The following commit has been merged into the x86/urgent branch of tip: Commit-ID: d7e94dbdac1a40924626b0efc7ff530c8baf5e4a Gitweb: https://git.kernel.org/tip/d7e94dbdac1a40924626b0efc7ff530c8baf5e4a Author: Thomas Gleixner <tglx@xxxxxxxxxxxxx> AuthorDate: Fri, 10 Apr 2020 13:54:00 +02:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Sat, 11 Apr 2020 16:39:30 +02:00 x86/split_lock: Provide handle_guest_split_lock() Without at least minimal handling for split lock detection induced #AC, VMX will just run into the same problem as the VMWare hypervisor, which was reported by Kenneth. It will inject the #AC blindly into the guest whether the guest is prepared or not. Provide a function for guest mode which acts depending on the host SLD mode. If mode == sld_warn, treat it like user space, i.e. emit a warning, disable SLD and mark the task accordingly. Otherwise force SIGBUS. [ bp: Add a !CPU_SUP_INTEL stub for handle_guest_split_lock(). ] Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Acked-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Link: https://lkml.kernel.org/r/20200410115516.978037132@xxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20200402123258.895628824@xxxxxxxxxxxxx --- arch/x86/include/asm/cpu.h | 6 ++++++ arch/x86/kernel/cpu/intel.c | 33 ++++++++++++++++++++++++++++----- 2 files changed, 34 insertions(+), 5 deletions(-) diff --git a/arch/x86/include/asm/cpu.h b/arch/x86/include/asm/cpu.h index ff6f3ca..dd17c2d 100644 --- a/arch/x86/include/asm/cpu.h +++ b/arch/x86/include/asm/cpu.h @@ -44,6 +44,7 @@ unsigned int x86_stepping(unsigned int sig); 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 bool handle_guest_split_lock(unsigned long ip); #else static inline void __init cpu_set_core_cap_bits(struct cpuinfo_x86 *c) {} static inline void switch_to_sld(unsigned long tifn) {} @@ -51,5 +52,10 @@ static inline bool handle_user_split_lock(struct pt_regs *regs, long error_code) { return false; } + +static inline bool handle_guest_split_lock(unsigned long ip) +{ + return false; +} #endif #endif /* _ASM_X86_CPU_H */ diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 9a26e97..bf08d45 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -21,6 +21,7 @@ #include <asm/elf.h> #include <asm/cpu_device_id.h> #include <asm/cmdline.h> +#include <asm/traps.h> #ifdef CONFIG_X86_64 #include <linux/topology.h> @@ -1066,13 +1067,10 @@ 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) +static void split_lock_warn(unsigned long ip) { - if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) - return false; - 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 @@ -1081,6 +1079,31 @@ bool handle_user_split_lock(struct pt_regs *regs, long error_code) */ sld_update_msr(false); set_tsk_thread_flag(current, TIF_SLD); +} + +bool handle_guest_split_lock(unsigned long ip) +{ + if (sld_state == sld_warn) { + split_lock_warn(ip); + return true; + } + + pr_warn_once("#AC: %s/%d %s split_lock trap at address: 0x%lx\n", + current->comm, current->pid, + sld_state == sld_fatal ? "fatal" : "bogus", ip); + + current->thread.error_code = 0; + current->thread.trap_nr = X86_TRAP_AC; + force_sig_fault(SIGBUS, BUS_ADRALN, NULL); + return false; +} +EXPORT_SYMBOL_GPL(handle_guest_split_lock); + +bool handle_user_split_lock(struct pt_regs *regs, long error_code) +{ + if ((regs->flags & X86_EFLAGS_AC) || sld_state == sld_fatal) + return false; + split_lock_warn(regs->ip); return true; }
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