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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id DEA91C433F5 for ; Wed, 13 Oct 2021 06:26:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BF45961027 for ; Wed, 13 Oct 2021 06:26:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237918AbhJMG2r (ORCPT ); Wed, 13 Oct 2021 02:28:47 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:30242 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230001AbhJMG2q (ORCPT ); Wed, 13 Oct 2021 02:28:46 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1634106403; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=M1r4UVSywHFrxKSzRmoAA2AVvVNlTRcwY3Az5uiDbcY=; b=LhGUiMm5EvVInZ4nW1mpWH7Yz3cP8nWdciDPmvJQE9SuYt5Sl5sH+SwVA3YtJd0AWd3Jeo sdApowZ/QCuoSBybGk875V3n0UqDs7V9VrxnpfrCK/hmv7SI48pQgd83qRMYHaABgXkZyr DM/m95cBu6FdbJKUXE3602KfFTZN1/U= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-491-WbWGXxEoN5-zPF6PNg8OJw-1; Wed, 13 Oct 2021 02:26:41 -0400 X-MC-Unique: WbWGXxEoN5-zPF6PNg8OJw-1 Received: by mail-ed1-f72.google.com with SMTP id e14-20020a056402088e00b003db6ebb9526so1242517edy.22 for ; Tue, 12 Oct 2021 23:26:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=M1r4UVSywHFrxKSzRmoAA2AVvVNlTRcwY3Az5uiDbcY=; b=rIWYOjkZ04EnbSXjVqctk1SHGOE19VuoJ6LsecqbEKjZ1DqQTkM4T4V1FvXm+mdUfz F9G0y5E/nsxv4/GUXbn+SQfoNwM7Q/85BOuykFTwo7fSiHb6f5fxK5ZJGETQSatuezD5 O861SgtroHKFPO4pL6xMiTQtT9aDVjg0OiFLHvY/7TCIcdh03K1ETPOzABuWBncBl5gk wEWL6wsqo5TIOMCyfeLhOF+hL9CnoGxQ6hZvMRKEy7VeAl5+2UgA1XvWbb4o4Iu6kebe 5UJSiUNjvQUhdotmVNOCHem2LnYz5J9Fp2M8VllpFFG7fUclTvm7u3+CPNNVbxyTEhOk EPBQ== X-Gm-Message-State: AOAM531Cp5lWpKsJci3ylLvXKTkS31cZaHCLZqHkUQLWEhUkex6IXn+t KnYeZZH/J2mo9PG4EBfiaMWVvChIPcR4mn14BXVOyw01eYZgdutD6TiobU1GE0ClUo57WNvo0d6 7/ESEMPRH/ofX X-Received: by 2002:a17:906:3715:: with SMTP id d21mr39321986ejc.74.1634106400732; Tue, 12 Oct 2021 23:26:40 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwXXcXln6n4WTKAKDJCP/hvAKxCAGfx3dk26i18CyUdzkB601fhOGjD+CKgtZgBhVGNamrRdQ== X-Received: by 2002:a17:906:3715:: with SMTP id d21mr39321958ejc.74.1634106400457; Tue, 12 Oct 2021 23:26:40 -0700 (PDT) Received: from ?IPV6:2001:b07:6468:f312:c8dd:75d4:99ab:290a? ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id k19sm5933406ejg.13.2021.10.12.23.26.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 12 Oct 2021 23:26:39 -0700 (PDT) Message-ID: <0962c143-2ff9-f157-d258-d16659818e80@redhat.com> Date: Wed, 13 Oct 2021 08:26:36 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.1.0 Subject: Re: [patch 13/31] x86/fpu: Move KVMs FPU swapping to FPU core Content-Language: en-US To: "Liu, Jing2" , Thomas Gleixner , LKML Cc: "x86@kernel.org" , "Bae, Chang Seok" , Dave Hansen , Arjan van de Ven , "kvm@vger.kernel.org" , "Nakajima, Jun" , Jing Liu , "seanjc@google.com" References: <20211011215813.558681373@linutronix.de> <20211011223611.069324121@linutronix.de> <8a5762ab-18d5-56f8-78a6-c722a2f387c5@redhat.com> From: Paolo Bonzini In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 13/10/21 08:15, Liu, Jing2 wrote: > After KVM passthrough XFD to guest, when vmexit opening > irq window and KVM is interrupted, kernel softirq path can call > kernel_fpu_begin() to touch xsave state. This function does > XSAVES. If guest XFD[18] is 1, and with guest AMX state in register, > then guest AMX state is lost by XSAVES. Yes, the host value of XFD (which is zero) has to be restored after vmexit. See how KVM already handles SPEC_CTRL. Passthrough of XFD is only enabled after the guest has caused an #NM vmexit and the full XSAVE state has been dynamically allocated, therefore it is always possible to do an XSAVES even from atomic context. Paolo