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=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no 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 3C2DCC4332B for ; Mon, 23 Mar 2020 21:58:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 081F7207FC for ; Mon, 23 Mar 2020 21:58:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="SaOh6IUn" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727122AbgCWV6x (ORCPT ); Mon, 23 Mar 2020 17:58:53 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:38824 "EHLO us-smtp-delivery-74.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725990AbgCWV6x (ORCPT ); Mon, 23 Mar 2020 17:58:53 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585000732; 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=zrfYR5Mq4/pcFfLsa/LVNTAJa62E45cyd+8qzOhvSWg=; b=SaOh6IUnmhnRCCShK7OBy+cqQvSLREkfN0WTDZj5VnbjhGT9N3urxuA4nDW+g9Mkijf/zC kM/CceGnNEThJJFpu2DhJCzss1TLpaRo7jYpC4NSdnhp/kHxXQUSnaq2O5axExYjlGJDAK OeA1DPOkHP3JIsoLb1Bdh5SBXDEmCNE= Received: from mail-wr1-f69.google.com (mail-wr1-f69.google.com [209.85.221.69]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-225-wGOFFR_eOx2DBhGjn2MNHQ-1; Mon, 23 Mar 2020 17:58:50 -0400 X-MC-Unique: wGOFFR_eOx2DBhGjn2MNHQ-1 Received: by mail-wr1-f69.google.com with SMTP id d17so8136586wrw.19 for ; Mon, 23 Mar 2020 14:58:50 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=zrfYR5Mq4/pcFfLsa/LVNTAJa62E45cyd+8qzOhvSWg=; b=R3GTk9sJuP5wfHgYJwIg7jorE/mxMpbKN4kwGRYfqXPc8cg7Xw+EfGDbh4arIRvc62 wc4fcWLsaue3c3NnSCDfOD7huSja6lNXnuzKVM7wbEwQ1phf1darVGN4QycKfgPn6b1z E0ztPWjlXbLTX2VGJV/W51U5CN2yzeRQczYI0+efw86gNpq/keuKgynnrZt54Qu8/t92 OXO5RgjUvZaM542Ww59YIbBgbLHzDNn647CT4Ya7BVmC7BFNG4MmzgR9rEqP4AU32hjF wpuht3jCKJHLQ3Yf6IRhqxlOVXLMqrZirYAF3BPeWGvuHcwkd5pCV+ky1ExrehJE0zG3 95dA== X-Gm-Message-State: ANhLgQ1UBvJsMrDmvFDU02lH8lsAwnSqnWmyccwXcTdckbgaZytLqdv+ lc8S5IUKAD/DuVqH3H7EZcvKmpo0KNVWFW/YbrvFnnwdFABDmO80k4DZarQj71s1ZO2IAKRwrzZ EMPo3Ql4DapZSAQFQjb5fQ+1A X-Received: by 2002:a05:6000:100f:: with SMTP id a15mr30695178wrx.382.1585000729464; Mon, 23 Mar 2020 14:58:49 -0700 (PDT) X-Google-Smtp-Source: ADFU+vtET33cycpmBlukNFuklN1WSVqsTdfPc043Kg05YB8fRQsvxJluzmQGxGP1uB2QGW88BmLZgQ== X-Received: by 2002:a05:6000:100f:: with SMTP id a15mr30695156wrx.382.1585000729157; Mon, 23 Mar 2020 14:58:49 -0700 (PDT) Received: from xz-x1 ([2607:9880:19c0:32::2]) by smtp.gmail.com with ESMTPSA id p22sm1224886wmg.37.2020.03.23.14.58.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Mar 2020 14:58:48 -0700 (PDT) Date: Mon, 23 Mar 2020 17:58:44 -0400 From: Peter Xu To: Sean Christopherson Cc: Christian Borntraeger , Janosch Frank , Paolo Bonzini , David Hildenbrand , Cornelia Huck , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Qian Cai Subject: Re: [PATCH 7/7] KVM: selftests: Add "delete" testcase to set_memory_region_test Message-ID: <20200323215844.GS127076@xz-x1> References: <20200320205546.2396-1-sean.j.christopherson@intel.com> <20200320205546.2396-8-sean.j.christopherson@intel.com> <20200323190636.GM127076@xz-x1> <20200323214317.GV28711@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200323214317.GV28711@linux.intel.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 23, 2020 at 02:43:18PM -0700, Sean Christopherson wrote: > On Mon, Mar 23, 2020 at 03:06:36PM -0400, Peter Xu wrote: > > On Fri, Mar 20, 2020 at 01:55:46PM -0700, Sean Christopherson wrote: > > > + /* > > > + * Spin until the memory region is moved to a misaligned address. This > > > + * may or may not trigger MMIO, as the window where the memslot is > > > + * invalid is quite small. > > > + */ > > > + val = guest_spin_on_val(0); > > > + GUEST_ASSERT(val == 1 || val == MMIO_VAL); > > > + > > > + /* Spin until the memory region is realigned. */ > > > + GUEST_ASSERT(guest_spin_on_val(MMIO_VAL) == 1); > > > > IIUC ideally we should do GUEST_SYNC() after each GUEST_ASSERT() to > > make sure the two threads are in sync. Otherwise e.g. there's no > > guarantee that the main thread won't run too fast to quickly remove > > the memslot and re-add it back before the guest_spin_on_val() starts > > above, then the assert could trigger when it reads the value as zero. > > Hrm, I was thinking ucall wasn't available across pthreads, but it's just > dumped into a global variable. I'll rework this to replace the udelay() > hacks with proper synchronization. I think ucall should work for pthread (shared address space of either kvm_run or guest memories), however my thought was even simpler than that, something like: - in guest code: do GUEST_SYNC after each GUEST_ASSERT - introduce a global_sem - in vcpu thread: when receive GUEST_SYNC, do "sem_post(&global_sem)" - in main thread: replace all usleep() with "sem_wait(&global_sem)" -- Peter Xu