xen: introduce xen_vcpu_id mapping
It may happen that Xen's and Linux's ideas of vCPU id diverge. In
particular, when we crash on a secondary vCPU we may want to do kdump
and unlike plain kexec where we do migrate_to_reboot_cpu() we try
booting on the vCPU which crashed. This doesn't work very well for
PVHVM guests as we have a number of hypercalls where we pass vCPU id
as a parameter. These hypercalls either fail or do something
unexpected.
To solve the issue introduce percpu xen_vcpu_id mapping. ARM and PV
guests get direct mapping for now. Boot CPU for PVHVM guest gets its
id from CPUID. With secondary CPUs it is a bit more
trickier. Currently, we initialize IPI vectors before these CPUs boot
so we can't use CPUID. Use ACPI ids from MADT instead.
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 2f4c3aa..72cf06b 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -49,6 +49,10 @@
DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
static struct vcpu_info __percpu *xen_vcpu_info;
+/* Linux <-> Xen vCPU id mapping */
+DEFINE_PER_CPU(int, xen_vcpu_id) = -1;
+EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
+
/* These are unused until we support booting "pre-ballooned" */
unsigned long xen_released_pages;
struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
@@ -167,6 +171,9 @@
pr_info("Xen: initializing cpu%d\n", cpu);
vcpup = per_cpu_ptr(xen_vcpu_info, cpu);
+ /* Direct vCPU id mapping for ARM guests. */
+ per_cpu(xen_vcpu_id, cpu) = cpu;
+
info.mfn = virt_to_gfn(vcpup);
info.offset = xen_offset_in_page(vcpup);
@@ -388,6 +395,9 @@
if (xen_vcpu_info == NULL)
return -ENOMEM;
+ /* Direct vCPU id mapping for ARM guests. */
+ per_cpu(xen_vcpu_id, 0) = 0;
+
xen_auto_xlat_grant_frames.count = gnttab_max_grant_frames();
if (xen_xlate_map_ballooned_pages(&xen_auto_xlat_grant_frames.pfn,
&xen_auto_xlat_grant_frames.vaddr,