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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3AA8C41513 for ; Wed, 16 Aug 2023 14:17:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343545AbjHPORJ (ORCPT ); Wed, 16 Aug 2023 10:17:09 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58290 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1343566AbjHPORB (ORCPT ); Wed, 16 Aug 2023 10:17:01 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A73352708 for ; Wed, 16 Aug 2023 07:17:00 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d68c0f22fc9so8015347276.0 for ; Wed, 16 Aug 2023 07:17:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20221208; t=1692195420; x=1692800220; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=mWxq8XPPN3K2/Hl7/jGuCvbco+UzQfaTP/jtlKOAWpo=; b=W5RkvSqWtUqZtUjB2ze0doBKoggpcspjyiMRkYklWTf2haqW9D9sSHYqoxAR18toeV 2z9RYXIQjIj556tedMIJq3rAO+1Rw8GZcPOBmo6B3a1I3Wjzq+KMVwGbzsVpQvXh+AoO ad88pJQ9ht+/z//hgVJjtmN5SMFBtESxC3hF81opZvsKtl/wqYtcakAJBiluJrg2THKY pnEZZtVLlL3BuK2DyiCZxa+DekBOKl9UpUpX6OG2kGPSR90KorX78VExiMh4yhXRPDj3 IEe1AbQhYVYcMHjyresqIt6W2/Bfj4WjrRe3mJLCzQKIxtXengvAm5xnmHMtao8ARbdd 7Nyw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1692195420; x=1692800220; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=mWxq8XPPN3K2/Hl7/jGuCvbco+UzQfaTP/jtlKOAWpo=; b=M7u7dhRX85Ptb19k5R7thLBr3MzqaylIwp+bUBWHaWPtElX+qODsyoEH1SjzvsaWvi 0QHuUOkTz7D+Ut+b6mv/qBtFK36lkWxm436YNKSdUPW4WjO/P/Zy0wNBy56ouNamoUH0 eutiIdQadO5EnC5J5lk3JD5hW117dp4avjJsD5kNzGdJn2enxELMjtmp9t6dXep6q9mo ziW6B5PXuilNOUzMWllIHw/Z9oTrFoX6ijchhOJnoNc5c2FAkc5fCwqcBdcfvu09MQmW J8c86yedmbrA5ixs/qFQcMszH5vTx1iW72AKv+i+EfoP4dx4BofzD+hPwIRidAw551h5 da4Q== X-Gm-Message-State: AOJu0Yz4ie+cSPz9v31lzOmNUmPVyAVX7446vlMLd7jKJ+bkGLw3wbfE K2k14KOIOySm7wl4xX/CKl+CC5ugaOU= X-Google-Smtp-Source: AGHT+IGheELvBADZ/ZGgycp9hodD4csVOu7LpxIxavoM/BdHmL+oISGRpZgvo+gyeVlsTmNsJnvzHTff28k= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1785:b0:d64:9e2c:5c0d with SMTP id ca5-20020a056902178500b00d649e2c5c0dmr77206ybb.5.1692195419994; Wed, 16 Aug 2023 07:16:59 -0700 (PDT) Date: Wed, 16 Aug 2023 14:16:58 +0000 In-Reply-To: Mime-Version: 1.0 References: Message-ID: Subject: Re: 5.10.189 and 5.10.190 breaks nested virtualization From: Sean Christopherson To: "Dr. David Alan Gilbert" Cc: Blair Strater , Vitaly Kuznetsov , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 16, 2023, Dr. David Alan Gilbert wrote: > * Blair Strater (strater@protonmail.com) wrote: > > Per the request at https://lwn.net/Articles/940798/, I'm reaching out to > > let you know that this patch breaks nested virtualization on AMD > > processors. > > > > I've tested 5.10.189 and 5.10.190 on the "outer" virtual host, and both > > Debian 12 running libvirt, and Proxmox 7 as "inner" hosts. For Debian, the > > nested VM fails to start at all, and consumes the entirety of one CPU core. > > For Proxmox, 100-200MB/second of memory is allocated and never released, > > and also the guest fails to start. The problems go away when taking the > > outer host back to 5.10.188. > > > > The processor in question is a Ryzen 7 2700. The kernel revision for > > Proxmox is 5.15.108-1-pve, and the kernel revision for Debian 12 is > > 6.1.0-11-amd64. I've run into another person who can confirm that this bug > > also occurs in the 6.4 series, "somewhere between 6.4.3 and 6.4.9", 6.4.9 > > being the likely culprit. > > > > Please let me know if you need any other information. > > > > I apologize for bothering an entire mailing list, Greg's email bot told me to. > > cc'd in Vitaly (who I notice was working another regression bug in > the recent stables), and Sean (who I notice has an L2 patch in the > 5.10.189..190 set). Does running with "spec_rstack_overflow=off" fix things for you? If so, can you then try testing the fix for the guest RFLAGS corruption[1]? It's a bit of a long shot, but I'm hoping we'll get lucky and all of these nested SVM errors[2] are just weird symptoms of branches going awry. [1] https://lore.kernel.org/all/20230811155255.250835-1-seanjc@google.com [2] https://bugzilla.kernel.org/show_bug.cgi?id=217796