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([2001:b07:6468:f312:63a7:c72e:ea0e:6045]) by smtp.gmail.com with ESMTPSA id n186sm7166424wme.31.2021.10.01.02.17.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 01 Oct 2021 02:17:41 -0700 (PDT) Message-ID: <48151d08-ee29-2b98-b6e1-f3c8a1ff26bc@redhat.com> Date: Fri, 1 Oct 2021 11:17:33 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [PATCH v8 7/7] KVM: x86: Expose TSC offset controls to userspace To: Marcelo Tosatti , Oliver Upton References: <20210916181538.968978-1-oupton@google.com> <20210916181538.968978-8-oupton@google.com> <20210930191416.GA19068@fuller.cnet> From: Paolo Bonzini In-Reply-To: <20210930191416.GA19068@fuller.cnet> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=pbonzini@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Cc: Catalin Marinas , kvm@vger.kernel.org, Will Deacon , Peter Shier , Marc Zyngier , David Matlack , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, Jim Mattson X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu 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. > _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm