From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pg1-f202.google.com (mail-pg1-f202.google.com [209.85.215.202]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA5081E8845 for ; Wed, 9 Oct 2024 15:58:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.215.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728489536; cv=none; b=OcGvVYz875+/oiRa5uVv+w/BlFWXSMhlcLK5dNmTaZWn1tLt1/yVlIGxDmGVv1/03bi3S62UM3Z99CvCCsV33D3GwBWs9VeBLuhr6bJjvgiz+QvfPKzZOD6Ml7RCTV6PkSfCBLRrQfnxXL7SQJ7cIRsLHfF451CipfCtaeFs6Ds= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728489536; c=relaxed/simple; bh=30NfKZLT1MP0Qf5dqi1pKIQDdlau/ThSQgfyAgM6+P8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=CQB/fNezAkUEPHE3hi6QH/W11gW88IdDn03uBE3YanTIc2UAvcqj+2ACpEuc4qMK4gTD2MWTq0OsV7f4t3jrHsGajH4m3JONj29UVl+ZnGUc7HM+8/n1wBQTzkSrdINItCsTUAg3ZgZomF3BN/y4MveFof3nYVpCq+6u40zgvz8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=efDQlFm8; arc=none smtp.client-ip=209.85.215.202 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="efDQlFm8" Received: by mail-pg1-f202.google.com with SMTP id 41be03b00d2f7-7c6a9c1a9b8so4286985a12.0 for ; Wed, 09 Oct 2024 08:58:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1728489534; x=1729094334; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=Ts8G/W/YzP17g23owGIref200B1OWyhLngxKHV0B+lc=; b=efDQlFm8MZCaJHxQvWjUxPJb2fxRycc2wUyJIHIoItp2DIqmreaiAZi4BDk0Jjsptq srXKWdF8i/0XS531f2tU9qD1tEJHww8WYaKB4h9wPbcWwwpNk3NliSLo9yUCnGDITFjB jcGjI+fFauUmGXj8RFLMVvueuxttyZ+HuvZ5KmgYhlKAfNVo4a9dpKw4ogDyp9N0Miab 07L4w6jtODKYexhbAr6t9b+9/eTSr3BHCWYErGYQLTUjJ4etcaTEYnLMi7T+1BOK/ron tchEyuto1i+epfCba3NH5WmaGfCSEgNBkQ6BN2y2ps3TWGqlsfhV/djZplEQKx3p1Ory OldA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1728489534; x=1729094334; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=Ts8G/W/YzP17g23owGIref200B1OWyhLngxKHV0B+lc=; b=NNIWODfMKUaNgB+9/4DBQK3JonYfCnXh9dg432NApxewypHvMvLzrdACvKW/vwbbNI WxP2sGImfkSvd18yfFiSLhDfCJhwmmlkZscfYAqxu7ZO3jIebGFm4vhH+9pJZ7Oy09WV BymwX21D37LzyE8uTA55p8SAmAjblIiiNNnhOUeLZMIWUE2cE5czKB4abd6YC/acHpvT zO1vpKTIDOvVOiGmB5O/6kOJY5NjZtrLaacqWn0DpjNs1SMHDqAKRtl7G5xVHlAnCyPr wwapE6WgbE+JVwJz5ol4qibuD3yzVL8YAgR0jyzX4rB97EhONzKoDHzlVnaUAeDMpIFc dPtg== X-Forwarded-Encrypted: i=1; AJvYcCU8VzCXi+1cMDDf1m0pqvfne1Dd4cvnALeHjxyqJI94aHRcQEINob8ZyWl16tGUDCJXBis=@vger.kernel.org X-Gm-Message-State: AOJu0YxfZUUsWxud5hEyZqsWCboGFqzAjEv0spuOZScYOA406/NuFeeB vvE7BLRVwxTkOCUEdJ1tzXOif0SDpiP+EySHQ7Vw5o9uQqPhCidmnPpFiaBBlKv/ZUTMTJa6GO2 r1g== X-Google-Smtp-Source: AGHT+IErBgFQtjMZqfp0oDNhjjbYCy24dN9A+KXRX4mSCBJh5Vs/DdeBKoJmqZriJq7aAZ+opCLOPUMDfz0= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:9d:3983:ac13:c240]) (user=seanjc job=sendgmr) by 2002:a65:408b:0:b0:7c6:af2b:196f with SMTP id 41be03b00d2f7-7ea320d7ddamr3399a12.6.1728489533794; Wed, 09 Oct 2024 08:58:53 -0700 (PDT) Date: Wed, 9 Oct 2024 08:58:52 -0700 In-Reply-To: <20241009092850.197575-17-nikunj@amd.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20241009092850.197575-1-nikunj@amd.com> <20241009092850.197575-17-nikunj@amd.com> Message-ID: Subject: Re: [PATCH v12 16/19] x86/kvmclock: Use clock source callback to update kvm sched clock From: Sean Christopherson To: Nikunj A Dadhania Cc: linux-kernel@vger.kernel.org, thomas.lendacky@amd.com, bp@alien8.de, x86@kernel.org, kvm@vger.kernel.org, mingo@redhat.com, tglx@linutronix.de, dave.hansen@linux.intel.com, pgonda@google.com, pbonzini@redhat.com Content-Type: text/plain; charset="us-ascii" On Wed, Oct 09, 2024, Nikunj A Dadhania wrote: > Although the kernel switches over to stable TSC clocksource instead of > kvmclock, the scheduler still keeps on using kvmclock as the sched clock. > This is due to kvm_sched_clock_init() updating the pv_sched_clock() > unconditionally. All PV clocks are affected by this, no? This seems like something that should be handled in common code, which is the point I was trying to make in v11. > Use the clock source enable/disable callbacks to initialize > kvm_sched_clock_init() and update the pv_sched_clock(). > > As the clock selection happens in the stop machine context, schedule > delayed work to update the static_call() > > Signed-off-by: Nikunj A Dadhania > --- > arch/x86/kernel/kvmclock.c | 34 +++++++++++++++++++++++++++++----- > 1 file changed, 29 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c > index 5b2c15214a6b..5cd3717e103b 100644 > --- a/arch/x86/kernel/kvmclock.c > +++ b/arch/x86/kernel/kvmclock.c > @@ -21,6 +21,7 @@ > #include > #include > #include > +#include > > static int kvmclock __initdata = 1; > static int kvmclock_vsyscall __initdata = 1; > @@ -148,12 +149,39 @@ bool kvm_check_and_clear_guest_paused(void) > return ret; > } > > +static u64 (*old_pv_sched_clock)(void); > + > +static void enable_kvm_sc_work(struct work_struct *work) > +{ > + u8 flags; > + > + old_pv_sched_clock = static_call_query(pv_sched_clock); > + flags = pvclock_read_flags(&hv_clock_boot[0].pvti); > + kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT); > +} > + > +static DECLARE_DELAYED_WORK(enable_kvm_sc, enable_kvm_sc_work); > + > +static void disable_kvm_sc_work(struct work_struct *work) > +{ > + if (old_pv_sched_clock) This feels like it should be a WARN condition, as IIUC, pv_sched_clock() should never be null. And it _looks_ wrong too, as it means kvm_clock will remain the sched clock if there was no old clock, which should be impossible. > + paravirt_set_sched_clock(old_pv_sched_clock);