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SubjectRE: [PATCH 2/5] X86: Hyper-V: Enable IPI enlightenments
Date
> -----Original Message-----
> From: kys@linuxonhyperv.com <kys@linuxonhyperv.com>
> Sent: Wednesday, April 25, 2018 11:13 AM
> To: x86@kernel.org; gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com; jasowang@redhat.com;
> tglx@linutronix.de; hpa@zytor.com; Stephen Hemminger <sthemmin@microsoft.com>;
> Michael Kelley (EOSG) <Michael.H.Kelley@microsoft.com>; vkuznets@redhat.com
> Cc: KY Srinivasan <kys@microsoft.com>
> Subject: [PATCH 2/5] X86: Hyper-V: Enable IPI enlightenments
>
> From: "K. Y. Srinivasan" <kys@microsoft.com>
>
> Hyper-V supports hypercalls to implement IPI; use them.
>
> Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> ---
> arch/x86/hyperv/hv_apic.c | 125 +++++++++++++++++++++++++++++++++++++
> arch/x86/hyperv/hv_init.c | 17 +++++
> arch/x86/include/asm/hyperv-tlfs.h | 9 +++
> arch/x86/include/asm/mshyperv.h | 1 +
> 4 files changed, 152 insertions(+)
>
> diff --git a/arch/x86/hyperv/hv_apic.c b/arch/x86/hyperv/hv_apic.c
> index e0a5b36208fc..7f3322ecfb01 100644
> --- a/arch/x86/hyperv/hv_apic.c
> +++ b/arch/x86/hyperv/hv_apic.c
> @@ -30,6 +30,14 @@
> #include <linux/slab.h>
> #include <linux/cpuhotplug.h>
>
> +struct ipi_arg_non_ex {
> + u32 vector;
> + u32 reserved;
> + u64 cpu_mask;
> +};

I think we'd like to put structures like this, which are defined in the
Hyper-V Top Level Functional Spec, in hyperv-tlfs.h. Also, the 5.0b
version of the TLFS, which is latest, shows this structure on page 100:

u32 vector;
u8 targetvtl;
u8 reserved[3];
u64 cpu_mask;

> +
> +static struct apic orig_apic;
> +
> static u64 hv_apic_icr_read(void)
> {
> u64 reg_val;
> @@ -85,8 +93,125 @@ static void hv_apic_eoi_write(u32 reg, u32 val)
> wrmsr(HV_X64_MSR_EOI, val, 0);
> }
>
> +/*
> + * IPI implementation on Hyper-V.
> + */
> +
> +static int __send_ipi_mask(const struct cpumask *mask, int vector)
> +{
> + int cur_cpu, vcpu;
> + struct ipi_arg_non_ex **arg;
> + struct ipi_arg_non_ex *ipi_arg;
> + int ret = 1;
> + unsigned long flags;
> +
> + if (cpumask_empty(mask))
> + return 0;
> +
> + if (!hv_hypercall_pg)
> + return ret;
> +
> + if ((vector < HV_IPI_LOW_VECTOR) || (vector > HV_IPI_HIGH_VECTOR))
> + return ret;
> +
> + local_irq_save(flags);
> + arg = (struct ipi_arg_non_ex **)this_cpu_ptr(hyperv_pcpu_input_arg);
> +
> + ipi_arg = *arg;
> + if (unlikely(!ipi_arg))
> + goto ipi_mask_done;
> +
> +
> + ipi_arg->vector = vector;
> + ipi_arg->reserved = 0;
> + ipi_arg->cpu_mask = 0;
> +
> + for_each_cpu(cur_cpu, mask) {
> + vcpu = hv_cpu_number_to_vp_number(cur_cpu);
> + if (vcpu >= 64)
> + goto ipi_mask_done;
> +
> + __set_bit(vcpu, (unsigned long *)&ipi_arg->cpu_mask);
> + }
> +
> + ret = hv_do_hypercall(HVCALL_SEND_IPI, ipi_arg, NULL);
> +
> +ipi_mask_done:
> + local_irq_restore(flags);
> + return ret;
> +}
> +
> +static int __send_ipi_one(int cpu, int vector)
> +{
> + struct cpumask mask = CPU_MASK_NONE;
> +
> + cpumask_set_cpu(cpu, &mask);
> + return __send_ipi_mask(&mask, vector);
> +}
> +
> +static void hv_send_ipi(int cpu, int vector)
> +{
> + if (__send_ipi_one(cpu, vector))
> + orig_apic.send_IPI(cpu, vector);
> +}
> +
> +static void hv_send_ipi_mask(const struct cpumask *mask, int vector)
> +{
> + if (__send_ipi_mask(mask, vector))
> + orig_apic.send_IPI_mask(mask, vector);
> +}
> +
> +static void hv_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
> +{
> + unsigned int this_cpu = smp_processor_id();
> + struct cpumask new_mask;
> + const struct cpumask *local_mask;
> +
> + cpumask_copy(&new_mask, mask);
> + cpumask_clear_cpu(this_cpu, &new_mask);
> + local_mask = &new_mask;
> + if (__send_ipi_mask(local_mask, vector))
> + orig_apic.send_IPI_mask_allbutself(mask, vector);
> +}
> +
> +static void hv_send_ipi_allbutself(int vector)
> +{
> + hv_send_ipi_mask_allbutself(cpu_online_mask, vector);
> +}
> +
> +static void hv_send_ipi_all(int vector)
> +{
> + if (__send_ipi_mask(cpu_online_mask, vector))
> + orig_apic.send_IPI_all(vector);
> +}
> +
> +static void hv_send_ipi_self(int vector)
> +{
> + if (__send_ipi_one(smp_processor_id(), vector))
> + orig_apic.send_IPI_self(vector);
> +}
> +
> void __init hv_apic_init(void)
> {
> + if (ms_hyperv.hints & HV_X64_CLUSTER_IPI_RECOMMENDED) {
> + if (hyperv_pcpu_input_arg == NULL)
> + goto msr_based_access;
> +
> + pr_info("Hyper-V: Using IPI hypercalls\n");
> + /*
> + * Set the IPI entry points.
> + */
> + orig_apic = *apic;
> +
> + apic->send_IPI = hv_send_ipi;
> + apic->send_IPI_mask = hv_send_ipi_mask;
> + apic->send_IPI_mask_allbutself = hv_send_ipi_mask_allbutself;
> + apic->send_IPI_allbutself = hv_send_ipi_allbutself;
> + apic->send_IPI_all = hv_send_ipi_all;
> + apic->send_IPI_self = hv_send_ipi_self;
> + }
> +
> +msr_based_access:
> if (ms_hyperv.hints & HV_X64_APIC_ACCESS_RECOMMENDED) {
> pr_info("Hyper-V: Using MSR ased APIC access\n");
> apic_set_eoi_write(hv_apic_eoi_write);
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 71e50fc2b7ef..a895662b6b4c 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -91,12 +91,19 @@ EXPORT_SYMBOL_GPL(hv_vp_index);
> struct hv_vp_assist_page **hv_vp_assist_page;
> EXPORT_SYMBOL_GPL(hv_vp_assist_page);
>
> +void __percpu **hyperv_pcpu_input_arg;
> +EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
> +
> u32 hv_max_vp_index;
>
> static int hv_cpu_init(unsigned int cpu)
> {
> u64 msr_vp_index;
> struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
> + void **input_arg;
> +
> + input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> + *input_arg = page_address(alloc_page(GFP_ATOMIC));
>
> hv_get_vp_index(msr_vp_index);
>
> @@ -217,6 +224,10 @@ static int hv_cpu_die(unsigned int cpu)
> {
> struct hv_reenlightenment_control re_ctrl;
> unsigned int new_cpu;
> + void **input_arg;
> +
> + input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> + free_page((unsigned long)*input_arg);
>
> if (hv_vp_assist_page && hv_vp_assist_page[cpu])
> wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
> @@ -260,6 +271,12 @@ void __init hyperv_init(void)
> if ((ms_hyperv.features & required_msrs) != required_msrs)
> return;
>
> + /* Allocate the per-CPU state for the hypercall input arg */
> + hyperv_pcpu_input_arg = alloc_percpu(void *);
> +
> + if (hyperv_pcpu_input_arg == NULL)
> + return;
> +
> /* Allocate percpu VP index */
> hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
> GFP_KERNEL);
> diff --git a/arch/x86/include/asm/hyperv-tlfs.h b/arch/x86/include/asm/hyperv-tlfs.h
> index 416cb0e0c496..646cf2ca2aaa 100644
> --- a/arch/x86/include/asm/hyperv-tlfs.h
> +++ b/arch/x86/include/asm/hyperv-tlfs.h
> @@ -164,6 +164,11 @@
> */
> #define HV_X64_DEPRECATING_AEOI_RECOMMENDED (1 << 9)
>
> +/*
> + * Recommend using cluster IPI hypercalls.
> + */
> +#define HV_X64_CLUSTER_IPI_RECOMMENDED (1 << 10)
> +
> /* Recommend using the newer ExProcessorMasks interface */
> #define HV_X64_EX_PROCESSOR_MASKS_RECOMMENDED (1 << 11)
>
> @@ -329,10 +334,14 @@ struct hv_tsc_emulation_status {
> #define HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_MASK \
> (~((1ull << HV_X64_MSR_HYPERCALL_PAGE_ADDRESS_SHIFT) - 1))
>
> +#define HV_IPI_LOW_VECTOR 0x10
> +#define HV_IPI_HIGH_VECTOR 0xff
> +
> /* Declare the various hypercall operations. */
> #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE 0x0002
> #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST 0x0003
> #define HVCALL_NOTIFY_LONG_SPIN_WAIT 0x0008
> +#define HVCALL_SEND_IPI 0x000b
> #define HVCALL_FLUSH_VIRTUAL_ADDRESS_SPACE_EX 0x0013
> #define HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX 0x0014
> #define HVCALL_POST_MESSAGE 0x005c
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index bcced50037c1..f6045f3611de 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -122,6 +122,7 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}
> #if IS_ENABLED(CONFIG_HYPERV)
> extern struct clocksource *hyperv_cs;
> extern void *hv_hypercall_pg;
> +extern void __percpu **hyperv_pcpu_input_arg;
>
> static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
> {
> --
> 2.15.1

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