x86/fpu/xstate: Use fpstate for os_xsave()

With variable feature sets XSAVE[S] requires to know the feature set for
which the buffer is valid. Retrieve it from fpstate.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20211013145323.025695590@linutronix.de

arch/x86/kernel/fpu/core.c

@@ -105,7 +105,7 @@ EXPORT_SYMBOL(irq_fpu_usable);
 void save_fpregs_to_fpstate(struct fpu *fpu)
 {
 	if (likely(use_xsave())) {
-		os_xsave(&fpu->fpstate->regs.xsave);
+		os_xsave(fpu->fpstate);
 
 		/*
 		 * AVX512 state is tracked here because its use is

arch/x86/kernel/fpu/signal.c

@@ -349,7 +349,6 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 	if (__copy_from_user(&env, buf, sizeof(env)))
 		return false;
 
-	fpregs = &fpu->fpstate->regs;
 	/*
 	 * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is
 	 * not modified on context switch and that the xstate is considered
@@ -367,13 +366,14 @@ static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx,
 		 * the right place in memory. It's ia32 mode. Shrug.
 		 */
 		if (xfeatures_mask_supervisor())
-			os_xsave(&fpregs->xsave);
+			os_xsave(fpu->fpstate);
 		set_thread_flag(TIF_NEED_FPU_LOAD);
 	}
 	__fpu_invalidate_fpregs_state(fpu);
 	__cpu_invalidate_fpregs_state();
 	fpregs_unlock();
 
+	fpregs = &fpu->fpstate->regs;
 	if (use_xsave() && !fx_only) {
 		if (copy_sigframe_from_user_to_xstate(&fpregs->xsave, buf_fx))
 			return false;

arch/x86/kernel/fpu/xstate.h

@@ -101,16 +101,16 @@ extern void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);
  * Uses either XSAVE or XSAVEOPT or XSAVES depending on the CPU features
  * and command line options. The choice is permanent until the next reboot.
  */
-static inline void os_xsave(struct xregs_state *xstate)
+static inline void os_xsave(struct fpstate *fpstate)
 {
-	u64 mask = xfeatures_mask_all;
+	u64 mask = fpstate->xfeatures;
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
 	int err;
 
 	WARN_ON_FPU(!alternatives_patched);
 
-	XSTATE_XSAVE(xstate, lmask, hmask, err);
+	XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);
 
 	/* We should never fault when copying to a kernel buffer: */
 	WARN_ON_FPU(err);