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=-1.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, HK_RANDOM_FROM,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=no 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 50C7FC2BB55 for ; Fri, 10 Apr 2020 04:39:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22C6D20CC7 for ; Fri, 10 Apr 2020 04:39:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725924AbgDJEjJ (ORCPT ); Fri, 10 Apr 2020 00:39:09 -0400 Received: from mga03.intel.com ([134.134.136.65]:30517 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725816AbgDJEjJ (ORCPT ); Fri, 10 Apr 2020 00:39:09 -0400 IronPort-SDR: 2BJ+npPKlQq6zmJk0s+5XiJqXGTsEFsKE36dKcewe+xXvj5qn8VJkFKmV7KYyGippxSd0S04z2 tctqwxVNqvrw== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by orsmga103.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Apr 2020 21:39:08 -0700 IronPort-SDR: Jex1LB4E6zchpFErZFN8+QynTiqL4KPnMsJWsneV7BzINT8v7kXR7vUkJw5FqYxQ48Z3rzUN3D u/k47D0ACMjg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.72,364,1580803200"; d="scan'208";a="276067089" Received: from xiaoyaol-mobl.ccr.corp.intel.com (HELO [10.255.28.169]) ([10.255.28.169]) by fmsmga004.fm.intel.com with ESMTP; 09 Apr 2020 21:39:04 -0700 Subject: Re: [PATCH 2/3] x86/split_lock: Refactor and export handle_user_split_lock() for KVM To: Thomas Gleixner , Sean Christopherson , Paolo Bonzini Cc: x86@kernel.org, "Kenneth R . Crudup" , Fenghua Yu , Nadav Amit , Thomas Hellstrom , Tony Luck , Peter Zijlstra , Jessica Yu , Steven Rostedt , Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , kvm@vger.kernel.org, linux-kernel@vger.kernel.org References: <20200402124205.334622628@linutronix.de> <20200402155554.27705-1-sean.j.christopherson@intel.com> <20200402155554.27705-3-sean.j.christopherson@intel.com> <87v9mhn7nf.fsf@nanos.tec.linutronix.de> <20200402171946.GH13879@linux.intel.com> <87mu7tn1w8.fsf@nanos.tec.linutronix.de> From: Xiaoyao Li Message-ID: <716f5824-8d47-24cc-4935-c2dd32ed4629@intel.com> Date: Fri, 10 Apr 2020 12:39:03 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <87mu7tn1w8.fsf@nanos.tec.linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 4/3/2020 3:06 AM, Thomas Gleixner wrote: > Sean Christopherson writes: >> On Thu, Apr 02, 2020 at 07:01:56PM +0200, Thomas Gleixner wrote: >>>> static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {} >>>> static inline void switch_to_sld(unsigned long tifn) {} >>>> -static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code) >>>> +static inline bool handle_user_split_lock(unsigned long ip) >>> >>> This is necessary because VMX can be compiled without CPU_SUP_INTEL? >> >> Ya, it came about when cleaning up the IA32_FEATURE_CONTROL MSR handling >> to consolidate duplicate code. >> >> config KVM_INTEL >> tristate "KVM for Intel (and compatible) processors support" >> depends on KVM && IA32_FEAT_CTL >> >> config IA32_FEAT_CTL >> def_bool y >> depends on CPU_SUP_INTEL || CPU_SUP_CENTAUR || CPU_SUP_ZHAOXIN > > Ah, indeed. So something like the below would make sense. Hmm? > > Of course that can be mangled into Xiaoyao's patches, I'm not worried > about my patch count :) > I don't mind using yours in my next version. Hi Paolo, Are you OK with the kvm part below? If no objection, I can spin the next version using tglx's. > > 8<---------------- > --- a/arch/x86/include/asm/cpu.h > +++ b/arch/x86/include/asm/cpu.h > @@ -43,14 +43,14 @@ unsigned int x86_stepping(unsigned int s > #ifdef CONFIG_CPU_SUP_INTEL > extern void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c); > extern void switch_to_sld(unsigned long tifn); > -extern bool handle_user_split_lock(struct pt_regs *regs, long error_code); > +extern int handle_ac_split_lock(unsigned long ip); > extern void split_lock_validate_module_text(struct module *me, void *text, void *text_end); > #else > static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {} > static inline void switch_to_sld(unsigned long tifn) {} > -static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code) > +static int handle_ac_split_lock(unsigned long ip) > { > - return false; > + return -ENOSYS; > } > static inline void split_lock_validate_module_text(struct module *me, void *text, void *text_end) {} > #endif > > --- a/arch/x86/kernel/cpu/intel.c > +++ b/arch/x86/kernel/cpu/intel.c > @@ -1102,13 +1102,20 @@ static void split_lock_init(void) > split_lock_verify_msr(sld_state != sld_off); > } > > -bool handle_user_split_lock(struct pt_regs *regs, long error_code) > +int handle_ac_split_lock(unsigned long ip) > { > - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) > - return false; > + switch (sld_state) { > + case sld_warn: > + break; > + case sld_off: > + pr_warn_once("#AC: Spurious trap at address: 0x%lx\n", ip); > + return -ENOSYS; > + case sld_fatal: > + return -EFAULT; > + } > > pr_warn_ratelimited("#AC: %s/%d took a split_lock trap at address: 0x%lx\n", > - current->comm, current->pid, regs->ip); > + current->comm, current->pid, ip); > > /* > * Disable the split lock detection for this task so it can make > @@ -1117,8 +1124,9 @@ bool handle_user_split_lock(struct pt_re > */ > sld_update_msr(false); > set_tsk_thread_flag(current, TIF_SLD); > - return true; > + return 0; > } > +EXPORT_SYMBOL_GPL(handle_ac_split_lock); > > /* > * This function is called only when switching between tasks with > --- a/arch/x86/kernel/traps.c > +++ b/arch/x86/kernel/traps.c > @@ -304,7 +304,7 @@ dotraplinkage void do_alignment_check(st > > local_irq_enable(); > > - if (handle_user_split_lock(regs, error_code)) > + if (!(regs->flags & X86_EFLAGS_AC) && !handle_ac_split_lock(regs->ip)) > return; > > do_trap(X86_TRAP_AC, SIGBUS, "alignment check", regs, > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -65,6 +65,7 @@ > > MODULE_AUTHOR("Qumranet"); > MODULE_LICENSE("GPL"); > +MODULE_INFO(sld_safe, "Y"); > > #ifdef MODULE > static const struct x86_cpu_id vmx_cpu_id[] = { > @@ -4623,6 +4624,22 @@ static int handle_machine_check(struct k > return 1; > } > > +static bool guest_handles_ac(struct kvm_vcpu *vcpu) > +{ > + /* > + * If guest has alignment checking enabled in CR0 and activated in > + * eflags, then the #AC originated from CPL3 and the guest is able > + * to handle it. It does not matter whether this is a regular or > + * a split lock operation induced #AC. > + */ > + if (vmx_get_cpl(vcpu) == 3 && kvm_read_cr0_bits(vcpu, X86_CR0_AM) && > + kvm_get_rflags(vcpu) & X86_EFLAGS_AC) > + return true; > + > + /* Add guest SLD handling checks here once it's supported */ > + return false; > +} > + > static int handle_exception_nmi(struct kvm_vcpu *vcpu) > { > struct vcpu_vmx *vmx = to_vmx(vcpu); > @@ -4630,6 +4647,7 @@ static int handle_exception_nmi(struct k > u32 intr_info, ex_no, error_code; > unsigned long cr2, rip, dr6; > u32 vect_info; > + int err; > > vect_info = vmx->idt_vectoring_info; > intr_info = vmx->exit_intr_info; > @@ -4688,9 +4706,6 @@ static int handle_exception_nmi(struct k > return handle_rmode_exception(vcpu, ex_no, error_code); > > switch (ex_no) { > - case AC_VECTOR: > - kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); > - return 1; > case DB_VECTOR: > dr6 = vmcs_readl(EXIT_QUALIFICATION); > if (!(vcpu->guest_debug & > @@ -4719,6 +4734,29 @@ static int handle_exception_nmi(struct k > kvm_run->debug.arch.pc = vmcs_readl(GUEST_CS_BASE) + rip; > kvm_run->debug.arch.exception = ex_no; > break; > + case AC_VECTOR: > + if (guest_handles_ac(vcpu)) { > + kvm_queue_exception_e(vcpu, AC_VECTOR, error_code); > + return 1; > + } > + /* > + * Handle #AC caused by split lock detection. If the host > + * mode is sld_warn, then it warns, marks current with > + * TIF_SLD and disables split lock detection. So the guest > + * can just continue. > + * > + * If the host mode is fatal, the handling code warned. Let > + * qemu kill itself. > + * > + * If the host mode is off, then this #AC is bonkers and > + * something is badly wrong. Let it fail as well. > + */ > + err = handle_ac_split_lock(kvm_rip_read(vcpu)); > + if (!err) > + return 1; > + /* Propagate the error type to user space */ > + error_code = err == -EFAULT ? 0x100 : 0x200; > + fallthrough; > default: > kvm_run->exit_reason = KVM_EXIT_EXCEPTION; > kvm_run->ex.exception = ex_no; >