From 9f79991d4186089e228274196413572cc000143b Mon Sep 17 00:00:00 2001 From: Jeremy Fitzhardinge Date: Tue, 16 Oct 2007 11:51:30 -0700 Subject: xen: deal with stale cr3 values when unpinning pagetables When a pagetable is no longer in use, it must be unpinned so that its pages can be freed. However, this is only possible if there are no stray uses of the pagetable. The code currently deals with all the usual cases, but there's a rare case where a vcpu is changing cr3, but is doing so lazily, and the change hasn't actually happened by the time the pagetable is unpinned, even though it appears to have been completed. This change adds a second per-cpu cr3 variable - xen_current_cr3 - which tracks the actual state of the vcpu cr3. It is only updated once the actual hypercall to set cr3 has been completed. Other processors wishing to unpin a pagetable can check other vcpu's xen_current_cr3 values to see if any cross-cpu IPIs are needed to clean things up. [ Stable folks: 2.6.23 bugfix ] Signed-off-by: Jeremy Fitzhardinge Cc: Stable Kernel --- arch/x86/xen/xen-ops.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/xen/xen-ops.h') diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index 3847eed0bb09..b02a909bfd4c 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -11,6 +11,7 @@ void xen_copy_trap_info(struct trap_info *traps); DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu); DECLARE_PER_CPU(unsigned long, xen_cr3); +DECLARE_PER_CPU(unsigned long, xen_current_cr3); extern struct start_info *xen_start_info; extern struct shared_info *HYPERVISOR_shared_info; -- cgit v1.2.3