Vitaly Kuznetsov <vkuzn...@redhat.com> writes:
> Andrew Cooper <andrew.coop...@citrix.com> writes:
>
>> On 29/06/16 13:16, Vitaly Kuznetsov wrote:
>>> Andrew Cooper <andrew.coop...@citrix.com> writes:
>>>
>>>> On 28/06/16 17:47, Vitaly Kuznetsov wrote:
>>>>> @@ -1808,6 +1822,8 @@ static int xen_hvm_cpu_notify(struct notifier_block
>>>>> *self, unsigned long action,
>>>>> int cpu = (long)hcpu;
>>>>> switch (action) {
>>>>> case CPU_UP_PREPARE:
>>>>> + /* vLAPIC_ID == Xen's vCPU_ID * 2 for HVM guests */
>>>>> + per_cpu(xen_vcpu_id, cpu) = cpu_physical_id(cpu) / 2;
>>>> Please do not assume or propagate this brokenness. It is incorrect in
>>>> the general case, and I will be fixing in the hypervisor in due course.
>>>>
>>>> Always read the APIC_ID from the LAPIC, per regular hardware.
>>> (I'm probbaly missing something important - please bear with me)
>>>
>>> The problem here is that I need to get _other_ CPU's id before any code
>>> is executed on that CPU (or, at least, this is the current state of
>>> affairs if you look at xen_hvm_cpu_up()) so I can't use CPUID/do MSR
>>> reads/... The only option I see here is to rely on ACPI (MADT) data
>>> which is stored in x86_cpu_to_apicid (and that's what cpu_physical_id()
>>> gives us). MADT also has processor id which connects it to DSDT but I'm
>>> not sure Linux keeps this data. But this is something fixable I guess.
>>
>> Hmm yes - that is a tricky issue.
>>
>> It is not safe or correct to assume that xen_vcpu_id is APICID / 2.
>>
>> This is currently the case for most modern versions of Xen, but isn't
>> the case for older versions, and won't be the case in the future when I
>> (or someone else) fixes topology representation for guests.
>>
>> For this to work, we need one or more of:
>>
>> 1) to provide the guest a full mapping from APIC_ID to vcpu id at boot
>> time.
>
> So can we rely on ACPI data? Especially on MADT and processor ids there?
> I think we can always guarantee that processor ids there match vCPU
> ids. If yes I can try saving this data when we parse MADT.
>
To explain better what I'm trying to suggest here please take a look at
the attached patch. If we can guarantee long term that ACPI id always
equals to Xen's idea of vCPU id this is probably the easiest way.
--
Vitaly
>From 7c9cd25bdcd3e6ee866aa49550c9a4160194c3ba Mon Sep 17 00:00:00 2001
From: Vitaly Kuznetsov <vkuzn...@redhat.com>
Date: Wed, 29 Jun 2016 18:13:01 +0200
Subject: [PATCH RFC/WIP] x86/acpi: store APIC ids for future usage (+use it in
xen_hvm_cpu_notify)
Signed-off-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
---
arch/x86/include/asm/smp.h | 1 +
arch/x86/kernel/acpi/boot.c | 18 ++++++++++++++----
arch/x86/kernel/setup_percpu.c | 3 +++
arch/x86/xen/enlighten.c | 8 ++++++--
4 files changed, 24 insertions(+), 6 deletions(-)
diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
index 66b0573..c68b56a 100644
--- a/arch/x86/include/asm/smp.h
+++ b/arch/x86/include/asm/smp.h
@@ -33,6 +33,7 @@ static inline struct cpumask *cpu_llc_shared_mask(int cpu)
}
DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid);
+DECLARE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_acpiid);
DECLARE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_bios_cpu_apicid);
#if defined(CONFIG_X86_LOCAL_APIC) && defined(CONFIG_X86_32)
DECLARE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_logical_apicid);
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index 9414f84..3bbf0ab 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -110,6 +110,9 @@ static u32 isa_irq_to_gsi[NR_IRQS_LEGACY] __read_mostly = {
#define ACPI_INVALID_GSI INT_MIN
+DEFINE_EARLY_PER_CPU_READ_MOSTLY(int, x86_cpu_to_acpiid, -1);
+EXPORT_EARLY_PER_CPU_SYMBOL(x86_cpu_to_acpiid);
+
/*
* This is just a simple wrapper around early_ioremap(),
* with sanity checks for phys == 0 and size == 0.
@@ -165,9 +168,10 @@ static int __init acpi_parse_madt(struct acpi_table_header *table)
*
* Returns the logic cpu number which maps to the local apic
*/
-static int acpi_register_lapic(int id, u8 enabled)
+static int acpi_register_lapic(int id, int acpiid, u8 enabled)
{
unsigned int ver = 0;
+ int cpu;
if (id >= MAX_LOCAL_APIC) {
printk(KERN_INFO PREFIX "skipped apicid that is too big\n");
@@ -182,7 +186,11 @@ static int acpi_register_lapic(int id, u8 enabled)
if (boot_cpu_physical_apicid != -1U)
ver = apic_version[boot_cpu_physical_apicid];
- return generic_processor_info(id, ver);
+ cpu = generic_processor_info(id, ver);
+ if (cpu >= 0)
+ early_per_cpu(x86_cpu_to_acpiid, cpu) = acpiid;
+
+ return cpu;
}
static int __init
@@ -212,7 +220,7 @@ acpi_parse_x2apic(struct acpi_subtable_header *header, const unsigned long end)
if (!apic->apic_id_valid(apic_id) && enabled)
printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
else
- acpi_register_lapic(apic_id, enabled);
+ acpi_register_lapic(apic_id, processor->uid, enabled);
#else
printk(KERN_WARNING PREFIX "x2apic entry ignored\n");
#endif
@@ -240,6 +248,7 @@ acpi_parse_lapic(struct acpi_subtable_header * header, const unsigned long end)
* when we use CPU hotplug.
*/
acpi_register_lapic(processor->id, /* APIC ID */
+ processor->processor_id, /* ACPI ID */
processor->lapic_flags & ACPI_MADT_ENABLED);
return 0;
@@ -258,6 +267,7 @@ acpi_parse_sapic(struct acpi_subtable_header *header, const unsigned long end)
acpi_table_print_madt_entry(header);
acpi_register_lapic((processor->id << 8) | processor->eid,/* APIC ID */
+ processor->uid, /* ACPI ID */
processor->lapic_flags & ACPI_MADT_ENABLED);
return 0;
@@ -714,7 +724,7 @@ int acpi_map_cpu(acpi_handle handle, phys_cpuid_t physid, int *pcpu)
{
int cpu;
- cpu = acpi_register_lapic(physid, ACPI_MADT_ENABLED);
+ cpu = acpi_register_lapic(physid, -1, ACPI_MADT_ENABLED);
if (cpu < 0) {
pr_info(PREFIX "Unable to map lapic to logical cpu number\n");
return cpu;
diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index e4fcb87..7a40e06 100644
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -236,6 +236,8 @@ void __init setup_per_cpu_areas(void)
early_per_cpu_map(x86_cpu_to_apicid, cpu);
per_cpu(x86_bios_cpu_apicid, cpu) =
early_per_cpu_map(x86_bios_cpu_apicid, cpu);
+ per_cpu(x86_cpu_to_acpiid, cpu) =
+ early_per_cpu_map(x86_cpu_to_acpiid, cpu);
#endif
#ifdef CONFIG_X86_32
per_cpu(x86_cpu_to_logical_apicid, cpu) =
@@ -271,6 +273,7 @@ void __init setup_per_cpu_areas(void)
#ifdef CONFIG_X86_LOCAL_APIC
early_per_cpu_ptr(x86_cpu_to_apicid) = NULL;
early_per_cpu_ptr(x86_bios_cpu_apicid) = NULL;
+ early_per_cpu_ptr(x86_cpu_to_acpiid) = NULL;
#endif
#ifdef CONFIG_X86_32
early_per_cpu_ptr(x86_cpu_to_logical_apicid) = NULL;
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 0be29a0..8ae4871 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1825,10 +1825,14 @@ static int xen_hvm_cpu_notify(struct notifier_block *self, unsigned long action,
void *hcpu)
{
int cpu = (long)hcpu;
+ int acpiid = per_cpu(x86_cpu_to_acpiid, cpu);
+
switch (action) {
case CPU_UP_PREPARE:
- /* vLAPIC_ID == Xen's vCPU_ID * 2 for HVM guests */
- per_cpu(xen_vcpu_id, cpu) = cpu_physical_id(cpu) / 2;
+ if (acpiid != -1)
+ per_cpu(xen_vcpu_id, cpu) = acpiid;
+ else
+ per_cpu(xen_vcpu_id, cpu) = cpu;
xen_vcpu_setup(cpu);
if (xen_have_vector_callback) {
if (xen_feature(XENFEAT_hvm_safe_pvclock))
--
2.5.5
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
