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 1/2] KVM: x86: implement KVM_SET_TSC_PRECISE/KVM_GET_TSC_PRECISE
Date: Mon, 30 Nov 2020 15:33:46 +0100 [thread overview]
Message-ID: <38602ef4-7ecf-a5fd-6db9-db86e8e974e4@redhat.com> (raw)
In-Reply-To: <20201130133559.233242-2-mlevitsk@redhat.com>
On 30/11/20 14:35, Maxim Levitsky wrote:
> + if (guest_cpuid_has(vcpu, X86_FEATURE_TSC_ADJUST)) {
> + tsc_state.tsc_adjust = vcpu->arch.ia32_tsc_adjust_msr;
> + tsc_state.flags |= KVM_TSC_STATE_TSC_ADJUST_VALID;
> + }
This is mostly useful for userspace that doesn't disable the quirk, right?
> + kvm_get_walltime(&wall_nsec, &host_tsc);
> + diff = wall_nsec - tsc_state.nsec;
> +
> + if (diff < 0 || tsc_state.nsec == 0)
> + diff = 0;
> +
diff < 0 should be okay. Also why the nsec==0 special case? What about
using a flag instead?
Paolo
next prev parent reply other threads:[~2020-11-30 14:35 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 [this message]
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
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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