Commit 989b5cfa authored by Xin Li (Intel)'s avatar Xin Li (Intel) Committed by Thomas Gleixner
Browse files

x86/fred: Parse cmdline param "fred=" in cpu_parse_early_param() 



Depending on whether FRED is enabled, sysvec_install() installs a system
interrupt handler into either into FRED's system vector dispatch table or
into the IDT.

However FRED can be disabled later in trap_init(), after sysvec_install()
has been invoked already; e.g., the HYPERVISOR_CALLBACK_VECTOR handler is
registered with sysvec_install() in kvm_guest_init(), which is called in
setup_arch() but way before trap_init().

IOW, there is a gap between FRED is available and available but disabled.
As a result, when FRED is available but disabled, early sysvec_install()
invocations fail to install the IDT handler resulting in spurious
interrupts.

Fix it by parsing cmdline param "fred=" in cpu_parse_early_param() to
ensure that FRED is disabled before the first sysvec_install() incovations.

Fixes: 3810da12 ("x86/fred: Add a fred= cmdline param")
Reported-by: default avatarHou Wenlong <houwenlong.hwl@antgroup.com>
Suggested-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarXin Li (Intel) <xin@zytor.com>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-2-xin@zytor.com
parent 7c626ce4

arch/x86/kernel/cpu/common.c

+5 −0
Original line number Diff line number Diff line
@@ -1510,6 +1510,11 @@ static void __init cpu_parse_early_param(void) 
	if (cmdline_find_option_bool(boot_command_line, "nousershstk"))

		setup_clear_cpu_cap(X86_FEATURE_USER_SHSTK);



	/* Minimize the gap between FRED is available and available but disabled. */

	arglen = cmdline_find_option(boot_command_line, "fred", arg, sizeof(arg));

	if (arglen != 2 || strncmp(arg, "on", 2))

		setup_clear_cpu_cap(X86_FEATURE_FRED);



	arglen = cmdline_find_option(boot_command_line, "clearcpuid", arg, sizeof(arg));

	if (arglen <= 0)

		return;

arch/x86/kernel/traps.c

+0 −26
Original line number Diff line number Diff line
@@ -1402,34 +1402,8 @@ DEFINE_IDTENTRY_SW(iret_error) 
}

#endif



/* Do not enable FRED by default yet. */

static bool enable_fred __ro_after_init = false;



#ifdef CONFIG_X86_FRED

static int __init fred_setup(char *str)

{

	if (!str)

		return -EINVAL;



	if (!cpu_feature_enabled(X86_FEATURE_FRED))

		return 0;



	if (!strcmp(str, "on"))

		enable_fred = true;

	else if (!strcmp(str, "off"))

		enable_fred = false;

	else

		pr_warn("invalid FRED option: 'fred=%s'\n", str);

	return 0;

}

early_param("fred", fred_setup);

#endif



void __init trap_init(void)

{

	if (cpu_feature_enabled(X86_FEATURE_FRED) && !enable_fred)

		setup_clear_cpu_cap(X86_FEATURE_FRED);



	/* Init cpu_entry_area before IST entries are set up */

	setup_cpu_entry_areas();