From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1A13763E for ; Sat, 22 Jun 2024 00:32:22 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719016344; cv=none; b=IxmI1kJHCXm1iChk5fDBNw9uy7bjRcL0OZeelt1k5FXZRlfkwurUovhz63kEEQyA1pqDsHeUInf6/WawM9h8uaw+B29i0m48vw4o5Ij1hMm0uhyhxiGbvm575J2L+2IGMdVtVzp2H6oMIPgDLd8e+9N45EBlUwQoAhVLkP+PV1w= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1719016344; c=relaxed/simple; bh=24/di/nQEB80I+4mmVpG4wYUtwjFONBgqLcDMtWGie0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=gjUYhZJxzbhMcVK9I/VKwRC/OtgA6hOA4sIpHElSYVmCMKaVD2wzqCxoMtgrqqiSqrwOoO1W+vfI/LZwSGHsc9B+5pG2rvsrgStV0GqNA1sZiTBgvASQIy0DTQxuaG5nZkYoIbMF9laB9MA/b3jc8YZl6ujgI0Bg7lnRgj1S/Bg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=nJhUUIL2; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="nJhUUIL2" Received: from [192.168.7.205] ([71.202.166.45]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 45M0VQAF3462277 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 21 Jun 2024 17:31:27 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 45M0VQAF3462277 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024061501; t=1719016289; bh=z+z8Oe9/SZ+Fl9R7KW8seIScjfZQWA1FIQve8M4KgBY=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=nJhUUIL2NVCGZDwb2MRwBG9QztxI5Wd9p6Lb+omb6dd6sY8ehZQa0Gfql/q7Oe2FY FPft7XLl5/XSS50HEZCIIqXf82wlMnBURAR2wFgSjFqUjM5/wn8eQ0Yv0KFP993AFH kYfLgPo737dG8fwXq0XyJYLh5jIoQw/nGEHkElr+ymp4pzq5/G5talDGquypbfQFam lGdqAGjzQZyEfRraGGAYnPYecfqMov7gy72hXitQbsaP4pLdfNNUItxGWGNVpscYvJ k04KX1NXW/3eWg24nq5xRS8OuEVEgNvHuiZorRyDK1bhvyGhMwmqBNxZwkFaczcM3D N/TRrTFkt61hw== Message-ID: <58ec98bf-b66c-4249-8a10-ff254cd405c2@zytor.com> Date: Fri, 21 Jun 2024 17:31:26 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 0/2] x86/fred: Fix two problems during the FRED initialization To: Hou Wenlong , linux-kernel@vger.kernel.org Cc: Lai Jiangshan , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Xin Li , Jacob Pan , Rick Edgecombe , Paolo Bonzini References: Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; keydata= xsDNBGUPz1cBDACS/9yOJGojBFPxFt0OfTWuMl0uSgpwk37uRrFPTTLw4BaxhlFL0bjs6q+0 2OfG34R+a0ZCuj5c9vggUMoOLdDyA7yPVAJU0OX6lqpg6z/kyQg3t4jvajG6aCgwSDx5Kzg5 Rj3AXl8k2wb0jdqRB4RvaOPFiHNGgXCs5Pkux/qr0laeFIpzMKMootGa4kfURgPhRzUaM1vy bsMsL8vpJtGUmitrSqe5dVNBH00whLtPFM7IbzKURPUOkRRiusFAsw0a1ztCgoFczq6VfAVu raTye0L/VXwZd+aGi401V2tLsAHxxckRi9p3mc0jExPc60joK+aZPy6amwSCy5kAJ/AboYtY VmKIGKx1yx8POy6m+1lZ8C0q9b8eJ8kWPAR78PgT37FQWKYS1uAroG2wLdK7FiIEpPhCD+zH wlslo2ETbdKjrLIPNehQCOWrT32k8vFNEMLP5G/mmjfNj5sEf3IOKgMTMVl9AFjsINLHcxEQ 6T8nGbX/n3msP6A36FDfdSEAEQEAAc0WWGluIExpIDx4aW5Aenl0b3IuY29tPsLBDQQTAQgA NxYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89XBQkFo5qAAhsDBAsJCAcFFQgJCgsFFgID AQAACgkQa70OVx2uN1HUpgv/cM2fsFCQodLArMTX5nt9yqAWgA5t1srri6EgS8W3F+3Kitge tYTBKu6j5BXuXaX3vyfCm+zajDJN77JHuYnpcKKr13VcZi1Swv6Jx1u0II8DOmoDYLb1Q2ZW v83W55fOWJ2g72x/UjVJBQ0sVjAngazU3ckc0TeNQlkcpSVGa/qBIHLfZraWtdrNAQT4A1fa sWGuJrChBFhtKbYXbUCu9AoYmmbQnsx2EWoJy3h7OjtfFapJbPZql+no5AJ3Mk9eE5oWyLH+ QWqtOeJM7kKvn/dBudokFSNhDUw06e7EoVPSJyUIMbYtUO7g2+Atu44G/EPP0yV0J4lRO6EA wYRXff7+I1jIWEHpj5EFVYO6SmBg7zF2illHEW31JAPtdDLDHYcZDfS41caEKOQIPsdzQkaQ oW2hchcjcMPAfyhhRzUpVHLPxLCetP8vrVhTvnaZUo0xaVYb3+wjP+D5j/3+hwblu2agPsaE vgVbZ8Fx3TUxUPCAdr/p73DGg57oHjgezsDNBGUPz1gBDAD4Mg7hMFRQqlzotcNSxatlAQNL MadLfUTFz8wUUa21LPLrHBkUwm8RujehJrzcVbPYwPXIO0uyL/F///CogMNx7Iwo6by43KOy g89wVFhyy237EY76j1lVfLzcMYmjBoTH95fJC/lVb5Whxil6KjSN/R/y3jfG1dPXfwAuZ/4N cMoOslWkfZKJeEut5aZTRepKKF54T5r49H9F7OFLyxrC/uI9UDttWqMxcWyCkHh0v1Di8176 jjYRNTrGEfYfGxSp+3jYL3PoNceIMkqM9haXjjGl0W1B4BidK1LVYBNov0rTEzyr0a1riUrp Qk+6z/LHxCM9lFFXnqH7KWeToTOPQebD2B/Ah5CZlft41i8L6LOF/LCuDBuYlu/fI2nuCc8d m4wwtkou1Y/kIwbEsE/6RQwRXUZhzO6llfoN96Fczr/RwvPIK5SVMixqWq4QGFAyK0m/1ap4 bhIRrdCLVQcgU4glo17vqfEaRcTW5SgX+pGs4KIPPBE5J/ABD6pBnUUAEQEAAcLA/AQYAQgA JhYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89ZBQkFo5qAAhsMAAoJEGu9DlcdrjdR4C0L /RcjolEjoZW8VsyxWtXazQPnaRvzZ4vhmGOsCPr2BPtMlSwDzTlri8BBG1/3t/DNK4JLuwEj OAIE3fkkm+UG4Kjud6aNeraDI52DRVCSx6xff3bjmJsJJMb12mWglN6LjdF6K+PE+OTJUh2F dOhslN5C2kgl0dvUuevwMgQF3IljLmi/6APKYJHjkJpu1E6luZec/lRbetHuNFtbh3xgFIJx 2RpgVDP4xB3f8r0I+y6ua+p7fgOjDLyoFjubRGed0Be45JJQEn7A3CSb6Xu7NYobnxfkwAGZ Q81a2XtvNS7Aj6NWVoOQB5KbM4yosO5+Me1V1SkX2jlnn26JPEvbV3KRFcwV5RnDxm4OQTSk PYbAkjBbm+tuJ/Sm+5Yp5T/BnKz21FoCS8uvTiziHj2H7Cuekn6F8EYhegONm+RVg3vikOpn gao85i4HwQTK9/D1wgJIQkdwWXVMZ6q/OALaBp82vQ2U9sjTyFXgDjglgh00VRAHP7u1Rcu4 l75w1xInsg== In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 6/21/2024 6:12 AM, Hou Wenlong wrote: > When I reviewed the FRED code and attempted to implement a FRED-like > event delivery for my PV guest, I encountered two problems which I may > have misunderstood. Hi Wenlong, Thanks for bringing the issues up. > > One issue is that FRED can be disabled in trap_init(), but > sysvec_install() can be called before trap_init(), thus the system > interrupt handler is not installed into the IDT if FRED is disabled > later. Initially, I attempted to parse the cmdline and decide whether to > enable or disable FRED after parse_early_param(). However, I ultimately > chose to always install the system handler into the IDT in > sysvec_install(), which is simple and should be sufficient. Which module with a system vector gets initialized before trap_init() is called? > Another problem is that the page fault handler (exc_page_fault()) is > installed into the IDT before FRED is enabled. Consequently, if a #PF is > triggered in this gap, the handler would receive the wrong CR2 from the > stack if FRED feature is present. To address this, I added a page fault > entry stub for FRED similar to the debug entry. However, I'm uncertain > whether this is enough reason to add a new entry. Perhaps a static key > may suffice to indicate whether FRED setup is completed and the handler > can use it. How could a #PF get triggered during that gap? Initialization time funnies are really unpleasant. Thanks! Xin