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authorPaul Mackerras <paulus@samba.org>2012-02-03 00:54:17 +0000
committerAvi Kivity <avi@redhat.com>2012-04-08 14:01:20 +0300
commitf0888f70151c7f53de2b45ee20ff1905837943e8 (patch)
tree80b7e133e681a2b4e4255a8fa747711da4c59211 /arch/powerpc/include/asm/kvm_book3s_asm.h
parentf6127716c346c73ab1513edee53231800188c5ba (diff)
KVM: PPC: Book3S HV: Make secondary threads more robust against stray IPIs
Currently on POWER7, if we are running the guest on a core and we don't need all the hardware threads, we do nothing to ensure that the unused threads aren't executing in the kernel (other than checking that they are offline). We just assume they're napping and we don't do anything to stop them trying to enter the kernel while the guest is running. This means that a stray IPI can wake up the hardware thread and it will then try to enter the kernel, but since the core is in guest context, it will execute code from the guest in hypervisor mode once it turns the MMU on, which tends to lead to crashes or hangs in the host. This fixes the problem by adding two new one-byte flags in the kvmppc_host_state structure in the PACA which are used to interlock between the primary thread and the unused secondary threads when entering the guest. With these flags, the primary thread can ensure that the unused secondaries are not already in kernel mode (i.e. handling a stray IPI) and then indicate that they should not try to enter the kernel if they do get woken for any reason. Instead they will go into KVM code, find that there is no vcpu to run, acknowledge and clear the IPI and go back to nap mode. Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Alexander Graf <agraf@suse.de> Signed-off-by: Avi Kivity <avi@redhat.com>
Diffstat (limited to 'arch/powerpc/include/asm/kvm_book3s_asm.h')
-rw-r--r--arch/powerpc/include/asm/kvm_book3s_asm.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/kvm_book3s_asm.h b/arch/powerpc/include/asm/kvm_book3s_asm.h
index 1f2f5b6156bd..88609b23b775 100644
--- a/arch/powerpc/include/asm/kvm_book3s_asm.h
+++ b/arch/powerpc/include/asm/kvm_book3s_asm.h
@@ -79,6 +79,9 @@ struct kvmppc_host_state {
u8 napping;
#ifdef CONFIG_KVM_BOOK3S_64_HV
+ u8 hwthread_req;
+ u8 hwthread_state;
+
struct kvm_vcpu *kvm_vcpu;
struct kvmppc_vcore *kvm_vcore;
unsigned long xics_phys;
@@ -122,4 +125,9 @@ struct kvmppc_book3s_shadow_vcpu {
#endif /*__ASSEMBLY__ */
+/* Values for kvm_state */
+#define KVM_HWTHREAD_IN_KERNEL 0
+#define KVM_HWTHREAD_IN_NAP 1
+#define KVM_HWTHREAD_IN_KVM 2
+
#endif /* __ASM_KVM_BOOK3S_ASM_H__ */

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