME_LEN,
> +	.count = ARRAY_SIZE(kvm_vm_stats_desc),
> +	.desc_offset = sizeof(struct kvm_stats_header) + KVM_STATS_ID_MAXLEN,
> +	.data_offset = sizeof(struct kvm_stats_header) + KVM_STATS_ID_MAXLEN +
> +		       sizeof(kvm_vm_stats_desc),
> +};

If it can't be const, what is modified in it that prevents that from
happening?

thanks,

greg k-h