pda.irqcount is used to test whether we need to switch to an irqstack or not. We can do without it, however, by testing %rsp directly: if it's already within the irqstack range we don't need to stacks.
This makes switching the nmi handler to use the irqstack easier. Signed-off-by: Avi Kivity <[email protected]> --- arch/x86/include/asm/pda.h | 2 +- arch/x86/kernel/asm-offsets_64.c | 1 - arch/x86/kernel/cpu/common.c | 1 - arch/x86/kernel/entry_64.S | 29 +++++++++++++---------------- 4 files changed, 14 insertions(+), 19 deletions(-) diff --git a/arch/x86/include/asm/pda.h b/arch/x86/include/asm/pda.h index 2fbfff8..2099610 100644 --- a/arch/x86/include/asm/pda.h +++ b/arch/x86/include/asm/pda.h @@ -14,7 +14,7 @@ struct x8664_pda { address */ unsigned long kernelstack; /* 16 top of kernel stack for current */ unsigned long oldrsp; /* 24 user rsp for system call */ - int irqcount; /* 32 Irq nesting counter. Starts -1 */ + int unused; /* 32 for rent */ unsigned int cpunumber; /* 36 Logical CPU number */ #ifdef CONFIG_CC_STACKPROTECTOR unsigned long stack_canary; /* 40 stack canary value */ diff --git a/arch/x86/kernel/asm-offsets_64.c b/arch/x86/kernel/asm-offsets_64.c index 7fcf63d..779d010 100644 --- a/arch/x86/kernel/asm-offsets_64.c +++ b/arch/x86/kernel/asm-offsets_64.c @@ -50,7 +50,6 @@ int main(void) ENTRY(kernelstack); ENTRY(oldrsp); ENTRY(pcurrent); - ENTRY(irqcount); ENTRY(cpunumber); ENTRY(irqstackptr); ENTRY(data_offset); diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 8563c51..6313d03 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -877,7 +877,6 @@ void __cpuinit pda_init(int cpu) mb(); pda->cpunumber = cpu; - pda->irqcount = -1; pda->kernelstack = (unsigned long)stack_thread_info() - PDA_STACKOFFSET + THREAD_SIZE; pda->active_mm = &init_mm; diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S index 8c882e1..245fecd 100644 --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -627,6 +627,15 @@ END(stub_rt_sigreturn) vector already pushed) */ #define XCPT_FRAME _frame ORIG_RAX + .macro enter_irqstack scratch + mov %gs:pda_irqstackptr, \scratch + sub %rsp, \scratch + cmp $IRQSTACKSIZE-64, \scratch + jbe 1234f + mov %gs:pda_irqstackptr, %rsp +1234: + .endm + /* * Interrupt entry/exit. * @@ -655,14 +664,7 @@ END(stub_rt_sigreturn) testl $3,CS(%rdi) je 1f SWAPGS - /* irqcount is used to check if a CPU is already on an interrupt - stack or not. While this is essentially redundant with preempt_count - it is a little cheaper to use a separate counter in the PDA - (short of moving irq_enter into assembly, which would be too - much work) */ -1: incl %gs:pda_irqcount - cmoveq %gs:pda_irqstackptr,%rsp - push %rbp # backlink for old unwinder +1: enter_irqstack %rax /* * We entered an interrupt context - irqs are off: */ @@ -677,7 +679,6 @@ ENTRY(common_interrupt) ret_from_intr: DISABLE_INTERRUPTS(CLBR_NONE) TRACE_IRQS_OFF - decl %gs:pda_irqcount leaveq CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET -8 @@ -1325,14 +1326,12 @@ ENTRY(call_softirq) CFI_REL_OFFSET rbp,0 mov %rsp,%rbp CFI_DEF_CFA_REGISTER rbp - incl %gs:pda_irqcount - cmove %gs:pda_irqstackptr,%rsp + enter_irqstack %rax push %rbp # backlink for old unwinder call __do_softirq leaveq CFI_DEF_CFA_REGISTER rsp CFI_ADJUST_CFA_OFFSET -8 - decl %gs:pda_irqcount ret CFI_ENDPROC ENDPROC(call_softirq) @@ -1369,15 +1368,13 @@ ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs) movq %rdi, %rsp # we don't return, adjust the stack frame CFI_ENDPROC CFI_DEFAULT_STACK -11: incl %gs:pda_irqcount - movq %rsp,%rbp +11: movq %rsp,%rbp CFI_DEF_CFA_REGISTER rbp - cmovzq %gs:pda_irqstackptr,%rsp + enter_irqstack %rax pushq %rbp # backlink for old unwinder call xen_evtchn_do_upcall popq %rsp CFI_DEF_CFA_REGISTER rsp - decl %gs:pda_irqcount jmp error_exit CFI_ENDPROC END(do_hypervisor_callback) -- 1.6.0.6 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
