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x86/paravirt: split sysret and sysexit

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Don't conflate sysret and sysexit; they're different instructions with
different semantics, and may be in use at the same time (at least
within the same kernel, depending on whether its an Intel or AMD
system).

sysexit - just return to userspace, does no register restoration of
    any kind; must explicitly atomically enable interrupts.

sysret - reloads flags from r11, so no need to explicitly enable
    interrupts on 64-bit, responsible for restoring usermode %gs

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citirx.com>
Cc: xen-devel <xen-devel@lists.xensource.com>
Cc: Stephen Tweedie <sct@redhat.com>
Cc: Eduardo Habkost <ehabkost@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Jeremy Fitzhardinge
2008-06-25 00:19:26 -04:00
committed by Ingo Molnar
parent e04e0a630d
commit d75cd22fdd
11 changed files with 36 additions and 25 deletions
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4
include/asm-x86/irqflags.h
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@ -112,13 +112,13 @@ static inline unsigned long __raw_local_irq_save(void)
#ifdef CONFIG_X86_64
#define INTERRUPT_RETURN iretq
#define ENABLE_INTERRUPTS_SYSCALL_RET \
#define USERSP_SYSRET \
movq %gs:pda_oldrsp, %rsp; \
swapgs; \
sysretq;
#else
#define INTERRUPT_RETURN iret
#define ENABLE_INTERRUPTS_SYSCALL_RET sti; sysexit
#define ENABLE_INTERRUPTS_SYSEXIT sti; sysexit
#define GET_CR0_INTO_EAX movl %cr0, %eax
#endif