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Subject[PATCH linux 3/8] x86/xen: use xen_vcpu_id mapping for HYPERVISOR_vcpu_op
Date
HYPERVISOR_vcpu_op passes Linux's idea of vCPU id as a parameter while
Xen's idea is expected. In some cases these ideas diverge so we need to
do remapping.

There is an issue, however. PV guests do VCPUOP_is_up very early
(see xen_fill_possible_map() and xen_filter_cpu_maps()) when we don't have
perpu areas initialized. While it could be solved with switching to
early_percpu for xen_vcpu_id I think it's not worth it: PV guests will
probably never get to the point where their idea of vCPU id diverges from
Xen's.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
arch/x86/include/asm/xen/hypercall.h | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/xen/hypercall.h b/arch/x86/include/asm/xen/hypercall.h
index a12a047..20750c8 100644
--- a/arch/x86/include/asm/xen/hypercall.h
+++ b/arch/x86/include/asm/xen/hypercall.h
@@ -49,6 +49,7 @@
#include <xen/interface/physdev.h>
#include <xen/interface/platform.h>
#include <xen/interface/xen-mca.h>
+#include <xen/xen-ops.h>

/*
* The hypercall asms have to meet several constraints:
@@ -422,7 +423,15 @@ HYPERVISOR_vm_assist(unsigned int cmd, unsigned int type)
static inline int
HYPERVISOR_vcpu_op(int cmd, int vcpuid, void *extra_args)
{
- return _hypercall3(int, vcpu_op, cmd, vcpuid, extra_args);
+ /*
+ * PV guests call HYPERVISOR_vcpu_op before percpu areas are
+ * initialized. As we always use direct mapping for vCPU ids
+ * for them we can simply use Linux vcpuid here.
+ */
+ return _hypercall3(int, vcpu_op, cmd,
+ per_cpu(xen_vcpu_id, vcpuid) != -1 ?
+ per_cpu(xen_vcpu_id, vcpuid) : vcpuid,
+ extra_args);
}

#ifdef CONFIG_X86_64
--
2.5.5
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