From 88e957d6e47f1232ad15b21e54a44f1147ea8c1b Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Thu, 30 Jun 2016 17:56:37 +0200 Subject: [PATCH] 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 Signed-off-by: David Vrabel --- 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 2f4c3aa540eb..72cf06bf43f2 100644 --- a/arch/arm/xen/enlighten.c +++ b/arch/arm/xen/enlighten.c @@ -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, diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c index ee7d71ec762f..d093949c94e0 100644 --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -59,6 +59,7 @@ #include #include #include +#include #include #include #include @@ -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 355275bad2cf..c9c532d56623 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); -- 2.39.2