From nobody Fri Dec 19 12:32:33 2025 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 3749818FC6E for ; Tue, 9 Jul 2024 15:41:30 +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=1720539692; cv=none; b=uSc6AEPyNkFmXeyGgTnhentFbCP4vbwp2mZvOwKvld3SamlYu/HkaUVc7/dZLGhjZWb80z3raKYZ0UKwBpEHmM0WlAEkl4f7Iybca0zfObdFrXbDWaPv/q8VS7etJH7F74o2jO1/bUxG3YMeQNqazOkgg6BtkZZAquVBXDaQlL8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720539692; c=relaxed/simple; bh=oQ5rHh/qVIUVk3bU5g69AR53OwoI0yLAz7n/fyMP8ZQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=e36v2XQ+5KSzSphFOVKZRiP3fV/And9R5hFNoiadM+5MdHkSMiBAjp4uaAjNy5T1mUSem8qw3ncbcJY21fFqATocVYd7fls4F2hTRTTxb6VaKVN4H/yTd4mRswP1aOQoSOU81V//EIakRL8FGPVB4yZ96L5UEH63xUCZOo1dxWs= 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=Tpg1ZNep; 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="Tpg1ZNep" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 469FemH13543378 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 9 Jul 2024 08:41:01 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 469FemH13543378 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024061501; t=1720539661; bh=pR4B9H85x4ggNeQfQfQV1EF3QFKnnueIe5cRPRm/ZjQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Tpg1ZNepji5w0QuBNN367hst5fztm0wW2xQF0Cq63MI9t2DpK3HyDobP8i4/tdz2+ kyVpY5jcCKDp03r0ZgCgmW9GsJZ2zq91p34A9ks4V7LARVGgd65wsy+TQWWw6gXilF H6zozDHq6/eTt4vnjlKgJBQhir66InfEv1GU0uNzedSaioJxW1OOGmTkcvHruMuBab 3dwkuwAubSGPtbORsxS+SIIydBpRno7wl7qpP/hDla6QI8YsdIhM7vSFbr355iFCEJ evxxajpi51N6kNsIfycFxCezhEZNXoQQ9202p8vnVlr0oJllLnBXJf9rB97CyEvMRZ R3OrvwKgaaNFQ== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, nik.borisov@suse.com, houwenlong.hwl@antgroup.com Subject: [PATCH v2 1/3] x86/fred: Parse cmdline param "fred=" in cpu_parse_early_param() Date: Tue, 9 Jul 2024 08:40:46 -0700 Message-ID: <20240709154048.3543361-2-xin@zytor.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240709154048.3543361-1-xin@zytor.com> References: <20240709154048.3543361-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Depending on whether FRED will be used, sysvec_install() installs a system interrupt handler into FRED system vector dispatch table or IDT. However FRED can be disabled later in trap_init(), after sysvec_install() is called. E.g., the HYPERVISOR_CALLBACK_VECTOR handler is registered with sysvec_install() in kvm_guest_init(), which is called in setup_arch() but way before trap_init(). IOW, there is a gap between FRED is available and available but disabled. As a result, when FRED is available but disabled, its IDT handler is not installed thus spurious_interrupt() will be invoked. Fix it by parsing cmdline param "fred=3D" in cpu_parse_early_param() to minimize the gap between FRED is available and available but disabled. Fixes: 3810da12710a ("x86/fred: Add a fred=3D cmdline param") Reported-by: Hou Wenlong Suggested-by: Thomas Gleixner Signed-off-by: Xin Li (Intel) --- Change since v1: * Use strncmp() instead of strcmp(). --- arch/x86/kernel/cpu/common.c | 5 +++++ arch/x86/kernel/traps.c | 26 -------------------------- 2 files changed, 5 insertions(+), 26 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d4e539d4e158..10a5402d8297 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1510,6 +1510,11 @@ static void __init cpu_parse_early_param(void) if (cmdline_find_option_bool(boot_command_line, "nousershstk")) setup_clear_cpu_cap(X86_FEATURE_USER_SHSTK); =20 + /* Minimize the gap between FRED is available and available but disabled.= */ + arglen =3D cmdline_find_option(boot_command_line, "fred", arg, sizeof(arg= )); + if (arglen !=3D 2 || strncmp(arg, "on", 2)) + setup_clear_cpu_cap(X86_FEATURE_FRED); + arglen =3D cmdline_find_option(boot_command_line, "clearcpuid", arg, size= of(arg)); if (arglen <=3D 0) return; diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 4fa0b17e5043..6afb41e6cbbb 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -1402,34 +1402,8 @@ DEFINE_IDTENTRY_SW(iret_error) } #endif =20 -/* Do not enable FRED by default yet. */ -static bool enable_fred __ro_after_init =3D false; - -#ifdef CONFIG_X86_FRED -static int __init fred_setup(char *str) -{ - if (!str) - return -EINVAL; - - if (!cpu_feature_enabled(X86_FEATURE_FRED)) - return 0; - - if (!strcmp(str, "on")) - enable_fred =3D true; - else if (!strcmp(str, "off")) - enable_fred =3D false; - else - pr_warn("invalid FRED option: 'fred=3D%s'\n", str); - return 0; -} -early_param("fred", fred_setup); -#endif - void __init trap_init(void) { - if (cpu_feature_enabled(X86_FEATURE_FRED) && !enable_fred) - setup_clear_cpu_cap(X86_FEATURE_FRED); - /* Init cpu_entry_area before IST entries are set up */ setup_cpu_entry_areas(); =20 --=20 2.45.2 From nobody Fri Dec 19 12:32:33 2025 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 6B1F319CD0C for ; 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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="B0v0cL+h" Received: from terminus.zytor.com (terminus.zytor.com [IPv6:2607:7c80:54:3:0:0:0:136]) (authenticated bits=0) by mail.zytor.com (8.17.2/8.17.1) with ESMTPSA id 469FemH23543378 (version=TLSv1.3 cipher=TLS_AES_256_GCM_SHA384 bits=256 verify=NO); Tue, 9 Jul 2024 08:41:01 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 469FemH23543378 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024061501; t=1720539662; bh=Y3T6o5mCEOAL/OthkgfETflzFrViYS0KVTQMPve51XI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=B0v0cL+hvAQnD4zPUvLZ98YLKgNf1DZ8n2VRW+LfuqQRALzztYh+Jb8yfTZ90m9Wu b9VGGcGLNUzxM4zRMt0S0WPBouDNxR0TEEvSEf8BNSGiEK3kAlimAwCYb8QzF0ub94 jJkLsQ8hubfHDNWeLrLF2pMyJ4MpOgIHzMRd2t2cZjnw+kr9w6/BEsCVj/rd7p0sKz B/i0avsNezrE87vQ6X23k8sB3bog+9nbsqzamQ5UgK+UvgEqG0AM0XRxmnQEvgLc1K U9+D97YeXzwOmW5l/S9t3vjOPatseA8+evQHDLcpeLJKoS8GB22ynUuFE9oYcg7dqV szWetbbgjpbyA== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, nik.borisov@suse.com, houwenlong.hwl@antgroup.com Subject: [PATCH v2 2/3] x86/fred: Split FRED RSP initialization into a separate function Date: Tue, 9 Jul 2024 08:40:47 -0700 Message-ID: <20240709154048.3543361-3-xin@zytor.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240709154048.3543361-1-xin@zytor.com> References: <20240709154048.3543361-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" To enable FRED earlier, split FRED RSP initialization into a separate function, as they are initialized with memory from CPU entry areas, thus their initialization has to be kept after setup_cpu_entry_areas(). No functional change intended. Signed-off-by: Xin Li (Intel) --- arch/x86/include/asm/fred.h | 2 ++ arch/x86/kernel/cpu/common.c | 6 ++++-- arch/x86/kernel/fred.c | 28 +++++++++++++++++++--------- 3 files changed, 25 insertions(+), 11 deletions(-) diff --git a/arch/x86/include/asm/fred.h b/arch/x86/include/asm/fred.h index e86c7ba32435..66d7dbe2d314 100644 --- a/arch/x86/include/asm/fred.h +++ b/arch/x86/include/asm/fred.h @@ -84,11 +84,13 @@ static __always_inline void fred_entry_from_kvm(unsigne= d int type, unsigned int } =20 void cpu_init_fred_exceptions(void); +void cpu_init_fred_rsps(void); void fred_complete_exception_setup(void); =20 #else /* CONFIG_X86_FRED */ static __always_inline unsigned long fred_event_data(struct pt_regs *regs)= { return 0; } static inline void cpu_init_fred_exceptions(void) { } +static inline void cpu_init_fred_rsps(void) { } static inline void fred_complete_exception_setup(void) { } static __always_inline void fred_entry_from_kvm(unsigned int type, unsigne= d int vector) { } #endif /* CONFIG_X86_FRED */ diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 10a5402d8297..6de12b3c1b04 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2195,10 +2195,12 @@ void cpu_init_exception_handling(void) /* GHCB needs to be setup to handle #VC. */ setup_ghcb(); =20 - if (cpu_feature_enabled(X86_FEATURE_FRED)) + if (cpu_feature_enabled(X86_FEATURE_FRED)) { cpu_init_fred_exceptions(); - else + cpu_init_fred_rsps(); + } else { load_current_idt(); + } } =20 /* diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c index 4bcd8791ad96..99a134fcd5bf 100644 --- a/arch/x86/kernel/fred.c +++ b/arch/x86/kernel/fred.c @@ -32,6 +32,25 @@ void cpu_init_fred_exceptions(void) FRED_CONFIG_INT_STKLVL(0) | FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); =20 + wrmsrl(MSR_IA32_FRED_STKLVLS, 0); + wrmsrl(MSR_IA32_FRED_RSP0, 0); + wrmsrl(MSR_IA32_FRED_RSP1, 0); + wrmsrl(MSR_IA32_FRED_RSP2, 0); + wrmsrl(MSR_IA32_FRED_RSP3, 0); + + /* Enable FRED */ + cr4_set_bits(X86_CR4_FRED); + /* Any further IDT use is a bug */ + idt_invalidate(); + + /* Use int $0x80 for 32-bit system calls in FRED mode */ + setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); + setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); +} + +/* Must be called after setup_cpu_entry_areas() */ +void cpu_init_fred_rsps(void) +{ /* * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* * (remember that user space faults are always taken on stack level 0) @@ -47,13 +66,4 @@ void cpu_init_fred_exceptions(void) wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); - - /* Enable FRED */ - cr4_set_bits(X86_CR4_FRED); - /* Any further IDT use is a bug */ - idt_invalidate(); - - /* Use int $0x80 for 32-bit system calls in FRED mode */ - setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); - setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); } --=20 2.45.2 From nobody Fri Dec 19 12:32:33 2025 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 3777119D8A4 for ; Tue, 9 Jul 2024 15:41:33 +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=1720539695; cv=none; b=hNXTdBi9WNZa6F53CPu3kiVh2I3zSqrLJK7F5lJ3JQq6/cD03wCe2sQrRzQpENGjUZZGkcvI+suqpNnDRh3ZudH2JiXlEt7+mep12swvuFmBcypdzdlp7Sw5NfTgMgVYRUbs20s5u47IepNmvZwPpdnjBqiEu3KggerKYYgvqi4= ARC-Message-Signature: i=1; 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Tue, 9 Jul 2024 08:41:02 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 469FemH33543378 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2024061501; t=1720539663; bh=qfun97Jg+BIQEJ3LYgyV2vxqbqRdLnKMxvQ2b7HT42I=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TKKM5aCs0rovstLABu+Hh7Y4R9pFBlfuWr7lfH4ZYBDA8YESDYVjdPXO89ne0bMP6 koyDpyIbjmDsYyHxOAJHJv886LbfK4QWcrnL7ezBSZ1QzbWrOxTlfd76mu1jzLvbsY C/qUIhdxjPjIjZA+pLqsv9c+eAc04xWY5V2GN/J1gNDLuIvzlpZq6Kx5N/DQaXAqDi sIGdlnBL5ZA5OF9d9slUqH6xqObxaMXsdyJCsnQlZj5YFEhwVqQcubn422zhWG9Osy gUk5G0UF5+oGgMndoAXAKbJBR9k6rRG/r9GuUn2foMnN2qlC92nkd/EEoxawJU9+r9 gu3uUdHe21rGg== From: "Xin Li (Intel)" To: linux-kernel@vger.kernel.org Cc: hpa@zytor.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, nik.borisov@suse.com, houwenlong.hwl@antgroup.com Subject: [PATCH v2 3/3] x86/fred: Enable FRED right after init_mem_mapping() Date: Tue, 9 Jul 2024 08:40:48 -0700 Message-ID: <20240709154048.3543361-4-xin@zytor.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240709154048.3543361-1-xin@zytor.com> References: <20240709154048.3543361-1-xin@zytor.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Enable FRED right after init_mem_mapping() to avoid #PF handler, exc_page_fault(), fetching its faulting address from the stack before FRED is enabled. Fixes: 14619d912b65 ("x86/fred: FRED entry/exit and dispatch code") Reported-by: Hou Wenlong Suggested-by: Thomas Gleixner Signed-off-by: Xin Li (Intel) --- arch/x86/kernel/cpu/common.c | 6 +----- arch/x86/kernel/setup.c | 11 ++++++++++- arch/x86/kernel/smpboot.c | 6 ++++++ arch/x86/kernel/traps.c | 4 ++++ 4 files changed, 21 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 6de12b3c1b04..42d4136ed6ac 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -2195,12 +2195,8 @@ void cpu_init_exception_handling(void) /* GHCB needs to be setup to handle #VC. */ setup_ghcb(); =20 - if (cpu_feature_enabled(X86_FEATURE_FRED)) { - cpu_init_fred_exceptions(); - cpu_init_fred_rsps(); - } else { + if (!cpu_feature_enabled(X86_FEATURE_FRED)) load_current_idt(); - } } =20 /* diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c index 728927e4ba51..36403b901eb2 100644 --- a/arch/x86/kernel/setup.c +++ b/arch/x86/kernel/setup.c @@ -39,6 +39,7 @@ #include #include #include +#include #include #include #include @@ -1040,7 +1041,15 @@ void __init setup_arch(char **cmdline_p) =20 init_mem_mapping(); =20 - idt_setup_early_pf(); + /* + * init_mem_mapping() uses early IDT to setup memory mappings, thus FRED + * can't be enabled earlier than that, unless FRED adds support to setup + * memory mappings. + */ + if (cpu_feature_enabled(X86_FEATURE_FRED)) + cpu_init_fred_exceptions(); + else + idt_setup_early_pf(); =20 /* * Update mmu_cr4_features (and, indirectly, trampoline_cr4_features) diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c index 0c35207320cb..0d83377f9dcd 100644 --- a/arch/x86/kernel/smpboot.c +++ b/arch/x86/kernel/smpboot.c @@ -64,6 +64,7 @@ #include #include #include +#include #include #include #include @@ -248,6 +249,11 @@ static void notrace start_secondary(void *unused) =20 cpu_init_exception_handling(); =20 + if (cpu_feature_enabled(X86_FEATURE_FRED)) { + cpu_init_fred_exceptions(); + cpu_init_fred_rsps(); + } + /* * Load the microcode before reaching the AP alive synchronization * point below so it is not part of the full per CPU serialized diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 6afb41e6cbbb..81648bd07576 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -1407,6 +1407,10 @@ void __init trap_init(void) /* Init cpu_entry_area before IST entries are set up */ setup_cpu_entry_areas(); =20 + /* FRED RSPs pointing to memory from CPU entry areas */ + if (cpu_feature_enabled(X86_FEATURE_FRED)) + cpu_init_fred_rsps(); + /* Init GHCB memory pages when running as an SEV-ES guest */ sev_es_init_vc_handling(); =20 --=20 2.45.2