Hi, Bibo,
On Sun, Apr 28, 2024 at 6:05 PM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
>
> PARAVIRT option and pv ipi is added on guest kernel side, function
> pv_ipi_init() is to add ipi sending and ipi receiving hooks. This function
> firstly checks whether system runs on VM mode. If kernel runs on VM mode,
> it will call function kvm_para_available() to detect current hypervirsor
> type. Now only KVM type detection is supported, the paravirt function can
> work only if current hypervisor type is KVM, since there is only KVM
> supported on LoongArch now.
>
> PV IPI uses virtual IPI sender and virtual IPI receiver function. With
> virutal IPI sender, ipi message is stored in DDR memory rather than
> emulated HW. IPI multicast is supported, and 128 vcpus can received IPIs
> at the same time like X86 KVM method. Hypercall method is used for IPI
> sending.
>
> With virtual IPI receiver, HW SW0 is used rather than real IPI HW. Since
> VCPU has separate HW SW0 like HW timer, there is no trap in IPI interrupt
> acknowledge. And IPI message is stored in DDR, no trap in get IPI message.
>
> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> ---
> arch/loongarch/Kconfig | 9 ++
> arch/loongarch/include/asm/hardirq.h | 1 +
> arch/loongarch/include/asm/paravirt.h | 27 ++++
> .../include/asm/paravirt_api_clock.h | 1 +
> arch/loongarch/kernel/Makefile | 1 +
> arch/loongarch/kernel/irq.c | 2 +-
> arch/loongarch/kernel/paravirt.c | 151 ++++++++++++++++++
> arch/loongarch/kernel/smp.c | 4 +-
> 8 files changed, 194 insertions(+), 2 deletions(-)
> create mode 100644 arch/loongarch/include/asm/paravirt.h
> create mode 100644 arch/loongarch/include/asm/paravirt_api_clock.h
> create mode 100644 arch/loongarch/kernel/paravirt.c
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 54ad04dacdee..0a1540a8853e 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -583,6 +583,15 @@ config CPU_HAS_PREFETCH
> bool
> default y
>
> +config PARAVIRT
> + bool "Enable paravirtualization code"
> + depends on AS_HAS_LVZ_EXTENSION
> + help
> + This changes the kernel so it can modify itself when it is run
> + under a hypervisor, potentially improving performance significantly
> + over full virtualization. However, when run without a hypervisor
> + the kernel is theoretically slower and slightly larger.
> +
> config ARCH_SUPPORTS_KEXEC
> def_bool y
>
> diff --git a/arch/loongarch/include/asm/hardirq.h b/arch/loongarch/include/asm/hardirq.h
> index 9f0038e19c7f..b26d596a73aa 100644
> --- a/arch/loongarch/include/asm/hardirq.h
> +++ b/arch/loongarch/include/asm/hardirq.h
> @@ -21,6 +21,7 @@ enum ipi_msg_type {
> typedef struct {
> unsigned int ipi_irqs[NR_IPI];
> unsigned int __softirq_pending;
> + atomic_t message ____cacheline_aligned_in_smp;
> } ____cacheline_aligned irq_cpustat_t;
>
> DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
> diff --git a/arch/loongarch/include/asm/paravirt.h b/arch/loongarch/include/asm/paravirt.h
> new file mode 100644
> index 000000000000..58f7b7b89f2c
> --- /dev/null
> +++ b/arch/loongarch/include/asm/paravirt.h
> @@ -0,0 +1,27 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef _ASM_LOONGARCH_PARAVIRT_H
> +#define _ASM_LOONGARCH_PARAVIRT_H
> +
> +#ifdef CONFIG_PARAVIRT
> +#include <linux/static_call_types.h>
> +struct static_key;
> +extern struct static_key paravirt_steal_enabled;
> +extern struct static_key paravirt_steal_rq_enabled;
> +
> +u64 dummy_steal_clock(int cpu);
> +DECLARE_STATIC_CALL(pv_steal_clock, dummy_steal_clock);
> +
> +static inline u64 paravirt_steal_clock(int cpu)
> +{
> + return static_call(pv_steal_clock)(cpu);
> +}
> +
> +int pv_ipi_init(void);
> +#else
> +static inline int pv_ipi_init(void)
> +{
> + return 0;
> +}
> +
> +#endif // CONFIG_PARAVIRT
> +#endif
> diff --git a/arch/loongarch/include/asm/paravirt_api_clock.h b/arch/loongarch/include/asm/paravirt_api_clock.h
> new file mode 100644
> index 000000000000..65ac7cee0dad
> --- /dev/null
> +++ b/arch/loongarch/include/asm/paravirt_api_clock.h
> @@ -0,0 +1 @@
> +#include <asm/paravirt.h>
> diff --git a/arch/loongarch/kernel/Makefile b/arch/loongarch/kernel/Makefile
> index 3a7620b66bc6..c9bfeda89e40 100644
> --- a/arch/loongarch/kernel/Makefile
> +++ b/arch/loongarch/kernel/Makefile
> @@ -51,6 +51,7 @@ obj-$(CONFIG_MODULES) += module.o module-sections.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
>
> obj-$(CONFIG_PROC_FS) += proc.o
> +obj-$(CONFIG_PARAVIRT) += paravirt.o
>
> obj-$(CONFIG_SMP) += smp.o
>
> diff --git a/arch/loongarch/kernel/irq.c b/arch/loongarch/kernel/irq.c
> index ce36897d1e5a..4863e6c1b739 100644
> --- a/arch/loongarch/kernel/irq.c
> +++ b/arch/loongarch/kernel/irq.c
> @@ -113,5 +113,5 @@ void __init init_IRQ(void)
> per_cpu(irq_stack, i), per_cpu(irq_stack, i) + IRQ_STACK_SIZE);
> }
>
> - set_csr_ecfg(ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 | ECFGF_IPI | ECFGF_PMC);
> + set_csr_ecfg(ECFGF_SIP0 | ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 | ECFGF_IPI | ECFGF_PMC);
> }
> diff --git a/arch/loongarch/kernel/paravirt.c b/arch/loongarch/kernel/paravirt.c
> new file mode 100644
> index 000000000000..9044ed62045c
> --- /dev/null
> +++ b/arch/loongarch/kernel/paravirt.c
> @@ -0,0 +1,151 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/export.h>
> +#include <linux/types.h>
> +#include <linux/interrupt.h>
> +#include <linux/jump_label.h>
> +#include <linux/kvm_para.h>
> +#include <asm/paravirt.h>
> +#include <linux/static_call.h>
> +
> +struct static_key paravirt_steal_enabled;
> +struct static_key paravirt_steal_rq_enabled;
> +
> +static u64 native_steal_clock(int cpu)
> +{
> + return 0;
> +}
> +
> +DEFINE_STATIC_CALL(pv_steal_clock, native_steal_clock);
> +
> +#ifdef CONFIG_SMP
> +static void pv_send_ipi_single(int cpu, unsigned int action)
> +{
> + unsigned int min, old;
> + irq_cpustat_t *info = &per_cpu(irq_stat, cpu);
> +
> + old = atomic_fetch_or(BIT(action), &info->message);
> + if (old)
> + return;
> +
> + min = cpu_logical_map(cpu);
> + kvm_hypercall3(KVM_HCALL_FUNC_PV_IPI, 1, 0, min);
> +}
> +
> +#define KVM_IPI_CLUSTER_SIZE (2 * BITS_PER_LONG)
> +static void pv_send_ipi_mask(const struct cpumask *mask, unsigned int action)
> +{
> + unsigned int cpu, i, min = 0, max = 0, old;
> + __uint128_t bitmap = 0;
> + irq_cpustat_t *info;
> +
> + if (cpumask_empty(mask))
> + return;
> +
> + action = BIT(action);
> + for_each_cpu(i, mask) {
> + info = &per_cpu(irq_stat, i);
> + old = atomic_fetch_or(action, &info->message);
> + if (old)
> + continue;
> +
> + cpu = cpu_logical_map(i);
> + if (!bitmap) {
> + min = max = cpu;
> + } else if (cpu > min && cpu < min + KVM_IPI_CLUSTER_SIZE) {
> + max = cpu > max ? cpu : max;
> + } else if (cpu < min && (max - cpu) < KVM_IPI_CLUSTER_SIZE) {
> + bitmap <<= min - cpu;
> + min = cpu;
> + } else {
> + /*
> + * Physical cpuid is sorted in ascending order ascend
> + * for the next mask calculation, send IPI here
> + * directly and skip the remainding cpus
> + */
> + kvm_hypercall3(KVM_HCALL_FUNC_PV_IPI,
> + (unsigned long)bitmap,
> + (unsigned long)(bitmap >> BITS_PER_LONG), min);
> + min = max = cpu;
> + bitmap = 0;
> + }
I have changed the logic and comments when I apply, you can double
check whether it is correct.
Huacai
> + __set_bit(cpu - min, (unsigned long *)&bitmap);
> + }
> +
> + if (bitmap)
> + kvm_hypercall3(KVM_HCALL_FUNC_PV_IPI, (unsigned long)bitmap,
> + (unsigned long)(bitmap >> BITS_PER_LONG), min);
> +}
> +
> +static irqreturn_t loongson_do_swi(int irq, void *dev)
> +{
> + irq_cpustat_t *info;
> + long action;
> +
> + /* Clear swi interrupt */
> + clear_csr_estat(1 << INT_SWI0);
> + info = this_cpu_ptr(&irq_stat);
> + action = atomic_xchg(&info->message, 0);
> + if (action & SMP_CALL_FUNCTION) {
> + generic_smp_call_function_interrupt();
> + info->ipi_irqs[IPI_CALL_FUNCTION]++;
> + }
> +
> + if (action & SMP_RESCHEDULE) {
> + scheduler_ipi();
> + info->ipi_irqs[IPI_RESCHEDULE]++;
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +static void pv_init_ipi(void)
> +{
> + int r, swi0;
> +
> + swi0 = get_percpu_irq(INT_SWI0);
> + if (swi0 < 0)
> + panic("SWI0 IRQ mapping failed\n");
> + irq_set_percpu_devid(swi0);
> + r = request_percpu_irq(swi0, loongson_do_swi, "SWI0", &irq_stat);
> + if (r < 0)
> + panic("SWI0 IRQ request failed\n");
> +}
> +#endif
> +
> +static bool kvm_para_available(void)
> +{
> + static int hypervisor_type;
> + int config;
> +
> + if (!hypervisor_type) {
> + config = read_cpucfg(CPUCFG_KVM_SIG);
> + if (!memcmp(&config, KVM_SIGNATURE, 4))
> + hypervisor_type = HYPERVISOR_KVM;
> + }
> +
> + return hypervisor_type == HYPERVISOR_KVM;
> +}
> +
> +int __init pv_ipi_init(void)
> +{
> + int feature;
> +
> + if (!cpu_has_hypervisor)
> + return 0;
> + if (!kvm_para_available())
> + return 0;
> +
> + /*
> + * check whether KVM hypervisor supports pv_ipi or not
> + */
> + feature = read_cpucfg(CPUCFG_KVM_FEATURE);
> +#ifdef CONFIG_SMP
> + if (feature & KVM_FEATURE_PV_IPI) {
> + smp_ops.init_ipi = pv_init_ipi;
> + smp_ops.send_ipi_single = pv_send_ipi_single;
> + smp_ops.send_ipi_mask = pv_send_ipi_mask;
> + }
> +#endif
> +
> + return 1;
> +}
> diff --git a/arch/loongarch/kernel/smp.c b/arch/loongarch/kernel/smp.c
> index 1fce775be4f6..9eff7aa4c552 100644
> --- a/arch/loongarch/kernel/smp.c
> +++ b/arch/loongarch/kernel/smp.c
> @@ -29,6 +29,7 @@
> #include <asm/loongson.h>
> #include <asm/mmu_context.h>
> #include <asm/numa.h>
> +#include <asm/paravirt.h>
> #include <asm/processor.h>
> #include <asm/setup.h>
> #include <asm/time.h>
> @@ -309,6 +310,7 @@ void __init loongson_smp_setup(void)
> cpu_data[0].core = cpu_logical_map(0) % loongson_sysconf.cores_per_package;
> cpu_data[0].package = cpu_logical_map(0) / loongson_sysconf.cores_per_package;
>
> + pv_ipi_init();
> iocsr_write32(0xffffffff, LOONGARCH_IOCSR_IPI_EN);
> pr_info("Detected %i available CPU(s)\n", loongson_sysconf.nr_cpus);
> }
> @@ -352,7 +354,7 @@ void loongson_boot_secondary(int cpu, struct task_struct *idle)
> void loongson_init_secondary(void)
> {
> unsigned int cpu = smp_processor_id();
> - unsigned int imask = ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 |
> + unsigned int imask = ECFGF_SIP0 | ECFGF_IP0 | ECFGF_IP1 | ECFGF_IP2 |
> ECFGF_IPI | ECFGF_PMC | ECFGF_TIMER;
>
> change_csr_ecfg(ECFG0_IM, imask);
> --
> 2.39.3
>
