linux-kernel - [patch 33/41] x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to

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Date:   Fri, 11 Jun 2021 18:15:56 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Fenghua Yu <fenghua.yu@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Borislav Petkov <bp@...e.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Kan Liang <kan.liang@...ux.intel.com>
Subject: [patch 33/41] x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()

copy_kernel_to_fpregs() restores all xfeatures but it is also the place
where the AMD FXSAVE_LEAK bug is handled.

That prevents fpregs_restore_userregs() to limit the restored features,
which is required to distangle PKRU and XSTATE handling and also for the
upcoming supervisor state management.

Move the FXSAVE_LEAK quirk into __copy_kernel_to_fpregs() and deinline that
function which has become rather fat.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
V4: New patch
---
 arch/x86/include/asm/fpu/internal.h |   25 +------------------------
 arch/x86/kernel/fpu/core.c          |   26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 24 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -399,33 +399,10 @@ static inline int xrstor_from_kernel_err
 extern void save_fpregs_to_fpstate(struct fpu *fpu);
 extern void copy_fpregs_to_fpstate(struct fpu *fpu);
 
-static inline void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
-{
-	if (use_xsave()) {
-		xrstor_from_kernel(&fpstate->xsave, mask);
-	} else {
-		if (use_fxsr())
-			fxrstor_from_kernel(&fpstate->fxsave);
-		else
-			frstor_from_kernel(&fpstate->fsave);
-	}
-}
+extern void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask);
 
 static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
 {
-	/*
-	 * AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
-	 * pending. Clear the x87 state here by setting it to fixed values.
-	 * "m" is a random variable that should be in L1.
-	 */
-	if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) {
-		asm volatile(
-			"fnclex\n\t"
-			"emms\n\t"
-			"fildl %P[addr]"	/* set F?P to defined value */
-			: : [addr] "m" (fpstate));
-	}
-
 	__restore_fpregs_from_fpstate(fpstate, -1);
 }
 
--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -145,6 +145,32 @@ void copy_fpregs_to_fpstate(struct fpu *
 		restore_fpregs_from_fpstate(&fpu->state);
 }
 
+void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
+{
+	/*
+	 * AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception is
+	 * pending. Clear the x87 state here by setting it to fixed values.
+	 * "m" is a random variable that should be in L1.
+	 */
+	if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) {
+		asm volatile(
+			"fnclex\n\t"
+			"emms\n\t"
+			"fildl %P[addr]"	/* set F?P to defined value */
+			: : [addr] "m" (fpstate));
+	}
+
+	if (use_xsave()) {
+		xrstor_from_kernel(&fpstate->xsave, mask);
+	} else {
+		if (use_fxsr())
+			fxrstor_from_kernel(&fpstate->fxsave);
+		else
+			frstor_from_kernel(&fpstate->fsave);
+	}
+}
+EXPORT_SYMBOL_GPL(__restore_fpregs_from_fpstate);
+
 void kernel_fpu_begin_mask(unsigned int kfpu_mask)
 {
 	preempt_disable();