update kernel to 5.10.198

hc

2024-01-03 2f7c68cb55ecb7331f2381deb497c27155f32faf

 kernel/arch/x86/kernel/fpu/core.c
..
..
@@ -25,17 +25,7 @@
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  */
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 union fpregs_state init_fpstate __read_mostly;
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-/*
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- * Track whether the kernel is using the FPU state
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- * currently.
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- *
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- * This flag is used:
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- *
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- *   - by IRQ context code to potentially use the FPU
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- *     if it's unused.
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- *
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- *   - to debug kernel_fpu_begin()/end() correctness
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- */
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+/* Track in-kernel FPU usage */
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 static DEFINE_PER_CPU(bool, in_kernel_fpu);
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 /*
..
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@@ -43,42 +33,37 @@
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  */
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 DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
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-static bool kernel_fpu_disabled(void)
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-{
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-	return this_cpu_read(in_kernel_fpu);
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-}
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-
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-static bool interrupted_kernel_fpu_idle(void)
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-{
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-	return !kernel_fpu_disabled();
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-}
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-
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-/*
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- * Were we in user mode (or vm86 mode) when we were
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- * interrupted?
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- *
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- * Doing kernel_fpu_begin/end() is ok if we are running
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- * in an interrupt context from user mode - we'll just
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- * save the FPU state as required.
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- */
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-static bool interrupted_user_mode(void)
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-{
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-	struct pt_regs *regs = get_irq_regs();
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-	return regs && user_mode(regs);
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-}
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-
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 /*
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  * Can we use the FPU in kernel mode with the
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  * whole "kernel_fpu_begin/end()" sequence?
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- *
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- * It's always ok in process context (ie "not interrupt")
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- * but it is sometimes ok even from an irq.
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  */
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 bool irq_fpu_usable(void)
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 {
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-	return !in_interrupt() ||
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-		interrupted_user_mode() ||
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-		interrupted_kernel_fpu_idle();
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+	if (WARN_ON_ONCE(in_nmi()))
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+		return false;
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+
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+	/* In kernel FPU usage already active? */
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+	if (this_cpu_read(in_kernel_fpu))
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+		return false;
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+
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+	/*
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+	 * When not in NMI or hard interrupt context, FPU can be used in:
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+	 *
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+	 * - Task context except from within fpregs_lock()'ed critical
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+	 *   regions.
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+	 *
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+	 * - Soft interrupt processing context which cannot happen
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+	 *   while in a fpregs_lock()'ed critical region.
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+	 */
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+	if (!in_irq())
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+		return true;
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+
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+	/*
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+	 * In hard interrupt context it's safe when soft interrupts
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+	 * are enabled, which means the interrupt did not hit in
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+	 * a fpregs_lock()'ed critical region.
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+	 */
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+	return !softirq_count();
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 }
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 EXPORT_SYMBOL(irq_fpu_usable);
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