From c8128cceb4f4b02c53096cb173628184c7e9bc36 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 11 Sep 2014 14:15:11 -0700 Subject: x86: Axe the lightly-used cpu_has_pae cpu_has_pae is only referenced in one place: the X86_32 kexec code (in a file not even built on 64-bit). It hardly warrants its own macro, or the trouble we go to ensuring that it can't be called in X86_64 code. Axe the macro and replace it with a direct cpu feature check. Signed-off-by: Dave Hansen Link: http://lkml.kernel.org/r/20140911211511.AD76E774@viggo.jf.intel.com Acked-by: Borislav Petkov Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/cpufeature.h | 4 ---- 1 file changed, 4 deletions(-) (limited to 'arch/x86/include/asm/cpufeature.h') diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index bb9b258..7b50875 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -300,7 +300,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define cpu_has_de boot_cpu_has(X86_FEATURE_DE) #define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE) #define cpu_has_tsc boot_cpu_has(X86_FEATURE_TSC) -#define cpu_has_pae boot_cpu_has(X86_FEATURE_PAE) #define cpu_has_pge boot_cpu_has(X86_FEATURE_PGE) #define cpu_has_apic boot_cpu_has(X86_FEATURE_APIC) #define cpu_has_sep boot_cpu_has(X86_FEATURE_SEP) @@ -358,9 +357,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #undef cpu_has_vme #define cpu_has_vme 0 -#undef cpu_has_pae -#define cpu_has_pae ___BUG___ - #undef cpu_has_k6_mtrr #define cpu_has_k6_mtrr 0 -- cgit v1.1 From 381aa07a9b4e1f82969203e9e4863da2a157781d Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 11 Sep 2014 14:15:13 -0700 Subject: x86: Introduce disabled-features I believe the REQUIRED_MASK aproach was taken so that it was easier to consult in assembly (arch/x86/kernel/verify_cpu.S). DISABLED_MASK does not have the same restriction, but I implemented it the same way for consistency. We have a REQUIRED_MASK... which does two things: 1. Keeps a list of cpuid bits to check in very early boot and refuse to boot if those are not present. 2. Consulted during cpu_has() checks, which allows us to optimize out things at compile-time. In other words, if we *KNOW* we will not boot with the feature off, then we can safely assume that it will be present forever. But, we don't have a similar mechanism for CPU features which may be present but that we know we will not use. We simply use our existing mechanisms to repeatedly check the status of the bit at runtime (well, the alternatives patching helps here but it does not provide compile-time optimization). Adding a feature to disabled-features.h allows the bit to be checked via a new macro: cpu_feature_enabled(). Note that for features in DISABLED_MASK, checks with this macro have all of the benefits of an #ifdef. Before, we would have done this in a header: #ifdef CONFIG_X86_INTEL_MPX #define cpu_has_mpx cpu_has(X86_FEATURE_MPX) #else #define cpu_has_mpx 0 #endif and this in the code: if (cpu_has_mpx) do_some_mpx_thing(); Now, just add your feature to DISABLED_MASK and you can do this everywhere, and get the same benefits you would have from #ifdefs: if (cpu_feature_enabled(X86_FEATURE_MPX)) do_some_mpx_thing(); We need a new function and *not* a modification to cpu_has() because there are cases where we actually need to check the CPU itself, despite what features the kernel supports. The best example of this is a hypervisor which has no control over what features its guests are using and where the guest does not depend on the host for support. Signed-off-by: Dave Hansen Link: http://lkml.kernel.org/r/20140911211513.9E35E931@viggo.jf.intel.com Acked-by: Borislav Petkov Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/cpufeature.h | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+) (limited to 'arch/x86/include/asm/cpufeature.h') diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 7b50875..1492041 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -8,6 +8,10 @@ #include #endif +#ifndef _ASM_X86_DISABLED_FEATURES_H +#include +#endif + #define NCAPINTS 11 /* N 32-bit words worth of info */ #define NBUGINTS 1 /* N 32-bit bug flags */ @@ -274,6 +278,18 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; (((bit)>>5)==8 && (1UL<<((bit)&31) & REQUIRED_MASK8)) || \ (((bit)>>5)==9 && (1UL<<((bit)&31) & REQUIRED_MASK9)) ) +#define DISABLED_MASK_BIT_SET(bit) \ + ( (((bit)>>5)==0 && (1UL<<((bit)&31) & DISABLED_MASK0)) || \ + (((bit)>>5)==1 && (1UL<<((bit)&31) & DISABLED_MASK1)) || \ + (((bit)>>5)==2 && (1UL<<((bit)&31) & DISABLED_MASK2)) || \ + (((bit)>>5)==3 && (1UL<<((bit)&31) & DISABLED_MASK3)) || \ + (((bit)>>5)==4 && (1UL<<((bit)&31) & DISABLED_MASK4)) || \ + (((bit)>>5)==5 && (1UL<<((bit)&31) & DISABLED_MASK5)) || \ + (((bit)>>5)==6 && (1UL<<((bit)&31) & DISABLED_MASK6)) || \ + (((bit)>>5)==7 && (1UL<<((bit)&31) & DISABLED_MASK7)) || \ + (((bit)>>5)==8 && (1UL<<((bit)&31) & DISABLED_MASK8)) || \ + (((bit)>>5)==9 && (1UL<<((bit)&31) & DISABLED_MASK9)) ) + #define cpu_has(c, bit) \ (__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \ test_cpu_cap(c, bit)) @@ -282,6 +298,18 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; (__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \ x86_this_cpu_test_bit(bit, (unsigned long *)&cpu_info.x86_capability)) +/* + * This macro is for detection of features which need kernel + * infrastructure to be used. It may *not* directly test the CPU + * itself. Use the cpu_has() family if you want true runtime + * testing of CPU features, like in hypervisor code where you are + * supporting a possible guest feature where host support for it + * is not relevant. + */ +#define cpu_feature_enabled(bit) \ + (__builtin_constant_p(bit) && DISABLED_MASK_BIT_SET(bit) ? 0 : \ + cpu_has(&boot_cpu_data, bit)) + #define boot_cpu_has(bit) cpu_has(&boot_cpu_data, bit) #define set_cpu_cap(c, bit) set_bit(bit, (unsigned long *)((c)->x86_capability)) -- cgit v1.1 From 9298b815efe500b272e4084ed05eeae7a92b5340 Mon Sep 17 00:00:00 2001 From: Dave Hansen Date: Thu, 11 Sep 2014 14:15:24 -0700 Subject: x86: Add more disabled features The original motivation for these patches was for an Intel CPU feature called MPX. The patch to add a disabled feature for it will go in with the other parts of the support. But, in the meantime, there are a few other features than MPX that we can make assumptions about at compile-time based on compile options. Add them to disabled-features.h and check them with cpu_feature_enabled(). Note that this gets rid of the last things that needed an #ifdef CONFIG_X86_64 in cpufeature.h. Yay! Signed-off-by: Dave Hansen Link: http://lkml.kernel.org/r/20140911211524.C0EC332A@viggo.jf.intel.com Acked-by: Borislav Petkov Signed-off-by: H. Peter Anvin --- arch/x86/include/asm/cpufeature.h | 20 -------------------- 1 file changed, 20 deletions(-) (limited to 'arch/x86/include/asm/cpufeature.h') diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h index 1492041..42db503 100644 --- a/arch/x86/include/asm/cpufeature.h +++ b/arch/x86/include/asm/cpufeature.h @@ -324,7 +324,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; } while (0) #define cpu_has_fpu boot_cpu_has(X86_FEATURE_FPU) -#define cpu_has_vme boot_cpu_has(X86_FEATURE_VME) #define cpu_has_de boot_cpu_has(X86_FEATURE_DE) #define cpu_has_pse boot_cpu_has(X86_FEATURE_PSE) #define cpu_has_tsc boot_cpu_has(X86_FEATURE_TSC) @@ -343,9 +342,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define cpu_has_avx2 boot_cpu_has(X86_FEATURE_AVX2) #define cpu_has_ht boot_cpu_has(X86_FEATURE_HT) #define cpu_has_nx boot_cpu_has(X86_FEATURE_NX) -#define cpu_has_k6_mtrr boot_cpu_has(X86_FEATURE_K6_MTRR) -#define cpu_has_cyrix_arr boot_cpu_has(X86_FEATURE_CYRIX_ARR) -#define cpu_has_centaur_mcr boot_cpu_has(X86_FEATURE_CENTAUR_MCR) #define cpu_has_xstore boot_cpu_has(X86_FEATURE_XSTORE) #define cpu_has_xstore_enabled boot_cpu_has(X86_FEATURE_XSTORE_EN) #define cpu_has_xcrypt boot_cpu_has(X86_FEATURE_XCRYPT) @@ -380,22 +376,6 @@ extern const char * const x86_bug_flags[NBUGINTS*32]; #define cpu_has_eager_fpu boot_cpu_has(X86_FEATURE_EAGER_FPU) #define cpu_has_topoext boot_cpu_has(X86_FEATURE_TOPOEXT) -#ifdef CONFIG_X86_64 - -#undef cpu_has_vme -#define cpu_has_vme 0 - -#undef cpu_has_k6_mtrr -#define cpu_has_k6_mtrr 0 - -#undef cpu_has_cyrix_arr -#define cpu_has_cyrix_arr 0 - -#undef cpu_has_centaur_mcr -#define cpu_has_centaur_mcr 0 - -#endif /* CONFIG_X86_64 */ - #if __GNUC__ >= 4 extern void warn_pre_alternatives(void); extern bool __static_cpu_has_safe(u16 bit); -- cgit v1.1