Commit-ID: facbf4d91ae64f84ef93a00e4037135cd9f4b2ab Gitweb: http://git.kernel.org/tip/facbf4d91ae64f84ef93a00e4037135cd9f4b2ab Author: Fenghua Yu <fenghua...@intel.com> AuthorDate: Thu, 29 May 2014 11:12:38 -0700 Committer: H. Peter Anvin <h...@linux.intel.com> CommitDate: Thu, 29 May 2014 14:32:57 -0700
x86/xsaves: Use xsave/xrstor for saving and restoring user space context We use legacy xsave/xrstor to save and restore standard form of xsave area in user space context. No xsaveopt or xsaves is used here for two reasons. First, we don't want to use modified optimization which is implemented in xsaveopt and xsaves because xrstor/xrstors might track a wrong user space application. Secondly, we don't use compacted format of xsave area for backward compatibility because legacy user space applications only don't understand the compacted format of the xsave area. Using standard form of the xsave area may allocate more memory for user context than compacted form, but preserves compatibility with legacy applications. Furthermore, even with holes, the relevant cache lines don't get touched and thus the performance impact is limited. Signed-off-by: Fenghua Yu <fenghua...@intel.com> Link: http://lkml.kernel.org/r/1401387164-43416-11-git-send-email-fenghua...@intel.com Signed-off-by: H. Peter Anvin <h...@linux.intel.com> --- arch/x86/include/asm/xsave.h | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-) diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h index 8b75824..0d15231 100644 --- a/arch/x86/include/asm/xsave.h +++ b/arch/x86/include/asm/xsave.h @@ -145,6 +145,16 @@ static inline int fpu_xrstor_checking(struct xsave_struct *fx) return xrstor_state(fx, -1); } +/* + * Save xstate to user space xsave area. + * + * We don't use modified optimization because xrstor/xrstors might track + * a different application. + * + * We don't use compacted format xsave area for + * backward compatibility for old applications which don't understand + * compacted format of xsave area. + */ static inline int xsave_user(struct xsave_struct __user *buf) { int err; @@ -158,35 +168,28 @@ static inline int xsave_user(struct xsave_struct __user *buf) return -EFAULT; __asm__ __volatile__(ASM_STAC "\n" - "1: .byte " REX_PREFIX "0x0f,0xae,0x27\n" + "1:"XSAVE"\n" "2: " ASM_CLAC "\n" - ".section .fixup,\"ax\"\n" - "3: movl $-1,%[err]\n" - " jmp 2b\n" - ".previous\n" - _ASM_EXTABLE(1b,3b) - : [err] "=r" (err) + xstate_fault : "D" (buf), "a" (-1), "d" (-1), "0" (0) : "memory"); return err; } +/* + * Restore xstate from user space xsave area. + */ static inline int xrestore_user(struct xsave_struct __user *buf, u64 mask) { - int err; + int err = 0; struct xsave_struct *xstate = ((__force struct xsave_struct *)buf); u32 lmask = mask; u32 hmask = mask >> 32; __asm__ __volatile__(ASM_STAC "\n" - "1: .byte " REX_PREFIX "0x0f,0xae,0x2f\n" + "1:"XRSTOR"\n" "2: " ASM_CLAC "\n" - ".section .fixup,\"ax\"\n" - "3: movl $-1,%[err]\n" - " jmp 2b\n" - ".previous\n" - _ASM_EXTABLE(1b,3b) - : [err] "=r" (err) + xstate_fault : "D" (xstate), "a" (lmask), "d" (hmask), "0" (0) : "memory"); /* memory required? */ return err; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/