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[170.10.133.124]) by mx.google.com with ESMTPS id f18-20020ac87f12000000b003b9ea6c2a95si7359955qtk.559.2023.03.06.01.27.08 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 06 Mar 2023 01:27:08 -0800 (PST) Received-SPF: pass (google.com: domain of berrange@redhat.com designates 170.10.133.124 as permitted sender) client-ip=170.10.133.124; Authentication-Results: mx.google.com; dkim=pass header.i=@redhat.com header.s=mimecast20190719 header.b="Y+f8n/eK"; spf=pass (google.com: domain of berrange@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=berrange@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1678094828; h=from:from:reply-to: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=RVCxoISPsMUUVKX9jBhQfLyhrTTxfK/FPc4RIMTqVfU=; b=Y+f8n/eKuL9lWAviCeZTJPyQhtfqIuW54uiDcfNCC/IdaaZPjT9/UmEZLEdiihXk+xZI05 52FZSThd8ZmZvAnfFCItH9kG0tTH266ijPg0kA7otKXHMHgRpPv1yq4JB3KhepXK43/8iz tG/jphKJyET3w6h492tsaRVsKhIz4oo= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-498-tuDuK4RnONuyfVEmCP4RgA-1; Mon, 06 Mar 2023 04:27:07 -0500 X-MC-Unique: tuDuK4RnONuyfVEmCP4RgA-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id CFFE1811E6E; Mon, 6 Mar 2023 09:27:06 +0000 (UTC) Received: from redhat.com (unknown [10.33.36.53]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 79A0140CF8F0; Mon, 6 Mar 2023 09:27:03 +0000 (UTC) Date: Mon, 6 Mar 2023 09:27:01 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Thomas Huth Cc: qemu-devel@nongnu.org, Peter Maydell , Paolo Bonzini , Markus Armbruster , Alex =?utf-8?Q?Benn=C3=A9e?= , qemu-arm@nongnu.org, Maxim Levitsky , libvir-list@redhat.com, Richard Henderson , xen-devel@lists.xenproject.org, Reinoud Zandijk , Wilfred Mallawa , John Paul Adrian Glaubitz Subject: Re: [PATCH v4 2/5] docs/about/deprecated: Deprecate the qemu-system-i386 binary Message-ID: Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20230306084658.29709-1-thuth@redhat.com> <20230306084658.29709-3-thuth@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230306084658.29709-3-thuth@redhat.com> User-Agent: Mutt/2.2.9 (2022-11-12) X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-TUID: lext43em7kz/ On Mon, Mar 06, 2023 at 09:46:55AM +0100, Thomas Huth wrote: > Aside from not supporting KVM on 32-bit hosts, the qemu-system-x86_64 > binary is a proper superset of the qemu-system-i386 binary. With the > 32-bit host support being deprecated, it is now also possible to > deprecate the qemu-system-i386 binary. > > With regards to 32-bit KVM support in the x86 Linux kernel, > the developers confirmed that they do not need a recent > qemu-system-i386 binary here: > > https://lore.kernel.org/kvm/Y%2ffkTs5ajFy0hP1U@google.com/ > > Reviewed-by: Daniel P. Berrangé > Reviewed-by: Wilfred Mallawa > Signed-off-by: Thomas Huth > --- > docs/about/deprecated.rst | 14 ++++++++++++++ > 1 file changed, 14 insertions(+) > > diff --git a/docs/about/deprecated.rst b/docs/about/deprecated.rst > index 1ca9dc33d6..c4fcc6b33c 100644 > --- a/docs/about/deprecated.rst > +++ b/docs/about/deprecated.rst > @@ -34,6 +34,20 @@ deprecating the build option and no longer defend it in CI. The > ``--enable-gcov`` build option remains for analysis test case > coverage. > > +``qemu-system-i386`` binary (since 8.0) > +''''''''''''''''''''''''''''''''''''''' > + > +The ``qemu-system-i386`` binary was mainly useful for running with KVM > +on 32-bit x86 hosts, but most Linux distributions already removed their > +support for 32-bit x86 kernels, so hardly anybody still needs this. The > +``qemu-system-x86_64`` binary is a proper superset and can be used to > +run 32-bit guests by selecting a 32-bit CPU model, including KVM support > +on x86_64 hosts. Thus users are recommended to reconfigure their systems > +to use the ``qemu-system-x86_64`` binary instead. If a 32-bit CPU guest > +environment should be enforced, you can switch off the "long mode" CPU > +flag, e.g. with ``-cpu max,lm=off``. I had the idea to check this today and this is not quite sufficient, because we have code that changes the family/model/stepping for 'max' which is target dependent: #ifdef TARGET_X86_64 object_property_set_int(OBJECT(cpu), "family", 15, &error_abort); object_property_set_int(OBJECT(cpu), "model", 107, &error_abort); object_property_set_int(OBJECT(cpu), "stepping", 1, &error_abort); #else object_property_set_int(OBJECT(cpu), "family", 6, &error_abort); object_property_set_int(OBJECT(cpu), "model", 6, &error_abort); object_property_set_int(OBJECT(cpu), "stepping", 3, &error_abort); #endif The former is a 64-bit AMD model and the latter is a 32-bit model. Seems LLVM was sensitive to this distinction to some extent: https://gitlab.com/qemu-project/qemu/-/issues/191 A further difference is that qemy-system-i686 does not appear to enable the 'syscall' flag, but I've not figured out where that difference is coming from in the code. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|