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From: Christophe de Dinechin <christophe.de.dinechin@gmail.com>
To: Liran Alon <liran.alon@oracle.com>
Cc: Christophe de Dinechin <christophe.de.dinechin@gmail.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	KVM list <kvm@vger.kernel.org>,
	x86@kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
	Jim Mattson <jmattson@google.com>,
	open list <linux-kernel@vger.kernel.org>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Peter Zijlstra (Intel)" <peterz@infradead.org>
Subject: Re: [PATCH RFC] KVM: x86: tell guests if the exposed SMT topology is trustworthy
Date: Fri, 8 Nov 2019 16:35:17 +0100	[thread overview]
Message-ID: <E392C60C-A596-49DD-B604-8B3C473ACAA2@dinechin.org> (raw)
In-Reply-To: <713ECF67-6A6C-4956-8AC6-7F4C05961328@oracle.com>



> On 7 Nov 2019, at 16:02, Liran Alon <liran.alon@oracle.com> wrote:
> 
> 
> 
>> On 7 Nov 2019, at 16:00, Christophe de Dinechin <christophe.de.dinechin@gmail.com> wrote:
>> 
> 
>> 
>> I share that concern about the naming, although I do see some
>> value in exposing the cpu_smt_possible() result. I think it’s easier
>> to state that something does not work than to state something does
>> work.
>> 
>> Also, with respect to mitigation, we may want to split the two cases
>> that Paolo outlined, i.e. have KVM_HINTS_REALTIME,
>> KVM_HINTS_CORES_CROSSTALK and
>> KVM_HINTS_CORES_LEAKING,
>> where CORES_CROSSTALKS indicates there may be some
>> cross-talk between what the guest thinks are isolated cores,
>> and CORES_LEAKING indicates that cores may leak data
>> to some other guest.
>> 
>> The problem with my approach is that it is shouting “don’t trust me”
>> a bit too loudly.
> 
> I don’t see a value in exposing CORES_LEAKING to guest. As guest have nothing to do with it.

The guest could display / expose the information to guest sysadmins
and admin tools (e.g. through /proc).

While the kernel cannot mitigate, a higher-level product could for example
have a policy about which workloads can be deployed on a system which
may leak data to other VMs.

Christophe

  reply	other threads:[~2019-11-08 15:35 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-05 16:17 [PATCH RFC] KVM: x86: tell guests if the exposed SMT topology is trustworthy Vitaly Kuznetsov
2019-11-05 17:17 ` Liran Alon
2019-11-05 17:30   ` Liran Alon
2019-11-05 17:35     ` Jim Mattson
2019-11-05 19:37 ` Sean Christopherson
2019-11-05 23:25   ` Sean Christopherson
2019-11-07 10:38     ` Vitaly Kuznetsov
     [not found]     ` <943488A8-2DD7-4471-B3C7-9F21A0B0BCF9@dinechin.org>
2019-11-07 15:02       ` Liran Alon
2019-11-08 15:35         ` Christophe de Dinechin [this message]
2019-11-08 15:52           ` Liran Alon
2019-11-05 20:02 ` Peter Zijlstra
2019-11-05 23:25   ` Sean Christopherson
2019-11-06  8:32     ` Peter Zijlstra
2019-11-20 10:13       ` Wanpeng Li
2019-11-05 23:51   ` Paolo Bonzini
2019-11-06  8:32     ` Peter Zijlstra
2019-11-06  9:41       ` Paolo Bonzini
2019-11-05 23:56 ` Paolo Bonzini
2019-12-06  4:01   ` Ankur Arora
2019-12-06 13:46     ` Vitaly Kuznetsov
2019-12-06 20:31       ` Ankur Arora
2019-12-09  9:15         ` Paolo Bonzini

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