Commit 88e957d6 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by David Vrabel
Browse files

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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
parent 3e9e57fa

arch/arm/xen/enlighten.c

+10 −0
Original line number Diff line number Diff line
@@ -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,

arch/x86/xen/enlighten.c

+22 −1
Original line number Diff line number Diff line
@@ -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))

include/xen/xen-ops.h

+6 −0
Original line number Diff line number Diff line
@@ -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);

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