The following commit has been merged into the x86/fred branch of tip:
Commit-ID: 989b5cfaa7b6054f4e1bde914470ee091c23e6a5
Gitweb: https://git.kernel.org/tip/989b5cfaa7b6054f4e1bde914470ee091c23e6a5
Author: Xin Li (Intel) <xin@xxxxxxxxx>
AuthorDate: Tue, 09 Jul 2024 08:40:46 -07:00
Committer: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitterDate: Tue, 13 Aug 2024 21:59:21 +02:00
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: 3810da12710a ("x86/fred: Add a fred= cmdline param")
Reported-by: Hou Wenlong <houwenlong.hwl@xxxxxxxxxxxx>
Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Xin Li (Intel) <xin@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Link: https://lore.kernel.org/all/20240709154048.3543361-2-xin@xxxxxxxxx
---
arch/x86/kernel/cpu/common.c | 5 +++++
arch/x86/kernel/traps.c | 26 --------------------------
2 files changed, 5 insertions(+), 26 deletions(-)
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index d4e539d..10a5402 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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;
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index 4fa0b17..6afb41e 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -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();
|