Commit-ID: 1499ce2dd45afddea2e84f9f920890cf88384c4e Gitweb: http://git.kernel.org/tip/1499ce2dd45afddea2e84f9f920890cf88384c4e Author: Yu-cheng Yu <yu-cheng...@intel.com> AuthorDate: Fri, 17 Jun 2016 13:07:16 -0700 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Sun, 10 Jul 2016 17:12:10 +0200
x86/fpu/xstate: Fix supervisor xstate component offset CPUID function 0x0d, sub function (i, i > 1) returns in ebx the offset of xstate component i. Zero is returned for a supervisor state. A supervisor state can only be saved by XSAVES and XSAVES uses a compacted format. There is no fixed offset for a supervisor state. This patch checks and makes sure a supervisor state offset is not recorded or mis-used. This has no effect in practice as we currently use no supervisor states, but it would be good to fix. Signed-off-by: Yu-cheng Yu <yu-cheng...@intel.com> Reviewed-by: Dave Hansen <dave.han...@intel.com> Cc: Andy Lutomirski <l...@kernel.org> Cc: Borislav Petkov <b...@alien8.de> Cc: Brian Gerst <brge...@gmail.com> Cc: Dave Hansen <dave.han...@linux.intel.com> Cc: Denys Vlasenko <dvlas...@redhat.com> Cc: Fenghua Yu <fenghua...@intel.com> Cc: H. Peter Anvin <h...@zytor.com> Cc: Josh Poimboeuf <jpoim...@redhat.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Oleg Nesterov <o...@redhat.com> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Quentin Casasnovas <quentin.casasno...@oracle.com> Cc: Ravi V. Shankar <ravi.v.shan...@intel.com> Cc: Sai Praneeth Prakhya <sai.praneeth.prak...@intel.com> Cc: Thomas Gleixner <t...@linutronix.de> Link: http://lkml.kernel.org/r/81b29e40d35d4cec9f2511a856fe769f34935a3f.1466179491.git.yu-cheng...@intel.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- arch/x86/include/asm/fpu/types.h | 1 + arch/x86/include/asm/fpu/xstate.h | 3 ++ arch/x86/kernel/fpu/xstate.c | 62 ++++++++++++++++++++++++--------------- 3 files changed, 43 insertions(+), 23 deletions(-) diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h index 36b90bb..12dd648 100644 --- a/arch/x86/include/asm/fpu/types.h +++ b/arch/x86/include/asm/fpu/types.h @@ -122,6 +122,7 @@ enum xfeature { #define XFEATURE_MASK_OPMASK (1 << XFEATURE_OPMASK) #define XFEATURE_MASK_ZMM_Hi256 (1 << XFEATURE_ZMM_Hi256) #define XFEATURE_MASK_Hi16_ZMM (1 << XFEATURE_Hi16_ZMM) +#define XFEATURE_MASK_PT (1 << XFEATURE_PT_UNIMPLEMENTED_SO_FAR) #define XFEATURE_MASK_PKRU (1 << XFEATURE_PKRU) #define XFEATURE_MASK_FPSSE (XFEATURE_MASK_FP | XFEATURE_MASK_SSE) diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h index d812cf3..92f376c 100644 --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -18,6 +18,9 @@ #define XSAVE_YMM_SIZE 256 #define XSAVE_YMM_OFFSET (XSAVE_HDR_SIZE + XSAVE_HDR_OFFSET) +/* Supervisor features */ +#define XFEATURE_MASK_SUPERVISOR (XFEATURE_MASK_PT) + /* Supported features which support lazy state saving */ #define XFEATURE_MASK_LAZY (XFEATURE_MASK_FP | \ XFEATURE_MASK_SSE | \ diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 7963029..02786fb 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -112,6 +112,27 @@ int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) } EXPORT_SYMBOL_GPL(cpu_has_xfeatures); +static int xfeature_is_supervisor(int xfeature_nr) +{ + /* + * We currently do not support supervisor states, but if + * we did, we could find out like this. + * + * SDM says: If state component 'i' is a user state component, + * ECX[0] return 0; if state component i is a supervisor + * state component, ECX[0] returns 1. + */ + u32 eax, ebx, ecx, edx; + + cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx); + return !!(ecx & 1); +} + +static int xfeature_is_user(int xfeature_nr) +{ + return !xfeature_is_supervisor(xfeature_nr); +} + /* * When executing XSAVEOPT (or other optimized XSAVE instructions), if * a processor implementation detects that an FPU state component is still @@ -230,7 +251,14 @@ static void __init setup_xstate_features(void) continue; cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); - xstate_offsets[i] = ebx; + + /* + * If an xfeature is supervisor state, the offset + * in EBX is invalid. We leave it to -1. + */ + if (xfeature_is_user(i)) + xstate_offsets[i] = ebx; + xstate_sizes[i] = eax; /* * In our xstate size checks, we assume that the @@ -375,32 +403,20 @@ static void __init setup_init_fpu_buf(void) copy_xregs_to_kernel_booting(&init_fpstate.xsave); } -static int xfeature_is_supervisor(int xfeature_nr) -{ - /* - * We currently do not support supervisor states, but if - * we did, we could find out like this. - * - * SDM says: If state component i is a user state component, - * ECX[0] return 0; if state component i is a supervisor - * state component, ECX[0] returns 1. - u32 eax, ebx, ecx, edx; - cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx; - return !!(ecx & 1); - */ - return 0; -} -/* -static int xfeature_is_user(int xfeature_nr) -{ - return !xfeature_is_supervisor(xfeature_nr); -} -*/ - static int xfeature_uncompacted_offset(int xfeature_nr) { u32 eax, ebx, ecx, edx; + /* + * Only XSAVES supports supervisor states and it uses compacted + * format. Checking a supervisor state's uncompacted offset is + * an error. + */ + if (XFEATURE_MASK_SUPERVISOR & (1 << xfeature_nr)) { + WARN_ONCE(1, "No fixed offset for xstate %d\n", xfeature_nr); + return -1; + } + CHECK_XFEATURE(xfeature_nr); cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx); return ebx;
