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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>
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/arm/xen/enlighten.c
View File

@ -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,

23
arch/x86/xen/enlighten.c
View File

@ -59,6 +59,7 @@
#include <asm/xen/pci.h>
#include <asm/xen/hypercall.h>
#include <asm/xen/hypervisor.h>
#include <asm/xen/cpuid.h>
#include <asm/fixmap.h>
#include <asm/processor.h>
#include <asm/proto.h>
@ -118,6 +119,10 @@ DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
*/
DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);
/* Linux <-> Xen vCPU id mapping */
DEFINE_PER_CPU(int, xen_vcpu_id) = -1;
EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
enum xen_domain_type xen_domain_type = XEN_NATIVE;
EXPORT_SYMBOL_GPL(xen_domain_type);
@ -1137,8 +1142,11 @@ void xen_setup_vcpu_info_placement(void)
{
int cpu;
for_each_possible_cpu(cpu)
for_each_possible_cpu(cpu) {
/* Set up direct vCPU id mapping for PV guests. */
per_cpu(xen_vcpu_id, cpu) = cpu;
xen_vcpu_setup(cpu);
}
/* xen_vcpu_setup managed to place the vcpu_info within the
* percpu area for all cpus, so make use of it. Note that for
@ -1729,6 +1737,9 @@ asmlinkage __visible void __init xen_start_kernel(void)
#endif
xen_raw_console_write("about to get started...\n");
/* Let's presume PV guests always boot on vCPU with id 0. */
per_cpu(xen_vcpu_id, 0) = 0;
xen_setup_runstate_info(0);
xen_efi_init();
@ -1797,6 +1808,12 @@ static void __init init_hvm_pv_info(void)
xen_setup_features();
cpuid(base + 4, &eax, &ebx, &ecx, &edx);
if (eax & XEN_HVM_CPUID_VCPU_ID_PRESENT)
this_cpu_write(xen_vcpu_id, ebx);
else
this_cpu_write(xen_vcpu_id, smp_processor_id());
pv_info.name = "Xen HVM";
xen_domain_type = XEN_HVM_DOMAIN;
@ -1808,6 +1825,10 @@ static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
int cpu = (long)hcpu;
switch (action) {
case CPU_UP_PREPARE:
if (cpu_acpi_id(cpu) != U32_MAX)
per_cpu(xen_vcpu_id, cpu) = cpu_acpi_id(cpu);
else
per_cpu(xen_vcpu_id, cpu) = cpu;
xen_vcpu_setup(cpu);
if (xen_have_vector_callback) {
if (xen_feature(XENFEAT_hvm_safe_pvclock))

6
include/xen/xen-ops.h
View File

@ -9,6 +9,12 @@
DECLARE_PER_CPU(struct vcpu_info *, xen_vcpu);
DECLARE_PER_CPU(int, xen_vcpu_id);
static inline int xen_vcpu_nr(int cpu)
{
return per_cpu(xen_vcpu_id, cpu);
}
void xen_arch_pre_suspend(void);
void xen_arch_post_suspend(int suspend_cancelled);