x86/fpu: Add XFD state to fpstate

Add storage for XFD register state to struct fpstate. This will be used to store the XFD MSR state. This will be used for switching the XFD MSR when FPU content is restored. Add a per-CPU variable to cache the current MSR value so the MSR has only to be written when the values are different. Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Signed-off-by: Borislav Petkov <bp@suse.de> Link: https://lkml.kernel.org/r/20211021225527.10184-15-chang.seok.bae@intel.com
mariux64 · Oct 26, 2021 · 8bf2675 · 8bf2675
1 parent dae1bd5
commit 8bf2675
Show file tree

Hide file tree

Showing 3 changed files with 9 additions and 0 deletions.
diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
@@ -322,6 +322,9 @@ struct fpstate {
 	/* @user_xfeatures:	xfeatures valid in UABI buffers */
 	u64			user_xfeatures;
 
+	/* @xfd:		xfeatures disabled to trap userspace use. */
+	u64			xfd;
+
 	/* @is_valloc:		Indicator for dynamically allocated state */
 	unsigned int		is_valloc	: 1;
 

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
@@ -27,6 +27,7 @@
 
 #ifdef CONFIG_X86_64
 DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
+DEFINE_PER_CPU(u64, xfd_state);
 #endif
 
 /* The FPU state configuration data for kernel and user space */
@@ -409,6 +410,7 @@ static void __fpstate_reset(struct fpstate *fpstate)
 	fpstate->user_size	= fpu_user_cfg.default_size;
 	fpstate->xfeatures	= fpu_kernel_cfg.default_features;
 	fpstate->user_xfeatures	= fpu_user_cfg.default_features;
+	fpstate->xfd		= init_fpstate.xfd;
 }
 
 void fpstate_reset(struct fpu *fpu)

diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h
@@ -5,6 +5,10 @@
 #include <asm/cpufeature.h>
 #include <asm/fpu/xstate.h>
 
+#ifdef CONFIG_X86_64
+DECLARE_PER_CPU(u64, xfd_state);
+#endif
+
 static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)
 {
 	/*