x86/alternatives, x86/fpu: Add 'alternatives_patched' debug flag and use it in xsave_state()
We'd like to use xsave_state() earlier, but its SYSTEM_BOOTING check
is too imprecise.
The real condition that xsave_state() would like to check is whether
alternative XSAVE instructions were patched into the kernel image
already.
Add such a (read-mostly) debug flag and use it in xsave_state().
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index ba32af0..7bfc85b 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -52,6 +52,12 @@
u8 padlen; /* length of build-time padding */
} __packed;
+/*
+ * Debug flag that can be tested to see whether alternative
+ * instructions were patched in already:
+ */
+extern int alternatives_patched;
+
extern void alternative_instructions(void);
extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 31a002a..ab2c507 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -119,7 +119,7 @@
u32 hmask = mask >> 32;
int err = 0;
- WARN_ON(system_state == SYSTEM_BOOTING);
+ WARN_ON(!alternatives_patched);
/*
* If xsaves is enabled, xsaves replaces xsaveopt because
diff --git a/arch/x86/kernel/alternative.c b/arch/x86/kernel/alternative.c
index aef6531..7fe0972 100644
--- a/arch/x86/kernel/alternative.c
+++ b/arch/x86/kernel/alternative.c
@@ -21,6 +21,10 @@
#include <asm/io.h>
#include <asm/fixmap.h>
+int __read_mostly alternatives_patched;
+
+EXPORT_SYMBOL_GPL(alternatives_patched);
+
#define MAX_PATCH_LEN (255-1)
static int __initdata_or_module debug_alternative;
@@ -627,6 +631,7 @@
apply_paravirt(__parainstructions, __parainstructions_end);
restart_nmi();
+ alternatives_patched = 1;
}
/**