diff options
| -rw-r--r-- | arch/x86/include/asm/fpu/types.h | 15 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 60 |
2 files changed, 59 insertions, 16 deletions
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index c49c517..6aaafe0 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -159,22 +159,19 @@ struct xstate_header { u64 reserved[6]; } __attribute__((packed)); -/* New processor state extensions should be added here: */ -#define XSTATE_RESERVE (sizeof(struct ymmh_struct) + \ - sizeof(struct lwp_struct) + \ - sizeof(struct mpx_struct) ) /* * This is our most modern FPU state format, as saved by the XSAVE * and restored by the XRSTOR instructions. * * It consists of a legacy fxregs portion, an xstate header and - * subsequent fixed size areas as defined by the xstate header. - * Not all CPUs support all the extensions. + * subsequent areas as defined by the xstate header. Not all CPUs + * support all the extensions, so the size of the extended area + * can vary quite a bit between CPUs. */ struct xregs_state { struct fxregs_state i387; struct xstate_header header; - u8 __reserved[XSTATE_RESERVE]; + u8 extended_state_area[0]; } __attribute__ ((packed, aligned (64))); /* @@ -182,7 +179,9 @@ struct xregs_state { * put together, so that we can pick the right one runtime. * * The size of the structure is determined by the largest - * member - which is the xsave area: + * member - which is the xsave area. The padding is there + * to ensure that statically-allocated task_structs (just + * the init_task today) have enough space. */ union fpregs_state { struct fregs_state fsave; diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 2ada11c..769603a 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -312,24 +312,64 @@ static void __init setup_init_fpu_buf(void) /* * Calculate total size of enabled xstates in XCR0/xfeatures_mask. */ -static void __init init_xstate_size(void) +static unsigned int __init calculate_xstate_size(void) { unsigned int eax, ebx, ecx, edx; + unsigned int calculated_xstate_size; int i; if (!cpu_has_xsaves) { cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); - xstate_size = ebx; - return; + calculated_xstate_size = ebx; + return calculated_xstate_size; } - xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE; + calculated_xstate_size = FXSAVE_SIZE + XSAVE_HDR_SIZE; for (i = 2; i < 64; i++) { if (test_bit(i, (unsigned long *)&xfeatures_mask)) { cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); - xstate_size += eax; + calculated_xstate_size += eax; } } + return calculated_xstate_size; +} + +/* + * Will the runtime-enumerated 'xstate_size' fit in the init + * task's statically-allocated buffer? + */ +static bool is_supported_xstate_size(unsigned int test_xstate_size) +{ + if (test_xstate_size <= sizeof(union fpregs_state)) + return true; + + pr_warn("x86/fpu: xstate buffer too small (%zu < %d), disabling xsave\n", + sizeof(union fpregs_state), test_xstate_size); + return false; +} + +static int init_xstate_size(void) +{ + /* Recompute the context size for enabled features: */ + unsigned int possible_xstate_size = calculate_xstate_size(); + + /* Ensure we have the space to store all enabled: */ + if (!is_supported_xstate_size(possible_xstate_size)) + return -EINVAL; + + /* + * The size is OK, we are definitely going to use xsave, + * make it known to the world that we need more space. + */ + xstate_size = possible_xstate_size; + return 0; +} + +void fpu__init_disable_system_xstate(void) +{ + xfeatures_mask = 0; + cr4_clear_bits(X86_CR4_OSXSAVE); + fpu__xstate_clear_all_cpu_caps(); } /* @@ -340,6 +380,7 @@ void __init fpu__init_system_xstate(void) { unsigned int eax, ebx, ecx, edx; static int on_boot_cpu = 1; + int err; WARN_ON_FPU(!on_boot_cpu); on_boot_cpu = 0; @@ -367,9 +408,12 @@ void __init fpu__init_system_xstate(void) /* Enable xstate instructions to be able to continue with initialization: */ fpu__init_cpu_xstate(); - - /* Recompute the context size for enabled features: */ - init_xstate_size(); + err = init_xstate_size(); + if (err) { + /* something went wrong, boot without any XSAVE support */ + fpu__init_disable_system_xstate(); + return; + } update_regset_xstate_info(xstate_size, xfeatures_mask); fpu__init_prepare_fx_sw_frame(); |