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xen: introduce xen_vcpu_id mapping

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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>
This commit is contained in:
Vitaly Kuznetsov
2016-06-30 17:56:37 +02:00
committed by David Vrabel
parent 3e9e57fad3
commit 88e957d6e4
3 changed files with 38 additions and 1 deletions
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10
arch/arm/xen/enlighten.c
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@@ -49,6 +49,10 @@ struct shared_info *HYPERVISOR_shared_info = (void *)&xen_dummy_shared_info;
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 @@ static void xen_percpu_init(void)
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 @@ static int __init xen_guest_init(void)
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,