From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 420A6C47089 for ; Thu, 27 May 2021 00:29:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 16AB3613AC for ; Thu, 27 May 2021 00:29:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234435AbhE0AbT (ORCPT ); Wed, 26 May 2021 20:31:19 -0400 Received: from mga12.intel.com ([192.55.52.136]:58472 "EHLO mga12.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232903AbhE0AbS (ORCPT ); Wed, 26 May 2021 20:31:18 -0400 IronPort-SDR: GSuDlhoBJQsgcYbPuCGjOLOOUiAOBbCgU538MHSEu5y5tQhxnPEunrURHrAzXMXx+YdLBvwNn+ EKX6v+HIe9Sg== X-IronPort-AV: E=McAfee;i="6200,9189,9996"; a="182268461" X-IronPort-AV: E=Sophos;i="5.82,333,1613462400"; d="scan'208";a="182268461" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 May 2021 17:29:44 -0700 IronPort-SDR: Thi5SwBK4GdZlu5ZZDXBBc2rUKJWyQNH+Yc9d5c2PJMub14o1vNSYPiIrcsT8H57W0rukluIGN MstgWn6nc8RQ== X-IronPort-AV: E=Sophos;i="5.82,333,1613462400"; d="scan'208";a="480331177" Received: from skgangad-mobl.amr.corp.intel.com (HELO skuppusw-desk1.amr.corp.intel.com) ([10.254.33.45]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 May 2021 17:29:43 -0700 From: Kuppuswamy Sathyanarayanan To: Peter Zijlstra , Andy Lutomirski , Dave Hansen , Tony Luck Cc: Andi Kleen , Kirill Shutemov , Kuppuswamy Sathyanarayanan , Dan Williams , Raj Ashok , Sean Christopherson , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org Subject: [RFC v2-fix-v2 1/1] x86/traps: Add #VE support for TDX guest Date: Wed, 26 May 2021 17:29:31 -0700 Message-Id: <20210527002931.3632581-1-sathyanarayanan.kuppuswamy@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <4031ffc2-a442-5da7-e793-ac1053533bb3@linux.intel.com> References: <4031ffc2-a442-5da7-e793-ac1053533bb3@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Kirill A. Shutemov" Virtualization Exceptions (#VE) are delivered to TDX guests due to specific guest actions which may happen in either user space or the kernel:  * Specific instructions (WBINVD, for example)  * Specific MSR accesses  * Specific CPUID leaf accesses  * Access to TD-shared memory, which includes MMIO In the settings that Linux will run in, virtual exceptions are never generated on accesses to normal, TD-private memory that has been accepted. The entry paths do not access TD-shared memory, MMIO regions or use those specific MSRs, instructions, CPUID leaves that might generate #VE. In addition, all interrupts including NMIs are blocked by the hardware starting with #VE delivery until TDGETVEINFO is called.  This eliminates the chance of a #VE during the syscall gap or paranoid entry paths and simplifies #VE handling. After TDGETVEINFO #VE could happen in theory (e.g. through an NMI), but it is expected not to happen because TDX expects NMIs not to trigger #VEs. Another case where they could happen is if the #VE exception panics, but in this case there are no guarantees on anything anyways. If a guest kernel action which would normally cause a #VE occurs in the interrupt-disabled region before TDGETVEINFO, a #DF is delivered to the guest which will result in an oops (and should eventually be a panic, as we would like to set panic_on_oops to 1 for TDX guests). Add basic infrastructure to handle any #VE which occurs in the kernel or userspace.  Later patches will add handling for specific #VE scenarios. Convert unhandled #VE's (everything, until later in this series) so that they appear just like a #GP by calling ve_raise_fault() directly. ve_raise_fault() is similar to #GP handler and is responsible for sending SIGSEGV to userspace and cpu die and notifying debuggers and other die chain users.   Co-developed-by: Sean Christopherson Signed-off-by: Sean Christopherson Signed-off-by: Kirill A. Shutemov Reviewed-by: Andi Kleen Signed-off-by: Kuppuswamy Sathyanarayanan --- Changes since RFC v2-fix: * No code changes (Added Tony to "To" list) Changes since v1: * Removed [RFC v2 07/32] x86/traps: Add do_general_protection() helper function. * Instead of resuing #GP handler, defined a custom handler. * Fixed commit log as per review comments. arch/x86/include/asm/idtentry.h | 4 ++ arch/x86/include/asm/tdx.h | 19 +++++++++ arch/x86/kernel/idt.c | 6 +++ arch/x86/kernel/tdx.c | 36 +++++++++++++++++ arch/x86/kernel/traps.c | 69 +++++++++++++++++++++++++++++++++ 5 files changed, 134 insertions(+) diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index 5eb3bdf36a41..41a0732d5f68 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -619,6 +619,10 @@ DECLARE_IDTENTRY_XENCB(X86_TRAP_OTHER, exc_xen_hypervisor_callback); DECLARE_IDTENTRY_RAW(X86_TRAP_OTHER, exc_xen_unknown_trap); #endif +#ifdef CONFIG_INTEL_TDX_GUEST +DECLARE_IDTENTRY(X86_TRAP_VE, exc_virtualization_exception); +#endif + /* Device interrupts common/spurious */ DECLARE_IDTENTRY_IRQ(X86_TRAP_OTHER, common_interrupt); #ifdef CONFIG_X86_LOCAL_APIC diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h index fcd42119a287..a451786496a0 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -39,6 +39,25 @@ struct tdx_hypercall_output { u64 r15; }; +/* + * Used by #VE exception handler to gather the #VE exception + * info from the TDX module. This is software only structure + * and not related to TDX module/VMM. + */ +struct ve_info { + u64 exit_reason; + u64 exit_qual; + u64 gla; + u64 gpa; + u32 instr_len; + u32 instr_info; +}; + +unsigned long tdg_get_ve_info(struct ve_info *ve); + +int tdg_handle_virtualization_exception(struct pt_regs *regs, + struct ve_info *ve); + /* Common API to check TDX support in decompression and common kernel code. */ bool is_tdx_guest(void); diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index ee1a283f8e96..546b6b636c7d 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -64,6 +64,9 @@ static const __initconst struct idt_data early_idts[] = { */ INTG(X86_TRAP_PF, asm_exc_page_fault), #endif +#ifdef CONFIG_INTEL_TDX_GUEST + INTG(X86_TRAP_VE, asm_exc_virtualization_exception), +#endif }; /* @@ -87,6 +90,9 @@ static const __initconst struct idt_data def_idts[] = { INTG(X86_TRAP_MF, asm_exc_coprocessor_error), INTG(X86_TRAP_AC, asm_exc_alignment_check), INTG(X86_TRAP_XF, asm_exc_simd_coprocessor_error), +#ifdef CONFIG_INTEL_TDX_GUEST + INTG(X86_TRAP_VE, asm_exc_virtualization_exception), +#endif #ifdef CONFIG_X86_32 TSKG(X86_TRAP_DF, GDT_ENTRY_DOUBLEFAULT_TSS), diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index e4383b416ef3..527d2638ddae 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -10,6 +10,7 @@ /* TDX Module call Leaf IDs */ #define TDINFO 1 +#define TDGETVEINFO 3 static struct { unsigned int gpa_width; @@ -87,6 +88,41 @@ static void tdg_get_info(void) td_info.attributes = out.rdx; } +unsigned long tdg_get_ve_info(struct ve_info *ve) +{ + u64 ret; + struct tdx_module_output out = {0}; + + /* + * NMIs and machine checks are suppressed. Before this point any + * #VE is fatal. After this point (TDGETVEINFO call), NMIs and + * additional #VEs are permitted (but we don't expect them to + * happen unless you panic). + */ + ret = __tdx_module_call(TDGETVEINFO, 0, 0, 0, 0, &out); + + ve->exit_reason = out.rcx; + ve->exit_qual = out.rdx; + ve->gla = out.r8; + ve->gpa = out.r9; + ve->instr_len = out.r10 & UINT_MAX; + ve->instr_info = out.r10 >> 32; + + return ret; +} + +int tdg_handle_virtualization_exception(struct pt_regs *regs, + struct ve_info *ve) +{ + /* + * TODO: Add handler support for various #VE exit + * reasons. It will be added by other patches in + * the series. + */ + pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); + return -EFAULT; +} + void __init tdx_early_init(void) { if (!cpuid_has_tdx_guest()) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 651e3e508959..043608943c3b 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -61,6 +61,7 @@ #include #include #include +#include #ifdef CONFIG_X86_64 #include @@ -1137,6 +1138,74 @@ DEFINE_IDTENTRY(exc_device_not_available) } } +#define VEFSTR "VE fault" +static void ve_raise_fault(struct pt_regs *regs, long error_code) +{ + struct task_struct *tsk = current; + + if (user_mode(regs)) { + tsk->thread.error_code = error_code; + tsk->thread.trap_nr = X86_TRAP_VE; + + /* + * Not fixing up VDSO exceptions similar to #GP handler + * because we don't expect the VDSO to trigger #VE. + */ + show_signal(tsk, SIGSEGV, "", VEFSTR, regs, error_code); + force_sig(SIGSEGV); + return; + } + + if (fixup_exception(regs, X86_TRAP_VE, error_code, 0)) + return; + + tsk->thread.error_code = error_code; + tsk->thread.trap_nr = X86_TRAP_VE; + + /* + * To be potentially processing a kprobe fault and to trust the result + * from kprobe_running(), we have to be non-preemptible. + */ + if (!preemptible() && + kprobe_running() && + kprobe_fault_handler(regs, X86_TRAP_VE)) + return; + + notify_die(DIE_GPF, VEFSTR, regs, error_code, X86_TRAP_VE, SIGSEGV); + + die_addr(VEFSTR, regs, error_code, 0); +} + +#ifdef CONFIG_INTEL_TDX_GUEST +DEFINE_IDTENTRY(exc_virtualization_exception) +{ + struct ve_info ve; + int ret; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU"); + + /* + * NMIs/Machine-checks/Interrupts will be in a disabled state + * till TDGETVEINFO TDCALL is executed. This prevents #VE + * nesting issue. + */ + ret = tdg_get_ve_info(&ve); + + cond_local_irq_enable(regs); + + if (!ret) + ret = tdg_handle_virtualization_exception(regs, &ve); + /* + * If tdg_handle_virtualization_exception() could not process + * it successfully, treat it as #GP(0) and handle it. + */ + if (ret) + ve_raise_fault(regs, 0); + + cond_local_irq_disable(regs); +} +#endif + #ifdef CONFIG_X86_32 DEFINE_IDTENTRY_SW(iret_error) { -- 2.25.1