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Date: Thu, 30 Jun 2016 17:56:37 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: xen-devel@...ts.xenproject.org
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
Stefano Stabellini <sstabellini@...nel.org>,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
David Vrabel <david.vrabel@...rix.com>,
Juergen Gross <jgross@...e.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>,
"H. Peter Anvin" <hpa@...or.com>,
"Jan Beulich" <JBeulich@...e.com>,
Andrew Cooper <andrew.cooper3@...rix.com>
Subject: [PATCH linux v2 3/9] 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@...hat.com>
---
Changes since v1:
- Introduce xen_vcpu_nr() helper [David Vrabel]
- Use ACPI ids instead of vLAPIC ids /2 [Andrew Cooper, Jan Beulich]
---
arch/arm/xen/enlighten.c | 10 ++++++++++
arch/x86/xen/enlighten.c | 23 ++++++++++++++++++++++-
include/xen/xen-ops.h | 6 ++++++
3 files changed, 38 insertions(+), 1 deletion(-)
diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
index 75cd734..1678446 100644
--- a/arch/arm/xen/enlighten.c
+++ b/arch/arm/xen/enlighten.c
@@ -46,6 +46,10 @@ 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;
@@ -179,6 +183,9 @@ 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);
@@ -328,6 +335,9 @@ 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;
+
if (gnttab_setup_auto_xlat_frames(grant_frames)) {
free_percpu(xen_vcpu_info);
return -ENOMEM;
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 760789a..ff01f3d 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -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))
diff --git a/include/xen/xen-ops.h b/include/xen/xen-ops.h
index 86abe07..a4926f1 100644
--- a/include/xen/xen-ops.h
+++ b/include/xen/xen-ops.h
@@ -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);
--
2.5.5
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