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 814792FF673; Tue, 14 Oct 2025 01:11:14 +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=1760404276; cv=none; b=Tsw9rc6GAHxIXItGTHCeTA6RZGFPe2XqwdeVyDmHPSv7Jqk6sny9yayjq4hvMj85y6Q839HFZhDdO6SQOghh6tQ2ID8v2kbS5CqRuZvzhH59XcK5dS7W/t4kdg/zHMmtfEaaC2O08P7lFJ3LfevwwOC8VO+FAbWnoGXWgqsU0Uw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760404276; c=relaxed/simple; bh=VpNU3uAT7mWuJwH8wgjR94vYaC45sWLYg4ZUqnCR7PM=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=lyiS9OcP1RuRtr9L50XrBSzdmW8U0utJKL/CQ9KU10AFBAigRmOk0TG2S6jCU68SxYKwEDPxRJoAeIlxKBSciGOmE0SGtmiqNrpjnAiqb6+n+rOXB7zQfGpJjVHuklx+7kTmGYvAyuW5S2FUaUnynej45npAaylRa0h+TYvePkE= 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=RT+sRZVm; 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="RT+sRZVm" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 59E19p1N1568441 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Mon, 13 Oct 2025 18:09:54 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 59E19p1N1568441 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025092201; t=1760404195; bh=DhpU952qtckeUC/UYfgDcfu0CINppd+EV+oQjg57wY8=; h=From:To:Cc:Subject:Date:From; b=RT+sRZVmH82cHCtH+K6G+meVF8PtkV432FDEWprM4vWg8G5Lx57oK4ztX5xFsNNjM YtVi2yzo+9VoJMX4w/mzm83U7lQ5YbEsgffzXZjUFotTX+ohlELeYYIiyyAXn2dn2n R8ehrmmDd5biBXODAphoEobksgfdh5/CTIck6/2ptRods48oxhYAsBRumBjjYYzNf5 +kVFBs26i2M79G4NlkoJgNS/0ehZGMS6d/OUydrAQqePjmYhttMs9+gNyZgmrQwtPa KlKd/XQ8nLyrGUV1aGCMdb7CrRkkXLGsh4B+/Cp1SB7NLpIpy8wN5eYY26z0WKAbfA yOUVWxuoSB4lw== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org Cc: pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, xin@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org Subject: [PATCH v8 00/21] Enable FRED with KVM VMX Date: Mon, 13 Oct 2025 18:09:29 -0700 Message-ID: <20251014010950.1568389-1-xin@zytor.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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 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 [1]. Since CET virtualization has landed with the release of v6.18-rc1, I'm submitting v8 of FRED virtualization. Changes in v8: * Rebased on v6.18-rc1. * Relocate secondary_vm_exit_controls to the last u64 padding field in vmcs12 (Isaku). * Make the newly added FRED fields 64-bit aligned in vmcs12 (Isaku). * Remove changes to Documentation/virt/kvm/x86/nested-vmx.rst. * Update KVM_CAP_EXCEPTION_NESTED_FLAG, as the number used in v7 is occupied by another new cap. Following is the link to v7 of this patch set: https://lore.kernel.org/lkml/20250829153149.2871901-1-xin@zytor.com/ [1]: https://lore.kernel.org/kvm/ZvQaNRhrsSJTYji3@google.com/ Xin Li (18): KVM: VMX: Add support for the secondary VM exit controls KVM: VMX: Initialize VM entry/exit FRED controls in vmcs_config KVM: VMX: Disable FRED if FRED consistency checks fail KVM: VMX: Initialize VMCS FRED fields KVM: VMX: Set FRED MSR intercepts KVM: VMX: Save/restore guest FRED RSP0 KVM: VMX: Add support for saving and restoring FRED MSRs KVM: x86: Add a helper to detect if FRED is enabled for a vCPU KVM: VMX: Virtualize FRED event_data KVM: VMX: Virtualize FRED nested exception tracking KVM: x86: Mark CR4.FRED as not reserved KVM: VMX: Dump FRED context in dump_vmcs() KVM: x86: Advertise support for FRED KVM: nVMX: Add support for the secondary VM exit controls KVM: nVMX: Add FRED VMCS fields to nested VMX context handling KVM: nVMX: Add FRED-related VMCS field checks KVM: nVMX: Add prerequisites to SHADOW_FIELD_R[OW] macros KVM: nVMX: Allow VMX FRED controls Xin Li (Intel) (3): x86/cea: Prefix event stack names with ESTACK_ x86/cea: Export API for per-CPU exception stacks for KVM KVM: x86: Save/restore the nested flag of an exception Documentation/virt/kvm/api.rst | 21 +- arch/x86/coco/sev/noinstr.c | 4 +- arch/x86/coco/sev/vc-handle.c | 2 +- arch/x86/include/asm/cpu_entry_area.h | 75 +++--- arch/x86/include/asm/kvm_host.h | 13 +- arch/x86/include/asm/msr-index.h | 1 + arch/x86/include/asm/vmx.h | 48 +++- arch/x86/include/uapi/asm/kvm.h | 4 +- arch/x86/kernel/cpu/common.c | 10 +- arch/x86/kernel/dumpstack_64.c | 14 +- arch/x86/kernel/fred.c | 6 +- arch/x86/kernel/traps.c | 2 +- arch/x86/kvm/cpuid.c | 1 + arch/x86/kvm/kvm_cache_regs.h | 15 ++ arch/x86/kvm/svm/svm.c | 2 +- arch/x86/kvm/vmx/capabilities.h | 25 +- arch/x86/kvm/vmx/nested.c | 338 ++++++++++++++++++++++---- arch/x86/kvm/vmx/nested.h | 22 ++ arch/x86/kvm/vmx/vmcs.h | 1 + arch/x86/kvm/vmx/vmcs12.c | 19 ++ arch/x86/kvm/vmx/vmcs12.h | 40 ++- arch/x86/kvm/vmx/vmcs_shadow_fields.h | 37 ++- arch/x86/kvm/vmx/vmx.c | 247 +++++++++++++++++-- arch/x86/kvm/vmx/vmx.h | 54 +++- arch/x86/kvm/x86.c | 131 +++++++++- arch/x86/kvm/x86.h | 8 +- arch/x86/mm/cpu_entry_area.c | 37 ++- arch/x86/mm/fault.c | 2 +- include/uapi/linux/kvm.h | 1 + 29 files changed, 1036 insertions(+), 144 deletions(-) base-commit: 3a8660878839faadb4f1a6dd72c3179c1df56787 -- 2.51.0