[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH] x86: harden use of calc_ler_msr()
Avoid calling the function more than once, thus making sure we won't, under any unusual circumstances, attempt to enable XEN_LER late (which can't work, for setup_force_cpu_cap() being __init. In turn this then allows making the function itself __init, too. While fiddling with section attributes in this area, also move the two involved variables to .data.ro_after_init. Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> --- a/xen/arch/x86/traps.c +++ b/xen/arch/x86/traps.c @@ -126,11 +126,11 @@ DEFINE_PER_CPU_PAGE_ALIGNED(struct tss_p static int debug_stack_lines = 20; integer_param("debug_stack_lines", debug_stack_lines); -static bool opt_ler; +static bool __ro_after_init opt_ler; boolean_param("ler", opt_ler); /* LastExceptionFromIP on this hardware. Zero if LER is not in use. */ -unsigned int __read_mostly ler_msr; +unsigned int __ro_after_init ler_msr; const unsigned int nmi_cpu; @@ -2133,7 +2133,7 @@ static void __init set_intr_gate(unsigne __set_intr_gate(n, 0, addr); } -static unsigned int calc_ler_msr(void) +static unsigned int noinline __init calc_ler_msr(void) { switch ( boot_cpu_data.x86_vendor ) { @@ -2171,8 +2171,17 @@ void percpu_traps_init(void) if ( !opt_ler ) return; - if ( !ler_msr && (ler_msr = calc_ler_msr()) ) + if ( !ler_msr ) + { + ler_msr = calc_ler_msr(); + if ( !ler_msr ) + { + opt_ler = false; + return; + } + setup_force_cpu_cap(X86_FEATURE_XEN_LBR); + } if ( cpu_has_xen_lbr ) wrmsrl(MSR_IA32_DEBUGCTLMSR, IA32_DEBUGCTLMSR_LBR);
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