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=-2.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 761A2C38A29 for ; Fri, 17 Apr 2020 10:56:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 57917221EC for ; Fri, 17 Apr 2020 10:56:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1587120974; bh=eE0mKh+guDz7kaVBZ5TP3KTi/3uxhOxlVLRn/H49upM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=KnAHAANA/ntxA3kX4yak50zRTx4tmZcnJVDmzrqV77lev5+9Y9pEdNiHt6EQNShyA W6BOCKZiahUgVW5YgJTl033SGwIvudwRl4xcaXGF1IdHd9bPgxAmYRfw/7J9eaULHj Ef5UVpievZstrl3jmHEORx33MwKxwKYi4brU50RA= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729980AbgDQK4N (ORCPT ); Fri, 17 Apr 2020 06:56:13 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:44743 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729869AbgDQK4D (ORCPT ); Fri, 17 Apr 2020 06:56:03 -0400 Received: by mail-wr1-f67.google.com with SMTP id d17so2504021wrg.11; Fri, 17 Apr 2020 03:56:01 -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:user-agent; bh=DYBfnvCIOfbYBUVMhiD0yzR/vj6W91VzUhD7daIMuuQ=; b=Fz87rzfr+tPDN7+DwmWt+/vz7NG+69QbDYIkkaaAs7elfggHSuyOX7LyvI7Y8h7Xkn +k+f2AqR3Itpu/l75Gq30oAjIAmPc/UR27FjuswUs+M8NOMYw2OFn9eFB2M8+/+Xpoba meRIWYD8ZLdogNHlydNeJtURXAzpys63ZaVKMLcXH2BhBCOvKDKkftRe+pQ/DV4QgRdy g1gidDVYKXtOYurIBLcMY3D1IjUKg6SKEWE4gkJwaF2AI7FuAsmZpJzzaHdI3ReUMP3M lG+FNgky1tqTb7L3RtFT63yhGq1ZYmRh/MP+eqWU+4NBonllaQKh0QFZ0NtqHlpJbpE8 7OEQ== X-Gm-Message-State: AGi0PuahG5Xd4GLKKoOsWS41BCy3cMv9KB6TI4Nlsgvb+3mQGjEOknQB FQADxcFkrDnEnyXCq7BJUeU= X-Google-Smtp-Source: APiQypK+ym/LoPqHMBZkBeU5WlMnH11OJtjXwSV8yRp3na8YAM9BOJIpCCmi2W1RtJxLUfAfdbHtbA== X-Received: by 2002:adf:eec8:: with SMTP id a8mr3121013wrp.28.1587120960891; Fri, 17 Apr 2020 03:56:00 -0700 (PDT) Received: from debian (44.142.6.51.dyn.plus.net. [51.6.142.44]) by smtp.gmail.com with ESMTPSA id h26sm7223748wmb.19.2020.04.17.03.55.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Apr 2020 03:56:00 -0700 (PDT) Date: Fri, 17 Apr 2020 11:55:58 +0100 From: Wei Liu To: Vitaly Kuznetsov Cc: Dexuan Cui , bp@alien8.de, haiyangz@microsoft.com, hpa@zytor.com, kys@microsoft.com, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org, mingo@redhat.com, sthemmin@microsoft.com, tglx@linutronix.de, x86@kernel.org, mikelley@microsoft.com, wei.liu@kernel.org, kvm@vger.kernel.org Subject: Re: [PATCH] x86/hyperv: Suspend/resume the VP assist page for hibernation Message-ID: <20200417105558.2jkqq2lih6vvoip2@debian> References: <1587104999-28927-1-git-send-email-decui@microsoft.com> <87blnqv389.fsf@vitty.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87blnqv389.fsf@vitty.brq.redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 17, 2020 at 12:03:18PM +0200, Vitaly Kuznetsov wrote: > Dexuan Cui writes: > > > Unlike the other CPUs, CPU0 is never offlined during hibernation. So in the > > resume path, the "new" kernel's VP assist page is not suspended (i.e. > > disabled), and later when we jump to the "old" kernel, the page is not > > properly re-enabled for CPU0 with the allocated page from the old kernel. > > > > So far, the VP assist page is only used by hv_apic_eoi_write(). > > No, not only for that ('git grep hv_get_vp_assist_page') > > KVM on Hyper-V also needs VP assist page to use Enlightened VMCS. In > particular, Enlightened VMPTR is written there. > > This makes me wonder: how does hibernation work with KVM in case we use > Enlightened VMCS and we have VMs running? We need to make sure VP Assist > page content is preserved. The page itself is preserved, isn't it? hv_cpu_die never frees the vp_assit page. It merely disables it. hv_cpu_init only allocates a new page if necessary. Wei. > > -- > Vitaly >