Commit 1cff92d8 authored by H. Peter Anvin's avatar H. Peter Anvin
Browse files

x86, xsave: Make xstate_enable_boot_cpu() __init, protect on CPU 0 



xstate_enable_boot_cpu() is, as the name implies, only used on the
boot CPU; furthermore, it invokes alloc_bootmem(), which is __init;
hence it needs to be tagged __init rather than __cpuinit.

Furthermore, it is *not* safe in the long run to rely on CPU 0 only
coming online during the early boot -- at some point we're going to
support offlining (and re-onlining) the boot CPU, and at that point we
must not call xstate_enable_boot_cpu() again.

The code is a fair bit more obscure than one would like, because the
__ref overrides aren't quite powerful enough.

Signed-off-by: default avatarH. Peter Anvin <hpa@linux.intel.com>
Acked-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Cc: Robert Richter <robert.richter@amd.com>
LKML-Reference: <4C476236.1020302@zytor.com>
parent 4995b9db

arch/x86/kernel/xsave.c

+17 −11
Original line number Diff line number Diff line
@@ -360,10 +360,10 @@ unsigned int sig_xstate_size = sizeof(struct _fpstate); 
/*

 * Enable the extended processor state save/restore feature

 */

static inline void xstate_enable(u64 mask)

static inline void xstate_enable(void)

{

	set_in_cr4(X86_CR4_OSXSAVE);

	xsetbv(XCR_XFEATURE_ENABLED_MASK, mask);

	xsetbv(XCR_XFEATURE_ENABLED_MASK, pcntxt_mask);

}



/*
@@ -421,7 +421,7 @@ static void __init setup_xstate_init(void) 
/*

 * Enable and initialize the xsave feature.

 */

static void __cpuinit xstate_enable_boot_cpu(void)

static void __init xstate_enable_boot_cpu(void)

{

	unsigned int eax, ebx, ecx, edx;
@@ -444,7 +444,7 @@ static void __cpuinit xstate_enable_boot_cpu(void) 
	 */

	pcntxt_mask = pcntxt_mask & XCNTXT_MASK;



	xstate_enable(pcntxt_mask);

	xstate_enable();



	/*

	 * Recompute the context size for enabled features
@@ -462,16 +462,22 @@ static void __cpuinit xstate_enable_boot_cpu(void) 
	       pcntxt_mask, xstate_size);

}



/*

 * For the very first instance, this calls xstate_enable_boot_cpu();

 * for all subsequent instances, this calls xstate_enable().

 *

 * This is somewhat obfuscated due to the lack of powerful enough

 * overrides for the section checks.

 */

void __cpuinit xsave_init(void)

{

	static __refdata void (*next_func)(void) = xstate_enable_boot_cpu;

	void (*this_func)(void);



	if (!cpu_has_xsave)

		return;



	/*

	 * Boot processor to setup the FP and extended state context info.

	 */

	if (!smp_processor_id())

		xstate_enable_boot_cpu();

	else

		xstate_enable(pcntxt_mask);

	this_func = next_func;

	next_func = xstate_enable;

	this_func();

}

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