From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Peter Zijlstra , Peng Hao , Paolo Bonzini , Sasha Levin Subject: [PATCH 4.14 191/217] kvmclock: fix TSC calibration for nested guests Date: Thu, 23 Aug 2018 09:55:04 +0200 Message-Id: <20180823075514.241182583@linuxfoundation.org> In-Reply-To: <20180823075505.090246914@linuxfoundation.org> References: <20180823075505.090246914@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.14-stable review patch. If anyone has any objections, please let me know. ------------------ From: Peng Hao [ Upstream commit e10f7805032365cc11c739a97f226ebb48aee042 ] Inside a nested guest, access to hardware can be slow enough that tsc_read_refs always return ULLONG_MAX, causing tsc_refine_calibration_work to be called periodically and the nested guest to spend a lot of time reading the ACPI timer. However, if the TSC frequency is available from the pvclock page, we can just set X86_FEATURE_TSC_KNOWN_FREQ and avoid the recalibration. 'refine' operation. Suggested-by: Peter Zijlstra Signed-off-by: Peng Hao [Commit message rewritten. - Paolo] Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- arch/x86/kernel/kvmclock.c | 1 + 1 file changed, 1 insertion(+) --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -143,6 +143,7 @@ static unsigned long kvm_get_tsc_khz(voi src = &hv_clock[cpu].pvti; tsc_khz = pvclock_tsc_khz(src); put_cpu(); + setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ); return tsc_khz; }