From: Paolo Bonzini <pbonzini@redhat.com>
To: Maxim Levitsky <mlevitsk@redhat.com>, kvm@vger.kernel.org
Cc: Oliver Upton <oupton@google.com>, Ingo Molnar <mingo@redhat.com>,
Sean Christopherson <sean.j.christopherson@intel.com>,
Thomas Gleixner <tglx@linutronix.de>,
open list <linux-kernel@vger.kernel.org>,
Marcelo Tosatti <mtosatti@redhat.com>,
Jonathan Corbet <corbet@lwn.net>,
Wanpeng Li <wanpengli@tencent.com>,
Borislav Petkov <bp@alien8.de>, Jim Mattson <jmattson@google.com>,
"H. Peter Anvin" <hpa@zytor.com>,
"open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
Joerg Roedel <joro@8bytes.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH 2/2] KVM: x86: introduce KVM_X86_QUIRK_TSC_HOST_ACCESS
Date: Mon, 30 Nov 2020 15:15:11 +0100 [thread overview]
Message-ID: <5e77e912-893b-0c8f-a9a6-b43eaee24ed3@redhat.com> (raw)
In-Reply-To: <638a2919cf7c11c55108776beecafdd8e2da2995.camel@redhat.com>
On 30/11/20 15:11, Maxim Levitsky wrote:
> On Mon, 2020-11-30 at 14:54 +0100, Paolo Bonzini wrote:
>> On 30/11/20 14:35, Maxim Levitsky wrote:
>>> This quirk reflects the fact that we currently treat MSR_IA32_TSC
>>> and MSR_TSC_ADJUST access by the host (e.g qemu) in a way that is different
>>> compared to an access from the guest.
>>>
>>> For host's MSR_IA32_TSC read we currently always return L1 TSC value, and for
>>> host's write we do the tsc synchronization.
>>>
>>> For host's MSR_TSC_ADJUST write, we don't make the tsc 'jump' as we should
>>> for this msr.
>>>
>>> When the hypervisor uses the new TSC GET/SET state ioctls, all of this is no
>>> longer needed, thus leave this enabled only with a quirk
>>> which the hypervisor can disable.
>>>
>>> Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
>>> Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
>>
>> This needs to be covered by a variant of the existing selftests testcase
>> (running the same guest code, but different host code of course).
> Do you think that the test should go to the kernel's kvm unit tests,
> or to kvm-unit-tests project?
The latter already has x86_64/tsc_msrs_test.c (which I created in
preparation for this exact change :)).
Paolo
next prev parent reply other threads:[~2020-11-30 14:17 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-30 13:35 [PATCH 0/2] RFC: Precise TSC migration Maxim Levitsky
2020-11-30 13:35 ` [PATCH 1/2] KVM: x86: implement KVM_SET_TSC_PRECISE/KVM_GET_TSC_PRECISE Maxim Levitsky
2020-11-30 14:33 ` Paolo Bonzini
2020-11-30 15:58 ` Maxim Levitsky
2020-11-30 17:01 ` Paolo Bonzini
2020-12-01 19:43 ` Thomas Gleixner
2020-12-03 11:11 ` Maxim Levitsky
2020-11-30 13:35 ` [PATCH 2/2] KVM: x86: introduce KVM_X86_QUIRK_TSC_HOST_ACCESS Maxim Levitsky
2020-11-30 13:54 ` Paolo Bonzini
2020-11-30 14:11 ` Maxim Levitsky
2020-11-30 14:15 ` Paolo Bonzini [this message]
2020-11-30 15:33 ` Maxim Levitsky
2020-11-30 13:38 ` [PATCH 0/2] RFC: Precise TSC migration (summary) Maxim Levitsky
2020-11-30 16:54 ` [PATCH 0/2] RFC: Precise TSC migration Andy Lutomirski
2020-11-30 16:59 ` Paolo Bonzini
2020-11-30 19:16 ` Marcelo Tosatti
2020-12-01 12:30 ` Maxim Levitsky
2020-12-01 19:48 ` Marcelo Tosatti
2020-12-03 11:39 ` Maxim Levitsky
2020-12-03 20:18 ` Marcelo Tosatti
2020-12-07 13:00 ` Maxim Levitsky
2020-12-01 13:48 ` Thomas Gleixner
2020-12-01 15:02 ` Marcelo Tosatti
2020-12-03 11:51 ` Maxim Levitsky
2020-12-01 14:01 ` Thomas Gleixner
2020-12-01 16:19 ` Andy Lutomirski
2020-12-03 11:57 ` Maxim Levitsky
2020-12-01 19:35 ` Thomas Gleixner
2020-12-03 11:41 ` Paolo Bonzini
2020-12-03 12:47 ` Maxim Levitsky
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