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 2CCFF23CB; Fri, 28 Mar 2025 17:26:25 +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=1743182787; cv=none; b=cFXFmpRttjnT7Wv8DFwa9iTtMxtPCQzMxZRBuoGVtaDC5Cdv/QBhgeMKwnVUQa6Fl09GxeVfZMbewGBnK5FizSQIjHNHniEEgsp2F4i4mc8IiO0eL05SnKwIvn/KKpliukouZeSXPdv1hgXYUZqUFU7sJCUJM4v2A4caaSjorOY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743182787; c=relaxed/simple; bh=NuLgCqHmnQ0wvILrKWLCFbD5y2KRQVi/PxqscccoZZs=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=j0iEtRL2NgPhIsKx7uDMvmWeqE++ZB7wRZVEIfb6fmQFKaNAYJEZRVo+wnAn2q5QxgJFGbiJe7XmM4WSwYxMf83PgKjLCKAV6I1Nwp04tOViIIU8R2CkHJ3lQeg6/X5/YffadcQv8h+BshSfGzb1PYbXlsi8If0oY3eWEhKFprE= 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=IQGhsRLv; 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="IQGhsRLv" Received: from [192.168.7.202] ([71.202.166.45]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 52SHPuMJ2035654 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Fri, 28 Mar 2025 10:25:56 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 52SHPuMJ2035654 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025032001; t=1743182758; bh=3Q3WizmAsVjpsON47KnbDqn8XHmFer42sXL5XTkOsnY=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=IQGhsRLv6QYNGoeHugz3a/SEvN0EW5nPtTHHtcDAZ7HqsVD2+sq5dVKv/eHHokQGI kQXWKqX9a7E2MAm+xCEKVAMKTZRURRICj63dCPJdE/IrMd898QHl5W5vkJX3v9+ckH BS2D24eFj+ld4P11z/u2q1UC/PGQSPd3ZhhO/tAA9RzDvGwu1e0iVlAMIm3WqJ099C jxuPdk4QKvVkXddLUBDHjyl5L2nNxjZ6Wgxn6x+Hkx9zfNAfuV2enoREbHk/jqxjLi tsMP6/GxWYmDOHg3GQjDVaKB5O35v1I+NnsgJsYJ9KPfuit6mOP0HFPaMXxYkS0V1u cXMdqoKbeYViw== Message-ID: Date: Fri, 28 Mar 2025 10:25:55 -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 v4 00/19] Enable FRED with KVM VMX From: Xin Li To: pbonzini@redhat.com, seanjc@google.com, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Cc: corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, andrew.cooper3@citrix.com, luto@kernel.org, peterz@infradead.org, chao.gao@intel.com, xin3.li@intel.com References: <20250328171205.2029296-1-xin@zytor.com> Content-Language: en-US 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: <20250328171205.2029296-1-xin@zytor.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/28/2025 10:11 AM, Xin Li (Intel) wrote: > This patch set enables the Intel flexible return and event delivery > (FRED) architecture with KVM VMX to allow guests to utilize FRED. > > The FRED architecture defines simple new transitions that change > privilege level (ring transitions). The FRED architecture was > designed with the following goals: > > 1) Improve overall performance and response time by replacing event > delivery through the interrupt descriptor table (IDT event > delivery) and event return by the IRET instruction with lower > latency transitions. > > 2) Improve software robustness by ensuring that event delivery > establishes the full supervisor context and that event return > establishes the full user context. > > The new transitions defined by the FRED architecture are FRED event > delivery and, for returning from events, two FRED return instructions. > FRED event delivery can effect a transition from ring 3 to ring 0, but > it is used also to deliver events incident to ring 0. One FRED > instruction (ERETU) effects a return from ring 0 to ring 3, while the > other (ERETS) returns while remaining in ring 0. Collectively, FRED > event delivery and the FRED return instructions are FRED transitions. > > Intel VMX architecture is extended to run FRED guests, and the major > changes are: > > 1) New VMCS fields for FRED context management, which includes two new > event data VMCS fields, eight new guest FRED context VMCS fields and > eight new host FRED context VMCS fields. > > 2) VMX nested-exception support for proper virtualization of stack > levels introduced with FRED architecture. > > Search for the latest FRED spec in most search engines with this search > pattern: > > site:intel.com FRED (flexible return and event delivery) specification > > Following is the link to the v3 of this patch set: > https://lore.kernel.org/lkml/20241001050110.3643764-1-xin@zytor.com/ > > Since several preparatory patches in v3 have been merged, and Sean > reiterated that it's NOT worth to precisely track which fields are/ > aren't supported [1], v4 patch number is reduced to 19. > > Although FRED and CET supervisor shadow stacks are independent CPU > features, FRED unconditionally includes FRED shadow stack pointer > MSRs IA32_FRED_SSP[0123], and IA32_FRED_SSP0 is just an alias of the > CET MSR IA32_PL0_SSP. IOW, the state management of MSR IA32_PL0_SSP > becomes an overlap area, and Sean requested that FRED virtualization > to land after CET virtualization [2]. Hi Sean, Any chance we could merge FRED ahead of CET? Ofc with proper changes to FRED code. Thanks! Xin > > [1]: https://lore.kernel.org/lkml/Z73uK5IzVoBej3mi@google.com/ > [2]: https://lore.kernel.org/kvm/ZvQaNRhrsSJTYji3@google.com/