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From: Paolo Bonzini <pbonzini@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>, Oliver Upton <oupton@google.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
	kvm@vger.kernel.org, Will Deacon <will@kernel.org>,
	Peter Shier <pshier@google.com>, Marc Zyngier <maz@kernel.org>,
	David Matlack <dmatlack@google.com>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org,
	Jim Mattson <jmattson@google.com>
Subject: Re: [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace
Date: Fri, 1 Oct 2021 11:17:33 +0200	[thread overview]
Message-ID: <48151d08-ee29-2b98-b6e1-f3c8a1ff26bc@redhat.com> (raw)
In-Reply-To: <20210930191416.GA19068@fuller.cnet>

On 30/09/21 21:14, Marcelo Tosatti wrote:
>> +   new_off_n = t_0 + off_n + (k_1 - k_0) * freq - t_1
> Hi Oliver,
> 
> This won't advance the TSC values themselves, right?

Why not?  It affects the TSC offset in the vmcs, so the TSC in the VM is 
advanced too.

Paolo

> This (advancing the TSC values by the realtime elapsed time) would be
> awesome because TSC clock_gettime() vdso is faster, and some
> applications prefer to just read from TSC directly.
> See "x86: kvmguest: use TSC clocksource if invariant TSC is exposed".
> 
> The advancement with this patchset only applies to kvmclock.
> 

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  reply	other threads:[~2021-10-01  9:17 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-16 18:15 [PATCH v8 0/7] KVM: x86: Add idempotent controls for migrating system counter state Oliver Upton
2021-09-16 18:15 ` [PATCH v8 1/7] kvm: x86: abstract locking around pvclock_update_vm_gtod_copy Oliver Upton
2021-09-16 18:15 ` [PATCH v8 2/7] KVM: x86: extract KVM_GET_CLOCK/KVM_SET_CLOCK to separate functions Oliver Upton
2021-09-16 18:15 ` [PATCH v8 3/7] KVM: x86: Fix potential race in KVM_GET_CLOCK Oliver Upton
2021-09-29 13:33   ` Marcelo Tosatti
2021-09-16 18:15 ` [PATCH v8 4/7] KVM: x86: Report host tsc and realtime values " Oliver Upton
2021-09-28 18:53   ` Marcelo Tosatti
2021-09-29 11:20     ` Paolo Bonzini
2021-09-29 18:56   ` Marcelo Tosatti
2021-09-30 19:21     ` Marcelo Tosatti
2021-09-30 23:02       ` Thomas Gleixner
2021-10-01 12:05         ` Marcelo Tosatti
2021-10-01 12:10           ` Marcelo Tosatti
2021-10-01 19:59           ` Thomas Gleixner
2021-10-01 21:03             ` Oliver Upton
2021-10-01 14:17         ` Paolo Bonzini
2021-10-01 14:39   ` Paolo Bonzini
2021-10-01 14:41     ` Paolo Bonzini
2021-10-01 15:39       ` Oliver Upton
2021-10-01 16:42         ` Paolo Bonzini
2021-09-16 18:15 ` [PATCH v8 5/7] kvm: x86: protect masterclock with a seqcount Oliver Upton
2021-09-24 16:42   ` Paolo Bonzini
2021-09-30 17:51   ` Marcelo Tosatti
2021-10-01 16:48   ` Paolo Bonzini
2021-09-16 18:15 ` [PATCH v8 6/7] KVM: x86: Refactor tsc synchronization code Oliver Upton
2021-09-16 18:15 ` [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace Oliver Upton
2021-09-30 19:14   ` Marcelo Tosatti
2021-10-01  9:17     ` Paolo Bonzini [this message]
2021-10-01 10:32       ` Marcelo Tosatti
2021-10-01 15:12         ` Paolo Bonzini
2021-10-01 19:11           ` Marcelo Tosatti
2021-10-01 19:33             ` Oliver Upton
2021-10-04 14:30               ` Marcelo Tosatti
2021-10-04 11:44             ` Paolo Bonzini
2021-10-05 15:22   ` Sean Christopherson
2022-02-23 10:02   ` David Woodhouse
2021-09-24 16:43 ` [PATCH v8 0/7] KVM: x86: Add idempotent controls for migrating system counter state Paolo Bonzini

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