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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6156FC433F5 for ; Sat, 9 Oct 2021 05:38:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48C2760F9C for ; Sat, 9 Oct 2021 05:38:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244447AbhJIFkM (ORCPT ); Sat, 9 Oct 2021 01:40:12 -0400 Received: from mga04.intel.com ([192.55.52.120]:29187 "EHLO mga04.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244323AbhJIFj6 (ORCPT ); Sat, 9 Oct 2021 01:39:58 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10131"; a="225410059" X-IronPort-AV: E=Sophos;i="5.85,360,1624345200"; d="scan'208";a="225410059" Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga104.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Oct 2021 22:38:01 -0700 X-IronPort-AV: E=Sophos;i="5.85,360,1624345200"; d="scan'208";a="569280236" Received: from dmsojoza-mobl3.amr.corp.intel.com (HELO skuppusw-desk1.amr.corp.intel.com) ([10.251.135.62]) by fmsmga002-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 08 Oct 2021 22:38:00 -0700 From: Kuppuswamy Sathyanarayanan To: Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, Paolo Bonzini , David Hildenbrand , Andrea Arcangeli , Josh Poimboeuf , Juergen Gross , Deep Shah , VMware Inc , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel Cc: Peter H Anvin , Dave Hansen , Tony Luck , Dan Williams , Andi Kleen , Kirill Shutemov , Sean Christopherson , Kuppuswamy Sathyanarayanan , linux-kernel@vger.kernel.org Subject: [PATCH v10 06/11] x86/traps: Add #VE support for TDX guest Date: Fri, 8 Oct 2021 22:37:42 -0700 Message-Id: <20211009053747.1694419-7-sathyanarayanan.kuppuswamy@linux.intel.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20211009053747.1694419-1-sathyanarayanan.kuppuswamy@linux.intel.com> References: <20211009053747.1694419-1-sathyanarayanan.kuppuswamy@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 it is expected panic_on_oops is set 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 Reviewed-by: Tony Luck Signed-off-by: Kuppuswamy Sathyanarayanan --- Changes since v9: * None Changes since v8: * Changed tdx_handle_virtualization_exception() return type to bool. * Changed tdx_get_ve_info() return type to bool. * Modified the code to adapt to above return type changes. * In tdx_get_ve_info() added logic to prevent ve update for tdcall failure case. * Renamed TDGETVEINFO to TDX_GET_VEINFO Changes since v7: * None Changes since v6: * None Changes since v5: * Fixed "We" usage in commit log and replaced cpu -> CPU. * Renamed "tdg_" prefix with "tdx_". * Removed TODO comment in tdg_handle_virtualization_exception() as per Boris review comments. * Added comments for ve_raise_fault(). Changes since v4: * Since ve_raise_fault() is used only by TDX code, moved it within #ifdef CONFIG_INTEL_TDX_GUEST. Changes since v3: * None arch/x86/include/asm/idtentry.h | 4 ++ arch/x86/include/asm/tdx.h | 19 ++++++++ arch/x86/kernel/idt.c | 3 ++ arch/x86/kernel/tdx.c | 38 ++++++++++++++++ arch/x86/kernel/traps.c | 77 +++++++++++++++++++++++++++++++++ 5 files changed, 141 insertions(+) diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index 1345088e9902..8ccc81d653b3 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -625,6 +625,10 @@ 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 5f352c5d4d1f..8031d4bfe9ed 100644 --- a/arch/x86/include/asm/tdx.h +++ b/arch/x86/include/asm/tdx.h @@ -39,6 +39,20 @@ 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; /* Guest Linear (virtual) Address */ + u64 gpa; /* Guest Physical (virtual) Address */ + u32 instr_len; + u32 instr_info; +}; + #ifdef CONFIG_INTEL_TDX_GUEST bool is_tdx_guest(void); @@ -52,6 +66,11 @@ u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9, u64 __tdx_hypercall(u64 type, u64 fn, u64 r12, u64 r13, u64 r14, u64 r15, struct tdx_hypercall_output *out); +bool tdx_get_ve_info(struct ve_info *ve); + +bool tdx_handle_virtualization_exception(struct pt_regs *regs, + struct ve_info *ve); + #else static inline bool is_tdx_guest(void) { return false; } diff --git a/arch/x86/kernel/idt.c b/arch/x86/kernel/idt.c index df0fa695bb09..1da074123c16 100644 --- a/arch/x86/kernel/idt.c +++ b/arch/x86/kernel/idt.c @@ -68,6 +68,9 @@ 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 }; /* diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index 3246ffb3606b..1ef979008fe8 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -6,6 +6,9 @@ #include +/* TDX Module call Leaf IDs */ +#define TDX_GET_VEINFO 3 + bool is_tdx_guest(void) { static int tdx_guest = -1; @@ -50,6 +53,41 @@ static inline u64 _tdx_hypercall(u64 fn, u64 r12, u64 r13, u64 r14, return out->r10; } +bool tdx_get_ve_info(struct ve_info *ve) +{ + struct tdx_module_output out; + u64 ret; + + if (!ve) + return false; + + /* + * 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 it is expected not to + * happen unless kernel panics). + */ + ret = __tdx_module_call(TDX_GET_VEINFO, 0, 0, 0, 0, &out); + if (ret) + return false; + + 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 true; +} + +bool tdx_handle_virtualization_exception(struct pt_regs *regs, + struct ve_info *ve) +{ + pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); + return false; +} + void __init tdx_early_init(void) { if (!is_tdx_guest()) diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index a58800973aed..70d76c3a548f 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 @@ -1140,6 +1141,82 @@ DEFINE_IDTENTRY(exc_device_not_available) } } +#ifdef CONFIG_INTEL_TDX_GUEST +#define VE_FAULT_STR "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 it is expected that VDSO doesn't trigger #VE. + */ + show_signal(tsk, SIGSEGV, "", VE_FAULT_STR, regs, error_code); + force_sig(SIGSEGV); + return; + } + + /* + * Attempt to recover from #VE exception failure without + * triggering OOPS (useful for MSR read/write failures) + */ + 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(), it should be non-preemptible. + */ + if (!preemptible() && + kprobe_running() && + kprobe_fault_handler(regs, X86_TRAP_VE)) + return; + + /* Notify about #VE handling failure, useful for debugger hooks */ + if (notify_die(DIE_GPF, VE_FAULT_STR, regs, error_code, + X86_TRAP_VE, SIGSEGV) == NOTIFY_STOP) + return; + + /* Trigger OOPS and panic */ + die_addr(VE_FAULT_STR, regs, error_code, 0); +} + +DEFINE_IDTENTRY(exc_virtualization_exception) +{ + struct ve_info ve; + bool 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 = tdx_get_ve_info(&ve); + + cond_local_irq_enable(regs); + + if (ret) + ret = tdx_handle_virtualization_exception(regs, &ve); + /* + * If tdx_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