[PATCH v2 1/2] x86/fpu: Add helper function for tracking AVX512 status

[Noah Goldstein <goldstein.w.n@gmail.com>]

This commit adds a new helper function 'fpu_update_avx_timestamp' to
perform the logic from tracking AVX512 feature use.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
---
Since Borislav Petkov is concerned about adding more macro masks and
inlining the AVX512 status this patch adds a new helper function. This
patch does not change the behavior of the current AVX512 status.

 arch/x86/include/asm/fpu/xstate.h |  1 +
 arch/x86/kernel/fpu/core.c        |  6 ++----
 arch/x86/kernel/fpu/xstate.c      | 13 +++++++++++++
 3 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 109dfcc75299..fe84ac5fb039 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -134,6 +134,7 @@ extern u64 xstate_fx_sw_bytes[USER_XSTATE_FX_SW_WORDS];
 extern void __init update_regset_xstate_info(unsigned int size,
 					     u64 xstate_mask);
 
+void fpu_update_avx_timestamp(struct fpu *fpu);
 void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
 int xfeature_size(int xfeature_nr);
 int copy_uabi_from_kernel_to_xstate(struct xregs_state *xsave, const void *kbuf);
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
index 7ada7bd03a32..6dbf3ee642f9 100644
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -102,11 +102,9 @@ void save_fpregs_to_fpstate(struct fpu *fpu)
 		os_xsave(&fpu->state.xsave);
 
 		/*
-		 * AVX512 state is tracked here because its use is
-		 * known to slow the max clock speed of the core.
+		 * Track of the state of desired avx related xfeatures.
 		 */
-		if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512)
-			fpu->avx512_timestamp = jiffies;
+		fpu_update_avx_timestamp(fpu);
 		return;
 	}
 
diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c
index c8def1b7f8fb..00b495914be2 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1245,6 +1245,19 @@ void xrstors(struct xregs_state *xstate, u64 mask)
 	WARN_ON_ONCE(err);
 }
 
+/*
+ * Track of the state of desired avx architecture features.
+ */
+void fpu_update_avx_timestamp(struct fpu *fpu)
+{
+	/*
+	 * AVX512 state is tracked here because its use is known to slow
+	 * the max clock speed of the core.
+	 */
+	if (fpu->state.xsave.header.xfeatures & XFEATURE_MASK_AVX512)
+		fpu->avx512_timestamp = jiffies;
+}
+
 #ifdef CONFIG_PROC_PID_ARCH_STATUS
 /*
  * Report the amount of time elapsed in millisecond since last AVX512
-- 
2.25.1