Commit 1f75619a authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86_misc_for_v6.9_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull misc x86 fixes from Borislav Petkov:

 - Fix a wrong check in the function reporting whether a CPU executes
   (or not) a NMI handler

 - Ratelimit unknown NMIs messages in order to not potentially slow down
   the machine

 - Other fixlets

* tag 'x86_misc_for_v6.9_rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/nmi: Fix the inverse "in NMI handler" check
  Documentation/maintainer-tip: Add C++ tail comments exception
  Documentation/maintainer-tip: Add Closes tag
  x86/nmi: Rate limit unknown NMI messages
  Documentation/kernel-parameters: Add spec_rstack_overflow to mitigations=off
parents 38b334fc d54e56f3

Documentation/admin-guide/kernel-parameters.txt

+1 −0
Original line number Diff line number Diff line
@@ -3395,6 +3395,7 @@ 
					       nospectre_v1 [X86,PPC]

					       nospectre_v2 [X86,PPC,S390,ARM64]

					       retbleed=off [X86]

					       spec_rstack_overflow=off [X86]

					       spec_store_bypass_disable=off [X86,PPC]

					       spectre_v2_user=off [X86]

					       srbds=off [X86,INTEL]

Documentation/process/maintainer-tip.rst

+32 −2
Original line number Diff line number Diff line
@@ -304,13 +304,15 @@ following tag ordering scheme: 


 - Reported-by: ``Reporter <reporter@mail>``



 - Closes: ``URL or Message-ID of the bug report this is fixing``



 - Originally-by: ``Original author <original-author@mail>``



 - Suggested-by: ``Suggester <suggester@mail>``



 - Co-developed-by: ``Co-author <co-author@mail>``



   Signed-off: ``Co-author <co-author@mail>``

   Signed-off-by: ``Co-author <co-author@mail>``



   Note, that Co-developed-by and Signed-off-by of the co-author(s) must

   come in pairs.
@@ -478,7 +480,7 @@ Multi-line comments:: 
	 * Larger multi-line comments should be split into paragraphs.

	 */



No tail comments:

No tail comments (see below):



  Please refrain from using tail comments. Tail comments disturb the

  reading flow in almost all contexts, but especially in code::
@@ -499,6 +501,34 @@ No tail comments: 
	/* This magic initialization needs a comment. Maybe not? */

	seed = MAGIC_CONSTANT;



  Use C++ style, tail comments when documenting structs in headers to

  achieve a more compact layout and better readability::



        // eax

        u32     x2apic_shift    :  5, // Number of bits to shift APIC ID right

                                      // for the topology ID at the next level

                                : 27; // Reserved

        // ebx

        u32     num_processors  : 16, // Number of processors at current level

                                : 16; // Reserved



  versus::



	/* eax */

	        /*

	         * Number of bits to shift APIC ID right for the topology ID

	         * at the next level

	         */

         u32     x2apic_shift    :  5,

		 /* Reserved */

				 : 27;



	/* ebx */

		/* Number of processors at current level */

	u32     num_processors  : 16,

		/* Reserved */

				: 16;



Comment the important things:



  Comments should be added where the operation is not obvious. Documenting

arch/x86/kernel/nmi.c

+4 −4
Original line number Diff line number Diff line
@@ -304,13 +304,13 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs) 


	__this_cpu_add(nmi_stats.unknown, 1);



	pr_emerg("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",

	pr_emerg_ratelimited("Uhhuh. NMI received for unknown reason %02x on CPU %d.\n",

			     reason, smp_processor_id());



	if (unknown_nmi_panic || panic_on_unrecovered_nmi)

		nmi_panic(regs, "NMI: Not continuing");



	pr_emerg("Dazed and confused, but trying to continue\n");

	pr_emerg_ratelimited("Dazed and confused, but trying to continue\n");

}

NOKPROBE_SYMBOL(unknown_nmi_error);
@@ -637,7 +637,7 @@ void nmi_backtrace_stall_check(const struct cpumask *btp) 
			msgp = nmi_check_stall_msg[idx];

			if (nsp->idt_ignored_snap != READ_ONCE(nsp->idt_ignored) && (idx & 0x1))

				modp = ", but OK because ignore_nmis was set";

			if (nmi_seq & ~0x1)

			if (nmi_seq & 0x1)

				msghp = " (CPU currently in NMI handler function)";

			else if (nsp->idt_nmi_seq_snap + 1 == nmi_seq)

				msghp = " (CPU exited one NMI handler function)";