Messages in this thread | | | Date | Thu, 4 Jan 2018 19:34:30 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH 7/7] x86/microcode: Recheck IBRS features on microcode reload |
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On Thu, Jan 04, 2018 at 07:28:58PM +0100, Borislav Petkov wrote: > On Thu, Jan 04, 2018 at 09:56:48AM -0800, Tim Chen wrote: > > On new microcode write, check whether IBRS > > is present by rescanning scattered CPU features. > > > > Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com> > > --- > > arch/x86/kernel/cpu/microcode/core.c | 6 ++++++ > > 1 file changed, 6 insertions(+) > > > > diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c > > index c4fa4a8..44b9355 100644 > > --- a/arch/x86/kernel/cpu/microcode/core.c > > +++ b/arch/x86/kernel/cpu/microcode/core.c > > @@ -40,6 +40,7 @@ > > #include <asm/processor.h> > > #include <asm/cmdline.h> > > #include <asm/setup.h> > > +#include <asm/spec_ctrl.h> > > > > #define DRIVER_VERSION "2.2" > > > > @@ -444,6 +445,11 @@ static ssize_t microcode_write(struct file *file, const char __user *buf, > > if (ret > 0) > > perf_check_microcode(); > > > > + /* check spec_ctrl capabilities */ > > + mutex_lock(&spec_ctrl_mutex); > > + init_scattered_cpuid_features(&boot_cpu_data); > > No need for that - make a specific function like perf_check_microcode() > which checks only the IBRS bit and updates stuff accordingly.
It would be better I agree. I've got this:
void spec_ctrl_rescan_cpuid(void) { int cpu;
if (use_ibp_disable) return; mutex_lock(&spec_ctrl_mutex); if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL || boot_cpu_data.x86_vendor == X86_VENDOR_AMD) { /* detect spec ctrl related cpuid additions */ init_scattered_cpuid_features(&boot_cpu_data); spec_ctrl_init(&boot_cpu_data);
/* * The SPEC_CTRL and IBPB_SUPPORT cpuid bits may have * just been set in the boot_cpu_data, transfer them * to the per-cpu data too. This must run after * spec_ctrl_init() to take care of * setup_force_cpu_cap() too. */ if (cpu_has_spec_ctrl()) for_each_online_cpu(cpu) set_cpu_cap(&cpu_data(cpu), X86_FEATURE_SPEC_CTRL); if (boot_cpu_has(X86_FEATURE_IBPB_SUPPORT)) for_each_online_cpu(cpu) set_cpu_cap(&cpu_data(cpu), X86_FEATURE_IBPB_SUPPORT); } mutex_unlock(&spec_ctrl_mutex); }
However we've to start somewhere so that is a simpler start..
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