From: Paolo Bonzini <pbonzini@redhat.com>
To: Greg KH <greg@kroah.com>, Jing Zhang <jingzhangos@google.com>
Cc: KVM <kvm@vger.kernel.org>, David Hildenbrand <david@redhat.com>,
Paul Mackerras <paulus@ozlabs.org>,
Linuxkselftest <linux-kselftest@vger.kernel.org>,
Claudio Imbrenda <imbrenda@linux.ibm.com>,
Will Deacon <will@kernel.org>,
KVMARM <kvmarm@lists.cs.columbia.edu>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>,
LinuxS390 <linux-s390@vger.kernel.org>,
Janosch Frank <frankja@linux.ibm.com>,
Marc Zyngier <maz@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Aleksandar Markovic <aleksandar.qemu.devel@gmail.com>,
David Rientjes <rientjes@google.com>,
KVMPPC <kvm-ppc@vger.kernel.org>,
Krish Sadhukhan <krish.sadhukhan@oracle.com>,
David Matlack <dmatlack@google.com>,
Jim Mattson <jmattson@google.com>,
Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
Sean Christopherson <seanjc@google.com>,
Cornelia Huck <cohuck@redhat.com>,
Peter Shier <pshier@google.com>,
LinuxMIPS <linux-mips@vger.kernel.org>,
Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH v10 2/5] KVM: stats: Add fd-based API to read binary stats data
Date: Thu, 17 Jun 2021 13:23:35 +0200 [thread overview]
Message-ID: <d8ca6601-e3b7-e6b1-5992-12ae106de951@redhat.com> (raw)
In-Reply-To: <YMrzzYEkDQNCpnP7@kroah.com>
On 17/06/21 09:03, Greg KH wrote:
>> 3. Fd-based solution provides the possibility that a telemetry can
>> read KVM stats in a less privileged situation.
> "possiblity"? Does this work or not? Have you tested it?
>
I think this is essentially s/that/for/. But more precisely:
3. Compared for example to a ioctl, a separate file descriptor makes it
possible for an external program to read statistics, while maintaining
privilege separation between VMM and telemetry code.
>>
>> + snprintf(&kvm_vm_stats_header.id[0], sizeof(kvm_vm_stats_header.id),
>> + "kvm-%d", task_pid_nr(current));
>
> Why do you write to this static variable for EVERY read? Shouldn't you
> just do it once at open? How can it change?
>
> Wait, it's a single shared variable, what happens when multiple tasks
> open this thing and read from it? You race between writing to this
> variable here and then:
>
>> + return kvm_stats_read(&kvm_vm_stats_header, &kvm_vm_stats_desc[0],
>> + &kvm->stat, sizeof(kvm->stat), user_buffer, size, offset);
>
> Accessing it here.
>
> So how is this really working?
It's not - Jing, kvm_vm_stats_header is small enough that you can store
a copy in struct kvm.
Paolo
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WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Greg KH <greg@kroah.com>, 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>,
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 v10 2/5] KVM: stats: Add fd-based API to read binary stats data
Date: Thu, 17 Jun 2021 13:23:35 +0200 [thread overview]
Message-ID: <d8ca6601-e3b7-e6b1-5992-12ae106de951@redhat.com> (raw)
In-Reply-To: <YMrzzYEkDQNCpnP7@kroah.com>
On 17/06/21 09:03, Greg KH wrote:
>> 3. Fd-based solution provides the possibility that a telemetry can
>> read KVM stats in a less privileged situation.
> "possiblity"? Does this work or not? Have you tested it?
>
I think this is essentially s/that/for/. But more precisely:
3. Compared for example to a ioctl, a separate file descriptor makes it
possible for an external program to read statistics, while maintaining
privilege separation between VMM and telemetry code.
>>
>> + snprintf(&kvm_vm_stats_header.id[0], sizeof(kvm_vm_stats_header.id),
>> + "kvm-%d", task_pid_nr(current));
>
> Why do you write to this static variable for EVERY read? Shouldn't you
> just do it once at open? How can it change?
>
> Wait, it's a single shared variable, what happens when multiple tasks
> open this thing and read from it? You race between writing to this
> variable here and then:
>
>> + return kvm_stats_read(&kvm_vm_stats_header, &kvm_vm_stats_desc[0],
>> + &kvm->stat, sizeof(kvm->stat), user_buffer, size, offset);
>
> Accessing it here.
>
> So how is this really working?
It's not - Jing, kvm_vm_stats_header is small enough that you can store
a copy in struct kvm.
Paolo
WARNING: multiple messages have this Message-ID (diff)
From: Paolo Bonzini <pbonzini@redhat.com>
To: Greg KH <greg@kroah.com>, 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>,
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 v10 2/5] KVM: stats: Add fd-based API to read binary stats data
Date: Thu, 17 Jun 2021 11:23:35 +0000 [thread overview]
Message-ID: <d8ca6601-e3b7-e6b1-5992-12ae106de951@redhat.com> (raw)
In-Reply-To: <YMrzzYEkDQNCpnP7@kroah.com>
On 17/06/21 09:03, Greg KH wrote:
>> 3. Fd-based solution provides the possibility that a telemetry can
>> read KVM stats in a less privileged situation.
> "possiblity"? Does this work or not? Have you tested it?
>
I think this is essentially s/that/for/. But more precisely:
3. Compared for example to a ioctl, a separate file descriptor makes it
possible for an external program to read statistics, while maintaining
privilege separation between VMM and telemetry code.
>>
>> + snprintf(&kvm_vm_stats_header.id[0], sizeof(kvm_vm_stats_header.id),
>> + "kvm-%d", task_pid_nr(current));
>
> Why do you write to this static variable for EVERY read? Shouldn't you
> just do it once at open? How can it change?
>
> Wait, it's a single shared variable, what happens when multiple tasks
> open this thing and read from it? You race between writing to this
> variable here and then:
>
>> + return kvm_stats_read(&kvm_vm_stats_header, &kvm_vm_stats_desc[0],
>> + &kvm->stat, sizeof(kvm->stat), user_buffer, size, offset);
>
> Accessing it here.
>
> So how is this really working?
It's not - Jing, kvm_vm_stats_header is small enough that you can store
a copy in struct kvm.
Paolo
next prev parent reply other threads:[~2021-06-17 11:40 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-17 4:41 [PATCH v10 0/5] KVM statistics data fd-based binary interface Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` [PATCH v10 1/5] KVM: stats: Separate generic stats from architecture specific ones Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` [PATCH v10 2/5] KVM: stats: Add fd-based API to read binary stats data Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 7:03 ` Greg KH
2021-06-17 7:03 ` Greg KH
2021-06-17 7:03 ` Greg KH
2021-06-17 11:23 ` Paolo Bonzini [this message]
2021-06-17 11:23 ` Paolo Bonzini
2021-06-17 11:23 ` Paolo Bonzini
2021-06-17 14:48 ` Jing Zhang
2021-06-17 14:48 ` Jing Zhang
2021-06-17 14:48 ` Jing Zhang
2021-06-17 7:24 ` Greg KH
2021-06-17 7:24 ` Greg KH
2021-06-17 7:24 ` Greg KH
2021-06-17 11:27 ` Paolo Bonzini
2021-06-17 11:27 ` Paolo Bonzini
2021-06-17 11:27 ` Paolo Bonzini
2021-06-17 14:56 ` Jing Zhang
2021-06-17 14:56 ` Jing Zhang
2021-06-17 14:56 ` Jing Zhang
2021-06-17 15:29 ` Paolo Bonzini
2021-06-17 15:29 ` Paolo Bonzini
2021-06-17 15:29 ` Paolo Bonzini
2021-06-17 15:42 ` Jing Zhang
2021-06-17 15:42 ` Jing Zhang
2021-06-17 15:42 ` Jing Zhang
2021-06-17 4:41 ` [PATCH v10 3/5] KVM: stats: Add documentation for binary statistics interface Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 5:52 ` Greg KH
2021-06-17 5:52 ` Greg KH
2021-06-17 5:52 ` Greg KH
2021-06-17 15:09 ` Jing Zhang
2021-06-17 15:09 ` Jing Zhang
2021-06-17 15:09 ` Jing Zhang
2021-06-17 5:56 ` Greg KH
2021-06-17 5:56 ` Greg KH
2021-06-17 5:56 ` Greg KH
2021-06-17 11:29 ` Paolo Bonzini
2021-06-17 11:29 ` Paolo Bonzini
2021-06-17 11:29 ` Paolo Bonzini
2021-06-17 11:42 ` Greg KH
2021-06-17 11:42 ` Greg KH
2021-06-17 11:42 ` Greg KH
2021-06-17 11:46 ` Paolo Bonzini
2021-06-17 11:46 ` Paolo Bonzini
2021-06-17 11:46 ` Paolo Bonzini
2021-06-17 15:45 ` Jing Zhang
2021-06-17 15:45 ` Jing Zhang
2021-06-17 15:45 ` Jing Zhang
2021-06-17 15:20 ` Jing Zhang
2021-06-17 15:20 ` Jing Zhang
2021-06-17 15:20 ` Jing Zhang
2021-06-17 22:15 ` Jing Zhang
2021-06-17 22:15 ` Jing Zhang
2021-06-17 22:15 ` Jing Zhang
2021-06-17 6:05 ` Greg KH
2021-06-17 6:05 ` Greg KH
2021-06-17 6:05 ` Greg KH
2021-06-17 15:41 ` Jing Zhang
2021-06-17 15:41 ` Jing Zhang
2021-06-17 15:41 ` Jing Zhang
2021-06-17 6:07 ` Greg KH
2021-06-17 6:07 ` Greg KH
2021-06-17 6:07 ` Greg KH
2021-06-17 11:19 ` Paolo Bonzini
2021-06-17 11:19 ` Paolo Bonzini
2021-06-17 11:19 ` Paolo Bonzini
2021-06-17 11:34 ` Greg KH
2021-06-17 11:34 ` Greg KH
2021-06-17 11:34 ` Greg KH
2021-06-17 15:51 ` Jing Zhang
2021-06-17 15:51 ` Jing Zhang
2021-06-17 15:51 ` Jing Zhang
2021-06-17 4:41 ` [PATCH v10 4/5] KVM: selftests: Add selftest for KVM statistics data binary interface Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` [PATCH v10 5/5] KVM: stats: Remove code duplication for binary and debugfs stats Jing Zhang
2021-06-17 4:41 ` Jing Zhang
2021-06-17 4:41 ` Jing Zhang
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