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 lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 0D539C05027 for ; Thu, 26 Jan 2023 23:53:42 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1pLC3A-0000mR-1g; Thu, 26 Jan 2023 18:53:00 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1pLC38-0000kU-0G for qemu-devel@nongnu.org; Thu, 26 Jan 2023 18:52:58 -0500 Received: from mail-qt1-x831.google.com ([2607:f8b0:4864:20::831]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1pLC36-0000r2-9K for qemu-devel@nongnu.org; Thu, 26 Jan 2023 18:52:57 -0500 Received: by mail-qt1-x831.google.com with SMTP id s4so2783769qtx.6 for ; Thu, 26 Jan 2023 15:52:55 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=koconnor.net; s=google; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date:from:to :cc:subject:date:message-id:reply-to; bh=UroPNeyGolPSc4AeIUJptAUxE2BU/L0w0GU3C1PJzJc=; b=KVRXSZlcq9t+wUG/QENleViQ72Qmw5LwKgEqKoPBm/sOgrjGjIkRYDp2+ZPwyO3B8I M0tTrWHY/Ps1cZxrrNYNcy/pQP5RqkiBilyAOW93nlovnDDp6Zf+YBHAfbvNRiSoPmWw Z00f58fy/xSV3sSdiuQ5iindJwIPSpUzJ4Fuk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=UroPNeyGolPSc4AeIUJptAUxE2BU/L0w0GU3C1PJzJc=; b=6hKQHO6OBe6pXrVHqsNHAyE5IzpHR8qDh0FIkFtEGGBUj9+V/RT+8igjtw39Et5mNv dqaHyuDqIa264cOa8uEy8ShXbE9NvzYxJ9LeOk5BFco4uJxr8vtoSS+ucAJlT6v5+GCj 1paje4uvpSr53MpAKaUUExh8jk/Hnf/zyz8hRdwnrJJAsc18dyUhlDuNCEDLHBJnrAdB qLLSE17nkCsKkk85NG3s4XXDwmvsi1PM72PgNhYdaWo6AvSxAHiy+V4u9euRdg/V2mO8 KNs6RBEPcNPcDRS9ZJTjLWpwta7fbiSOR9Ahgg44m9NmnLiumpmm0bsQnT+xvpYu/nDX lJlg== X-Gm-Message-State: AFqh2kpfnSoQPJqS0QwQOZYLGPktiZKGXGK/Ptty7Dv5Cv5XDq3zqSDI u1iUxitsa9CQDDoIRSyVrlbXwQ== X-Google-Smtp-Source: AMrXdXsrfVzASVRgvjjBI+Fccg+qIz2lwVVPSChxGQajRz8mS4PHXRer1c82HYJIpg8zeOQLroq52A== X-Received: by 2002:ac8:4a0a:0:b0:3b6:2d6d:3546 with SMTP id x10-20020ac84a0a000000b003b62d6d3546mr53029151qtq.64.1674777174879; Thu, 26 Jan 2023 15:52:54 -0800 (PST) Received: from localhost ([64.18.11.71]) by smtp.gmail.com with ESMTPSA id pj4-20020a05620a1d8400b0070648cf78bdsm1845526qkn.54.2023.01.26.15.52.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 26 Jan 2023 15:52:54 -0800 (PST) Date: Thu, 26 Jan 2023 18:52:53 -0500 From: Kevin O'Connor To: David Woodhouse Cc: seabios , xen-devel , qemu-devel , paul Subject: Re: [SeaBIOS] [SeaBIOS PATCH] xen: require Xen info structure at 0x1000 to detect Xen Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Received-SPF: pass client-ip=2607:f8b0:4864:20::831; envelope-from=kevin@koconnor.net; helo=mail-qt1-x831.google.com X-Spam_score_int: 12 X-Spam_score: 1.2 X-Spam_bar: + X-Spam_report: (1.2 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_SBL_CSS=3.335, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Fri, Jan 20, 2023 at 11:33:19AM +0000, David Woodhouse wrote: > From: David Woodhouse > > When running under Xen, hvmloader places a table at 0x1000 with the e820 > information and BIOS tables. If this isn't present, SeaBIOS will > currently panic. > > We now have support for running Xen guests natively in QEMU/KVM, which > boots SeaBIOS directly instead of via hvmloader, and does not provide > the same structure. > > As it happens, this doesn't matter on first boot. because although we > set PlatformRunningOn to PF_QEMU|PF_XEN, reading it back again still > gives zero. Presumably because in true Xen, this is all already RAM. But > in QEMU with a faithfully-emulated PAM config in the host bridge, it's > still in ROM mode at this point so we don't see what we've just written. > > On reboot, however, the region *is* set to RAM mode and we do see the > updated value of PlatformRunningOn, do manage to remember that we've > detected Xen in CPUID, and hit the panic. > > It's not trivial to detect QEMU vs. real Xen at the time xen_preinit() > runs, because it's so early. We can't even make a XENVER_extraversion > hypercall to look for hints, because we haven't set up the hypercall > page (and don't have an allocator to give us a page in which to do so). > > So just make Xen detection contingent on the info structure being > present. If it wasn't, we were going to panic anyway. That leaves us > taking the standard QEMU init path for Xen guests in native QEMU, > which is just fine. > > Untested on actual Xen but ObviouslyCorrect™. Thanks. I don't have a way to test this, but it looks fine to me. I'll give a few more days to see if others have comments, and otherwise look to commit. Cheers, -Kevin