Commit 8ef46a67 authored Mar 05, 2015 by Andy Lutomirski Committed by Ingo Molnar Mar 06, 2015

x86/asm/entry: Add this_cpu_sp0() to read sp0 for the current cpu



We currently store references to the top of the kernel stack in
multiple places: kernel_stack (with an offset) and
init_tss.x86_tss.sp0 (no offset).  The latter is defined by
hardware and is a clean canonical way to find the top of the
stack.  Add an accessor so we can start using it.

This needs minor paravirt tweaks.  On native, sp0 defines the
top of the kernel stack and is therefore always correct.  On Xen
and lguest, the hypervisor tracks the top of the stack, but we
want to start reading sp0 in the kernel.  Fixing this is simple:
just update our local copy of sp0 as well as the hypervisor's
copy on task switches.

Signed-off-by: Andy Lutomirski <luto@amacapital.net>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/8d675581859712bee09a055ed8f785d80dac1eca.1425611534.git.luto@amacapital.net


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 5eca7453

arch/x86/include/asm/processor.h

+5 −0

Original line number	Diff line number	Diff line
		@@ -564,6 +564,11 @@ static inline void native_swapgs(void)
		#endif
		}

		static inline unsigned long this_cpu_sp0(void)
		{
		return this_cpu_read_stable(init_tss.x86_tss.sp0);
		}

		#ifdef CONFIG_PARAVIRT
		#include <asm/paravirt.h>
		#else

arch/x86/kernel/process.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -38,6 +38,7 @@
		* on exact cacheline boundaries, to eliminate cacheline ping-pong.
		*/
		__visible DEFINE_PER_CPU_SHARED_ALIGNED(struct tss_struct, init_tss) = INIT_TSS;
		EXPORT_PER_CPU_SYMBOL_GPL(init_tss);

		#ifdef CONFIG_X86_64
		static DEFINE_PER_CPU(unsigned char, is_idle);

arch/x86/lguest/boot.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -1076,6 +1076,7 @@ static void lguest_load_sp0(struct tss_struct *tss,
		{
		lazy_hcall3(LHCALL_SET_STACK, __KERNEL_DS \| 0x1, thread->sp0,
		THREAD_SIZE / PAGE_SIZE);
		tss->x86_tss.sp0 = thread->sp0;
		}

		/* Let's just say, I wouldn't do debugging under a Guest. */

arch/x86/xen/enlighten.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -912,6 +912,7 @@ static void xen_load_sp0(struct tss_struct *tss,
		mcs = xen_mc_entry(0);
		MULTI_stack_switch(mcs.mc, __KERNEL_DS, thread->sp0);
		xen_mc_issue(PARAVIRT_LAZY_CPU);
		tss->x86_tss.sp0 = thread->sp0;
		}

		static void xen_set_iopl_mask(unsigned mask)

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