Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758828AbYGHXU4 (ORCPT ); Tue, 8 Jul 2008 19:20:56 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1757614AbYGHXOu (ORCPT ); Tue, 8 Jul 2008 19:14:50 -0400 Received: from gw.goop.org ([64.81.55.164]:51204 "EHLO mail.goop.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756207AbYGHXOn (ORCPT ); Tue, 8 Jul 2008 19:14:43 -0400 Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [PATCH 27 of 55] xen64: add hypervisor callbacks for events, etc X-Mercurial-Node: 43817046e3f319aeec964d22144314e7a89a0c8f Message-Id: <43817046e3f319aeec96.1215554809@localhost> In-Reply-To: Date: Tue, 08 Jul 2008 15:06:49 -0700 From: Jeremy Fitzhardinge To: Ingo Molnar Cc: LKML , x86@kernel.org, Stephen Tweedie , Eduardo Habkost , Mark McLoughlin , x86@kernel.org Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3750 Lines: 117 Signed-off-by: Jeremy Fitzhardinge --- arch/x86/kernel/entry_64.S | 98 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 98 insertions(+) diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S --- a/arch/x86/kernel/entry_64.S +++ b/arch/x86/kernel/entry_64.S @@ -1312,3 +1312,101 @@ sysret CFI_ENDPROC ENDPROC(ignore_sysret) + +#ifdef CONFIG_XEN +ENTRY(xen_hypervisor_callback) + zeroentry xen_do_hypervisor_callback +END(xen_hypervisor_callback) + +/* +# A note on the "critical region" in our callback handler. +# We want to avoid stacking callback handlers due to events occurring +# during handling of the last event. To do this, we keep events disabled +# until we've done all processing. HOWEVER, we must enable events before +# popping the stack frame (can't be done atomically) and so it would still +# be possible to get enough handler activations to overflow the stack. +# Although unlikely, bugs of that kind are hard to track down, so we'd +# like to avoid the possibility. +# So, on entry to the handler we detect whether we interrupted an +# existing activation in its critical region -- if so, we pop the current +# activation and restart the handler using the previous one. +*/ +ENTRY(xen_do_hypervisor_callback) # do_hypervisor_callback(struct *pt_regs) + CFI_STARTPROC +/* Since we don't modify %rdi, evtchn_do_upall(struct *pt_regs) will + see the correct pointer to the 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 + CFI_DEF_CFA_REGISTER rbp + cmovzq %gs:pda_irqstackptr,%rsp + 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) + +/* +# Hypervisor uses this for application faults while it executes. +# We get here for two reasons: +# 1. Fault while reloading DS, ES, FS or GS +# 2. Fault while executing IRET +# Category 1 we do not need to fix up as Xen has already reloaded all segment +# registers that could be reloaded and zeroed the others. +# Category 2 we fix up by killing the current process. We cannot use the +# normal Linux return path in this case because if we use the IRET hypercall +# to pop the stack frame we end up in an infinite loop of failsafe callbacks. +# We distinguish between categories by comparing each saved segment register +# with its current contents: any discrepancy means we in category 1. +*/ +ENTRY(xen_failsafe_callback) +#if 1 + ud2a +#else + _frame (RIP-0x30) + CFI_REL_OFFSET rcx, 0 + CFI_REL_OFFSET r11, 8 + movw %ds,%cx + cmpw %cx,0x10(%rsp) + CFI_REMEMBER_STATE + jne 1f + movw %es,%cx + cmpw %cx,0x18(%rsp) + jne 1f + movw %fs,%cx + cmpw %cx,0x20(%rsp) + jne 1f + movw %gs,%cx + cmpw %cx,0x28(%rsp) + jne 1f + /* All segments match their saved values => Category 2 (Bad IRET). */ + movq (%rsp),%rcx + CFI_RESTORE rcx + movq 8(%rsp),%r11 + CFI_RESTORE r11 + addq $0x30,%rsp + CFI_ADJUST_CFA_OFFSET -0x30 + movq $11,%rdi /* SIGSEGV */ + jmp do_exit + CFI_RESTORE_STATE +1: /* Segment mismatch => Category 1 (Bad segment). Retry the IRET. */ + movq (%rsp),%rcx + CFI_RESTORE rcx + movq 8(%rsp),%r11 + CFI_RESTORE r11 + addq $0x30,%rsp + CFI_ADJUST_CFA_OFFSET -0x30 + pushq $0 + CFI_ADJUST_CFA_OFFSET 8 + SAVE_ALL + jmp error_exit + CFI_ENDPROC +#endif +END(xen_failsafe_callback) + +#endif /* CONFIG_XEN */ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/