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

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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: 3810da1271 ("x86/fred: Add a fred= cmdline param")
Reported-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Xin Li (Intel) <xin@zytor.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20240709154048.3543361-2-xin@zytor.com
This commit is contained in:
Xin Li (Intel) 2024-07-09 08:40:46 -07:00 committed by Thomas Gleixner
parent 7c626ce4ba
commit 989b5cfaa7
2 changed files with 5 additions and 26 deletions
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5
arch/x86/kernel/cpu/common.c
View File

@ -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;

26
arch/x86/kernel/traps.c
View File

@ -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();