From 50f408d96d4d1a945d2c50c5fd8ed400883edf0e Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Fri, 3 Jul 2020 05:49:27 -0700 Subject: [PATCH] x86/fpu/xstate: Add helpers for LBR dynamic supervisor feature The perf subsystem will only need to save/restore the LBR state. However, the existing helpers save all supported supervisor states to a kernel buffer, which will be unnecessary. Two helpers are introduced to only save/restore requested dynamic supervisor states. The supervisor features in XFEATURE_MASK_SUPERVISOR_SUPPORTED and XFEATURE_MASK_SUPERVISOR_UNSUPPORTED mask cannot be saved/restored using these helpers. The helpers will be used in the following patch. Signed-off-by: Kan Liang Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dave Hansen Link: https://lkml.kernel.org/r/1593780569-62993-22-git-send-email-kan.liang@linux.intel.com --- arch/x86/include/asm/fpu/xstate.h | 3 ++ arch/x86/kernel/fpu/xstate.c | 72 +++++++++++++++++++++++++++++++++++++++ 2 files changed, 75 insertions(+) diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h index 040c4d4..c029fce 100644 --- a/arch/x86/include/asm/fpu/xstate.h +++ b/arch/x86/include/asm/fpu/xstate.h @@ -106,6 +106,9 @@ int copy_xstate_to_user(void __user *ubuf, struct xregs_state *xsave, unsigned i int copy_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf); int copy_user_to_xstate(struct xregs_state *xsave, const void __user *ubuf); void copy_supervisor_to_kernel(struct xregs_state *xsave); +void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask); +void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask); + /* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ int validate_user_xstate_header(const struct xstate_header *hdr); diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index dcf0624..b0c22b7 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1361,6 +1361,78 @@ void copy_supervisor_to_kernel(struct xregs_state *xstate) } } +/** + * copy_dynamic_supervisor_to_kernel() - Save dynamic supervisor states to + * an xsave area + * @xstate: A pointer to an xsave area + * @mask: Represent the dynamic supervisor features saved into the xsave area + * + * Only the dynamic supervisor states sets in the mask are saved into the xsave + * area (See the comment in XFEATURE_MASK_DYNAMIC for the details of dynamic + * supervisor feature). Besides the dynamic supervisor states, the legacy + * region and XSAVE header are also saved into the xsave area. The supervisor + * features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and + * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not saved. + * + * The xsave area must be 64-bytes aligned. + */ +void copy_dynamic_supervisor_to_kernel(struct xregs_state *xstate, u64 mask) +{ + u64 dynamic_mask = xfeatures_mask_dynamic() & mask; + u32 lmask, hmask; + int err; + + if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES))) + return; + + if (WARN_ON_FPU(!dynamic_mask)) + return; + + lmask = dynamic_mask; + hmask = dynamic_mask >> 32; + + XSTATE_OP(XSAVES, xstate, lmask, hmask, err); + + /* Should never fault when copying to a kernel buffer */ + WARN_ON_FPU(err); +} + +/** + * copy_kernel_to_dynamic_supervisor() - Restore dynamic supervisor states from + * an xsave area + * @xstate: A pointer to an xsave area + * @mask: Represent the dynamic supervisor features restored from the xsave area + * + * Only the dynamic supervisor states sets in the mask are restored from the + * xsave area (See the comment in XFEATURE_MASK_DYNAMIC for the details of + * dynamic supervisor feature). Besides the dynamic supervisor states, the + * legacy region and XSAVE header are also restored from the xsave area. The + * supervisor features in the XFEATURE_MASK_SUPERVISOR_SUPPORTED and + * XFEATURE_MASK_SUPERVISOR_UNSUPPORTED are not restored. + * + * The xsave area must be 64-bytes aligned. + */ +void copy_kernel_to_dynamic_supervisor(struct xregs_state *xstate, u64 mask) +{ + u64 dynamic_mask = xfeatures_mask_dynamic() & mask; + u32 lmask, hmask; + int err; + + if (WARN_ON_FPU(!boot_cpu_has(X86_FEATURE_XSAVES))) + return; + + if (WARN_ON_FPU(!dynamic_mask)) + return; + + lmask = dynamic_mask; + hmask = dynamic_mask >> 32; + + XSTATE_OP(XRSTORS, xstate, lmask, hmask, err); + + /* Should never fault when copying from a kernel buffer */ + WARN_ON_FPU(err); +} + #ifdef CONFIG_PROC_PID_ARCH_STATUS /* * Report the amount of time elapsed in millisecond since last AVX512 -- 2.7.4