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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@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Link: https://lkml.kernel.org/r/20200410115516.978037132@linutronix.de
Link: https://lkml.kernel.org/r/20200402123258.895628824@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-04-10 13:54:00 +02:00 committed by Borislav Petkov
parent 5b8b9d0c6d
commit d7e94dbdac
2 changed files with 34 additions and 5 deletions
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6
arch/x86/include/asm/cpu.h
View File

@ -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 */

33
arch/x86/kernel/cpu/intel.c
View File

@ -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;
}