From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A9E3BE56F; Mon, 17 Mar 2025 13:13:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742217199; cv=none; b=NRjnboLoNNzlZM1CyLpm+KOAP9zIgqRa009CIzOmBw8N4zMYZ3jpyjYUiZ3aJznDX1T46S9euDMoI1BC4Lk9rRZWQvcqoyq31kaugRtVjvjdJyWXL1YcmzHPF6+Ug/b3OCJHh+47Iuk40ZOEExExLRA4D0WGr7Mf5Gm3xeaiUr4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1742217199; c=relaxed/simple; bh=HrQ1t1lZWKkN411EmfUJK1mObU5Vz+PQvyjN3wj4dEk=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=OKNptK2IA8urlOl5eP/JnIjk2ldNJOxrRxuII0aIaUZR5VyxjDm6/cke1gAabFLkgKoGyeeAf1ETMiyAV7OAHOg496zVjamwVW0wcqFrZE8YV4Ym6e8jsszbEEPZU0BnRKitSMce5PyEmRW9bQxsdrPh8N32v49s7y/TcqqykCI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=I0SC8sOL; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=TmU8ZwIB; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="I0SC8sOL"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="TmU8ZwIB" From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1742217195; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=elqP/dUEnChhUjOELroRy5eKXIUAe/WjjQGOV3HaO7E=; b=I0SC8sOLs+AxSv01xAJVjtiE24Zb1dXlw4LvNT6lz1AQU1YuIGyh3ivRHFRxCZn1NHXVsT Fo/xjNBSEIE2iN0/w8fGdYCvS6+8z7vBw7TN92oBiWu2nZFAwqQvrclovyKoHQUuN+UUyw XYQnTaX+Fo+8LtVrNe0C2weV18dqq2eYBA1M/pnQzGJg2JI5MICVloK6e/VNK3eirnF8vU 3jRuMoMcA+Qj04aOy52gE1X4HDNaHWEw8io7+63l+FoNhcPojw9dhL7Nw2tGjxJ3zSTs+p ptabCjrOAZ+J88B4XOqdNtIWKg0RMVcjvpejQXXrcscnYZm+uY6gMaiAAP96uw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1742217195; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=elqP/dUEnChhUjOELroRy5eKXIUAe/WjjQGOV3HaO7E=; b=TmU8ZwIBDgFSXy4f9Hkvc7e3MUDHrgOMWgcCHBnxX1G/So9RTTrqHB7Z7chCDGoB5lWjeD x4G4jNs//SoM48Dg== To: Sean Christopherson , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, Sean Christopherson , Paolo Bonzini Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Jacob Pan , Jim Mattson Subject: Re: [PATCH 2/8] x86/irq: Track if IRQ was found in PIR during initial loop (to load PIR vals) In-Reply-To: <20250315030630.2371712-3-seanjc@google.com> References: <20250315030630.2371712-1-seanjc@google.com> <20250315030630.2371712-3-seanjc@google.com> Date: Mon, 17 Mar 2025 14:13:15 +0100 Message-ID: <87wmcn4x78.ffs@tglx> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Fri, Mar 14 2025 at 20:06, Sean Christopherson wrote: > @@ -409,25 +409,28 @@ static __always_inline bool handle_pending_pir(u64 *pir, struct pt_regs *regs) > { > int i, vec = FIRST_EXTERNAL_VECTOR; > unsigned long pir_copy[4]; > - bool handled = false; > + bool found_irq = false; > > - for (i = 0; i < 4; i++) > + for (i = 0; i < 4; i++) { > pir_copy[i] = READ_ONCE(pir[i]); > + if (pir_copy[i]) > + found_irq = true; > + } That's four extra conditional branches. You can avoid them completely. See delta patch below. Thanks, tglx --- --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -407,17 +407,15 @@ void intel_posted_msi_init(void) */ static __always_inline bool handle_pending_pir(u64 *pir, struct pt_regs *regs) { + unsigned long pir_copy[4], pend = 0; int i, vec = FIRST_EXTERNAL_VECTOR; - unsigned long pir_copy[4]; - bool found_irq = false; for (i = 0; i < 4; i++) { pir_copy[i] = READ_ONCE(pir[i]); - if (pir_copy[i]) - found_irq = true; + pend |= pir_copy[i]; } - if (!found_irq) + if (!pend) return false; for (i = 0; i < 4; i++) {