diff options
Diffstat (limited to 'arch/x86/kernel/fred.c')
| -rw-r--r-- | arch/x86/kernel/fred.c | 60 |
1 files changed, 47 insertions, 13 deletions
diff --git a/arch/x86/kernel/fred.c b/arch/x86/kernel/fred.c index 4bcd8791ad96..816187da3a47 100644 --- a/arch/x86/kernel/fred.c +++ b/arch/x86/kernel/fred.c @@ -3,6 +3,7 @@ #include <asm/desc.h> #include <asm/fred.h> +#include <asm/msr.h> #include <asm/tlbflush.h> #include <asm/traps.h> @@ -21,32 +22,45 @@ #define FRED_STKLVL(vector, lvl) ((lvl) << (2 * (vector))) +DEFINE_PER_CPU(unsigned long, fred_rsp0); +EXPORT_PER_CPU_SYMBOL(fred_rsp0); + void cpu_init_fred_exceptions(void) { /* When FRED is enabled by default, remove this log message */ pr_info("Initialize FRED on CPU%d\n", smp_processor_id()); - wrmsrl(MSR_IA32_FRED_CONFIG, + /* + * If a kernel event is delivered before a CPU goes to user level for + * the first time, its SS is NULL thus NULL is pushed into the SS field + * of the FRED stack frame. But before ERETS is executed, the CPU may + * context switch to another task and go to user level. Then when the + * CPU comes back to kernel mode, SS is changed to __KERNEL_DS. Later + * when ERETS is executed to return from the kernel event handler, a #GP + * fault is generated because SS doesn't match the SS saved in the FRED + * stack frame. + * + * Initialize SS to __KERNEL_DS when enabling FRED to avoid such #GPs. + */ + loadsegment(ss, __KERNEL_DS); + + wrmsrq(MSR_IA32_FRED_CONFIG, /* Reserve for CALL emulation */ FRED_CONFIG_REDZONE | FRED_CONFIG_INT_STKLVL(0) | FRED_CONFIG_ENTRYPOINT(asm_fred_entrypoint_user)); + wrmsrq(MSR_IA32_FRED_STKLVLS, 0); + /* - * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* - * (remember that user space faults are always taken on stack level 0) - * is to avoid overflowing the kernel stack. + * Ater a CPU offline/online cycle, the FRED RSP0 MSR should be + * resynchronized with its per-CPU cache. */ - wrmsrl(MSR_IA32_FRED_STKLVLS, - FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) | - FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) | - FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) | - FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); + wrmsrq(MSR_IA32_FRED_RSP0, __this_cpu_read(fred_rsp0)); - /* The FRED equivalents to IST stacks... */ - wrmsrl(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); - wrmsrl(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); - wrmsrl(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); + wrmsrq(MSR_IA32_FRED_RSP1, 0); + wrmsrq(MSR_IA32_FRED_RSP2, 0); + wrmsrq(MSR_IA32_FRED_RSP3, 0); /* Enable FRED */ cr4_set_bits(X86_CR4_FRED); @@ -57,3 +71,23 @@ void cpu_init_fred_exceptions(void) setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); } + +/* Must be called after setup_cpu_entry_areas() */ +void cpu_init_fred_rsps(void) +{ + /* + * The purpose of separate stacks for NMI, #DB and #MC *in the kernel* + * (remember that user space faults are always taken on stack level 0) + * is to avoid overflowing the kernel stack. + */ + wrmsrq(MSR_IA32_FRED_STKLVLS, + FRED_STKLVL(X86_TRAP_DB, FRED_DB_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_NMI, FRED_NMI_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_MC, FRED_MC_STACK_LEVEL) | + FRED_STKLVL(X86_TRAP_DF, FRED_DF_STACK_LEVEL)); + + /* The FRED equivalents to IST stacks... */ + wrmsrq(MSR_IA32_FRED_RSP1, __this_cpu_ist_top_va(DB)); + wrmsrq(MSR_IA32_FRED_RSP2, __this_cpu_ist_top_va(NMI)); + wrmsrq(MSR_IA32_FRED_RSP3, __this_cpu_ist_top_va(DF)); +} |