From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DF184C43141 for ; Fri, 29 Jun 2018 15:21:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 985862804F for ; Fri, 29 Jun 2018 15:21:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 985862804F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936575AbeF2PVw (ORCPT ); Fri, 29 Jun 2018 11:21:52 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:58964 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S936176AbeF2PVv (ORCPT ); Fri, 29 Jun 2018 11:21:51 -0400 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9087B40201C7; Fri, 29 Jun 2018 15:21:50 +0000 (UTC) Received: from vitty.brq.redhat.com.redhat.com (unknown [10.43.2.155]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A7DA776EA; Fri, 29 Jun 2018 15:21:48 +0000 (UTC) From: Vitaly Kuznetsov To: Roman Kagan Cc: kvm@vger.kernel.org, x86@kernel.org, Paolo Bonzini , Radim =?utf-8?B?S3LEjW3DocWZ?= , "K. Y. Srinivasan" , Haiyang Zhang , Stephen Hemminger , "Michael Kelley \(EOSG\)" , Mohammed Gamal , Cathy Avery , Wanpeng Li , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 3/5] KVM: x86: hyperv: use get_vcpu_by_vpidx() in kvm_hv_flush_tlb() References: <20180629141455.19525-1-vkuznets@redhat.com> <20180629141455.19525-4-vkuznets@redhat.com> <20180629150104.GE15656@rkaganb.sw.ru> Date: Fri, 29 Jun 2018 17:21:47 +0200 In-Reply-To: <20180629150104.GE15656@rkaganb.sw.ru> (Roman Kagan's message of "Fri, 29 Jun 2018 18:01:05 +0300") Message-ID: <87a7rdd3ec.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Fri, 29 Jun 2018 15:21:50 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.6]); Fri, 29 Jun 2018 15:21:50 +0000 (UTC) for IP:'10.11.54.5' DOMAIN:'int-mx05.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'vkuznets@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Roman Kagan writes: > On Fri, Jun 29, 2018 at 04:14:53PM +0200, Vitaly Kuznetsov wrote: >> VP_INDEX almost always matches VCPU id and get_vcpu_by_vpidx() is fast, >> use it instead of traversing full vCPU list every time. >> >> To support the change switch kvm_make_vcpus_request_mask() to checking >> vcpu_id instead of vcpu index, > > I'm afraid you can't do this: vcpu_id (== apic id) can be sparse, i.e. > it's not very well suited for bitmaps and can exceed the max number of > vcpus. True. The bitmap should be of KVM_MAX_VCPU_ID size, not KVM_MAX_VCPUS. Unfortunately there's no convenient way to get VCPU idx from VCPU id, kvm_vcpu_get_idx() just walks the whole list :-( I see two possible options: 1) Add vcpu_idx fields to struct kvm_vcpu 2) Keep the change expecting masks of KVM_MAX_VCPU_ID in kvm_make_vcpus_request_mask(). KVM_MAX_VCPU_ID is currently 1023 so our bitmaps will be 16 longs long. Not sure if it's too much. -- Vitaly