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[54.240.197.239]) by smtp.gmail.com with ESMTPSA id iz17-20020a05600c555100b003db07420d14sm2065074wmb.39.2023.01.26.09.49.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 26 Jan 2023 09:49:23 -0800 (PST) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: c575218e-9da1-11ed-a5d9-ddcf98b90cbd DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:organization:content-language :references:to:subject:reply-to:user-agent:mime-version:date :message-id:from:from:to:cc:subject:date:message-id:reply-to; bh=OK8D8R+tAQUoFtCWzoU1n8SQdUbAKXNoKJvtArjQYWo=; b=fsrSpnrqMY978vETifGGB5jJhFgGa9z1kwcWK6T2nOCu+2w+3q003EfrS2S3nto/9O lxe3tYcU8G4mfiFeNDwyeOtZ6IpN6OGNe5mvX2oCYaolr2h2fKwfDb+bxz95DcEGZcgt baW9SuyDs+IEAs4Fczqco/bSDXCuXJ9zw8fBxPmw1fsMHyYS/OnDg/d4M0REeUbUPJvJ RQv6LwyWhdbAqU2ztQFsLdrlFMGtDLdvlO64WYfr1H45JdhGSnTHa0NWmRYX1GMcLOq5 lgctRAthj0M2xFVSiOFnZZWIfgJNNw6o+vkIeVJ+9yWcTvOSRYMwMeFWYUlgDljKCXEG ExkA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:organization:content-language :references:to:subject:reply-to:user-agent:mime-version:date :message-id:from:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=OK8D8R+tAQUoFtCWzoU1n8SQdUbAKXNoKJvtArjQYWo=; b=tYpBlRY33xSJenDPb3hlqVO868Xecr7i7h0mMR0sPv4esnzAfEZE4bDq2wka3SvRNA tXAPRfavCTcFUenLb8Xe7Bnxi4Vp3wp7zGVzb6qmqCjd7/ew3Ne90m23dr/GyiebSWIw rRJ6cjkDpf6Z/ct+XyaqGYzRoZLYJvuEKjR8uZaV6w2O405ytmBzcG/Rua2oS+FTHJmi AA0BRHQ0UG0GpMtDdAkYzOHFPLWHQ7NshrIIxIRV7CkZlIQnZZsHjw6hyINyr0jQ7cgc 5Z22hpgL6Y69IJEeWmyynbjF/HDUuji++f7I8pUi62EFHhD1dXd0qb14IE6KuBtKGrQk Wvgw== X-Gm-Message-State: AFqh2kpD0EDjORh43OdWZ49kouQ9Z2bwyFH5NeCYH9lIhQv2lc3oaG8a ir5IEH8OOoxsToJA0z3tXKU= X-Google-Smtp-Source: AMrXdXs5F4OCgvN3uEJ60IUaqKqHzXV14E3jUKorb3s+0tE+r6nmGLv0K7Ivj0ZpjpxRkHHOTPAUPQ== X-Received: by 2002:a05:600c:3ac8:b0:3da:270b:ba6b with SMTP id d8-20020a05600c3ac800b003da270bba6bmr37704210wms.41.1674755364280; Thu, 26 Jan 2023 09:49:24 -0800 (PST) From: Paul Durrant X-Google-Original-From: Paul Durrant Message-ID: <46ea1f4e-2061-d5f8-2b44-5d24a3a3e7ca@xen.org> Date: Thu, 26 Jan 2023 17:49:22 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.6.1 Reply-To: paul@xen.org Subject: Re: [SeaBIOS PATCH] xen: require Xen info structure at 0x1000 to detect Xen To: David Woodhouse , seabios , xen-devel , qemu-devel References: Content-Language: en-US Organization: Xen Project In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 20/01/2023 11:33, 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™. Works for me... Tested-by: Paul Durrant > > Signed-off-by: David Woodhouse > --- > src/fw/xen.c | 45 ++++++++++++++++++++++++++++++++------------- > 1 file changed, 32 insertions(+), 13 deletions(-) > Also... Reviewed-by: Paul Durrant