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Mon, 2 Jul 2018 07:32:58 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:38684 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1030331AbeGBLcy (ORCPT ); Mon, 2 Jul 2018 07:32:54 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 2E52D402333A; Mon, 2 Jul 2018 11:32:54 +0000 (UTC) Received: from [10.36.117.221] (ovpn-117-221.ams2.redhat.com [10.36.117.221]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 22B7A2166B5D; Mon, 2 Jul 2018 11:32:52 +0000 (UTC) Subject: Re: [PATCH v2 1/2] KVM: X86: Implement PV IPI in linux guest To: Wanpeng Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Vitaly Kuznetsov References: <1530526462-920-1-git-send-email-wanpengli@tencent.com> <1530526462-920-2-git-send-email-wanpengli@tencent.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; 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Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <1530526462-920-2-git-send-email-wanpengli@tencent.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 02 Jul 2018 11:32:54 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Mon, 02 Jul 2018 11:32:54 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'pbonzini@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/07/2018 12:14, Wanpeng Li wrote: > + unsigned long flags, ipi_bitmap_low = 0, ipi_bitmap_high = 0, icr = 0; > + int cpu, apic_id, ret = 1; > + > + if (cpumask_empty(mask)) > + return true; > + > + local_irq_save(flags); > + > + for_each_cpu(cpu, mask) { > + apic_id = per_cpu(x86_cpu_to_apicid, cpu); > + if (apic_id < BITS_PER_LONG) > + __set_bit(apic_id, &ipi_bitmap_low); > + else if (apic_id < 2 * BITS_PER_LONG) > + __set_bit(apic_id - BITS_PER_LONG, &ipi_bitmap_high); > + else > + goto ipi_mask_done; > + } CPU masks are themselves bitmaps made of longs, so you should be able to avoid the loop here. > +static void kvm_send_ipi_mask(const struct cpumask *mask, int vector) > +{ > + if (!__send_ipi_mask(mask, vector)) > + orig_apic.send_IPI_mask(mask, vector); > +} > + > +static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector) > +{ > + unsigned int this_cpu = smp_processor_id(); > + struct cpumask new_mask; > + const struct cpumask *local_mask; > + > + cpumask_copy(&new_mask, mask); > + cpumask_clear_cpu(this_cpu, &new_mask); > + local_mask = &new_mask; > + if (!__send_ipi_mask(local_mask, vector)) > + orig_apic.send_IPI_mask_allbutself(mask, vector); > +} Likewise, here it should be possible to check the highest bit in the mask before copying it. Paolo