4.4-stable review patch. If anyone has any objections, please let me know.
------------------ From: yu-cheng yu <[email protected]> commit a5fe93a549c54838063d2952dd9643b0b18aa67f upstream. This issue is a fallout from the command-line parsing move. When "eagerfpu=off" is given as a command-line input, the kernel should disable MPX support. The decision for turning off MPX was made in fpu__init_system_ctx_switch(), which is after the selection of the XSAVE format. This patch fixes it by getting that decision done earlier in fpu__init_system_xstate(). Signed-off-by: Yu-cheng Yu <[email protected]> Cc: Andy Lutomirski <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Dave Hansen <[email protected]> Cc: Fenghua Yu <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Oleg Nesterov <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Quentin Casasnovas <[email protected]> Cc: Ravi V. Shankar <[email protected]> Cc: Sai Praneeth Prakhya <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: yu-cheng yu <[email protected]> Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- arch/x86/include/asm/fpu/internal.h | 1 arch/x86/kernel/fpu/init.c | 56 ++++++++++++++++++++++++++++-------- arch/x86/kernel/fpu/xstate.c | 3 - 3 files changed, 46 insertions(+), 14 deletions(-) --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -42,6 +42,7 @@ extern void fpu__init_cpu_xstate(void); extern void fpu__init_system(struct cpuinfo_x86 *c); extern void fpu__init_check_bugs(void); extern void fpu__resume_cpu(void); +extern u64 fpu__get_supported_xfeatures_mask(void); /* * Debugging facility: --- a/arch/x86/kernel/fpu/init.c +++ b/arch/x86/kernel/fpu/init.c @@ -266,7 +266,45 @@ static void __init fpu__init_system_xsta static enum { AUTO, ENABLE, DISABLE } eagerfpu = AUTO; /* + * Find supported xfeatures based on cpu features and command-line input. + * This must be called after fpu__init_parse_early_param() is called and + * xfeatures_mask is enumerated. + */ +u64 __init fpu__get_supported_xfeatures_mask(void) +{ + /* Support all xfeatures known to us */ + if (eagerfpu != DISABLE) + return XCNTXT_MASK; + + /* Warning of xfeatures being disabled for no eagerfpu mode */ + if (xfeatures_mask & XFEATURE_MASK_EAGER) { + pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n", + xfeatures_mask & XFEATURE_MASK_EAGER); + } + + /* Return a mask that masks out all features requiring eagerfpu mode */ + return ~XFEATURE_MASK_EAGER; +} + +/* + * Disable features dependent on eagerfpu. + */ +static void __init fpu__clear_eager_fpu_features(void) +{ + setup_clear_cpu_cap(X86_FEATURE_MPX); +} + +/* * Pick the FPU context switching strategy: + * + * When eagerfpu is AUTO or ENABLE, we ensure it is ENABLE if either of + * the following is true: + * + * (1) the cpu has xsaveopt, as it has the optimization and doing eager + * FPU switching has a relatively low cost compared to a plain xsave; + * (2) the cpu has xsave features (e.g. MPX) that depend on eager FPU + * switching. Should the kernel boot with noxsaveopt, we support MPX + * with eager FPU switching at a higher cost. */ static void __init fpu__init_system_ctx_switch(void) { @@ -278,19 +316,11 @@ static void __init fpu__init_system_ctx_ WARN_ON_FPU(current->thread.fpu.fpstate_active); current_thread_info()->status = 0; - /* Auto enable eagerfpu for xsaveopt */ if (boot_cpu_has(X86_FEATURE_XSAVEOPT) && eagerfpu != DISABLE) eagerfpu = ENABLE; - if (xfeatures_mask & XFEATURE_MASK_EAGER) { - if (eagerfpu == DISABLE) { - pr_err("x86/fpu: eagerfpu switching disabled, disabling the following xstate features: 0x%llx.\n", - xfeatures_mask & XFEATURE_MASK_EAGER); - xfeatures_mask &= ~XFEATURE_MASK_EAGER; - } else { - eagerfpu = ENABLE; - } - } + if (xfeatures_mask & XFEATURE_MASK_EAGER) + eagerfpu = ENABLE; if (eagerfpu == ENABLE) setup_force_cpu_cap(X86_FEATURE_EAGER_FPU); @@ -308,10 +338,12 @@ static void __init fpu__init_parse_early * No need to check "eagerfpu=auto" again, since it is the * initial default. */ - if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) + if (cmdline_find_option_bool(boot_command_line, "eagerfpu=off")) { eagerfpu = DISABLE; - else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on")) + fpu__clear_eager_fpu_features(); + } else if (cmdline_find_option_bool(boot_command_line, "eagerfpu=on")) { eagerfpu = ENABLE; + } if (cmdline_find_option_bool(boot_command_line, "no387")) setup_clear_cpu_cap(X86_FEATURE_FPU); --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -632,8 +632,7 @@ void __init fpu__init_system_xstate(void BUG(); } - /* Support only the state known to the OS: */ - xfeatures_mask = xfeatures_mask & XCNTXT_MASK; + xfeatures_mask &= fpu__get_supported_xfeatures_mask(); /* Enable xstate instructions to be able to continue with initialization: */ fpu__init_cpu_xstate();
