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

diff --git a/arch/x86/include/asm/fpu/types.h b/arch/x86/include/asm/fpu/types.h
index 595122fcaf513a50dbe3228dae9fe19039899e03..b1897638d68dd0eec61863418ea5afbd17078640 100644 (file)
--- 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
index 3349068cef7de22e8ae706ac7235cb539ad5a078..3b72cddf990d6845585d928456f894130f852edd 100644 (file)
--- 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
index 4ce1dc030f38489de9b7ccc7c85f3a8d057ac717..32a4dee4de3b43393f9855367bc91c11a35eb5ef 100644 (file)
--- 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)
 {
        /*