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Subject[PATCH 176/208] x86/alternatives, x86/fpu: Add 'alternatives_patched' debug flag and use it in xsave_state()
Date
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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
arch/x86/include/asm/alternative.h | 6 ++++++
arch/x86/include/asm/fpu/xstate.h | 2 +-
arch/x86/kernel/alternative.c | 5 +++++
3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/alternative.h b/arch/x86/include/asm/alternative.h
index ba32af062f61..7bfc85bbb8ff 100644
--- a/arch/x86/include/asm/alternative.h
+++ b/arch/x86/include/asm/alternative.h
@@ -52,6 +52,12 @@ struct alt_instr {
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 31a002ad5aeb..ab2c507b58b6 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -119,7 +119,7 @@ static inline int xsave_state(struct xsave_struct *fx)
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 aef653193160..7fe097235376 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 @@ void __init alternative_instructions(void)
apply_paravirt(__parainstructions, __parainstructions_end);

restart_nmi();
+ alternatives_patched = 1;
}

/**
--
2.1.0


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