On Mon, Feb 19, 2024 at 12:18 PM maobibo <maobibo@xxxxxxxxxxx> wrote:
>
>
>
> On 2024/2/19 上午10:45, Huacai Chen wrote:
> > Hi, Bibo,
> >
> > On Thu, Feb 1, 2024 at 11:20 AM Bibo Mao <maobibo@xxxxxxxxxxx> wrote:
> >>
> >> On LoongArch system, ipi hw uses iocsr registers, there is one iocsr
> >> register access on ipi sending, and two iocsr access on ipi receiving
> >> which is ipi interrupt handler. On VM mode all iocsr registers
> >> accessing will cause VM to trap into hypervisor. So with ipi hw
> >> notification once there will be three times of trap.
> >>
> >> This patch adds pv ipi support for VM, hypercall instruction is used
> >> to ipi sender, and hypervisor will inject SWI on the VM. During SWI
> >> interrupt handler, only estat CSR register is written to clear irq.
> >> Estat CSR register access will not trap into hypervisor. So with pv ipi
> >> supported, pv ipi sender will trap into hypervsor one time, pv ipi
> >> revicer will not trap, there is only one time of trap.
> >>
> >> Also this patch adds ipi multicast support, the method is similar with
> >> x86. With ipi multicast support, ipi notification can be sent to at most
> >> 128 vcpus at one time. It reduces trap times into hypervisor greatly.
> >>
> >> Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
> >> ---
> >> arch/loongarch/include/asm/hardirq.h | 1 +
> >> arch/loongarch/include/asm/kvm_host.h | 1 +
> >> arch/loongarch/include/asm/kvm_para.h | 124 +++++++++++++++++++++++++
> >> arch/loongarch/include/asm/loongarch.h | 1 +
> >> arch/loongarch/kernel/irq.c | 2 +-
> >> arch/loongarch/kernel/paravirt.c | 113 ++++++++++++++++++++++
> >> arch/loongarch/kernel/smp.c | 2 +-
> >> arch/loongarch/kvm/exit.c | 73 ++++++++++++++-
> >> arch/loongarch/kvm/vcpu.c | 1 +
> >> 9 files changed, 314 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/arch/loongarch/include/asm/hardirq.h b/arch/loongarch/include/asm/hardirq.h
> >> index 9f0038e19c7f..8a611843c1f0 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 messages ____cacheline_aligned_in_smp;
> > Do we really need atomic_t? A plain "unsigned int" can reduce cost
> > significantly.
> For IPI, there are multiple senders and one receiver, the sender uses
> atomic_fetch_or(action, &info->messages) and the receiver uses
> atomic_xchg(&info->messages, 0) to clear message.
>
> There needs sync mechanism between senders and receiver, atomic is the
> most simple method.
At least from receiver side, the native IPI doesn't need atomic for
read and clear:
static u32 ipi_read_clear(int cpu)
{
u32 action;
/* Load the ipi register to figure out what we're supposed to do */
action = iocsr_read32(LOONGARCH_IOCSR_IPI_STATUS);
/* Clear the ipi register to clear the interrupt */
iocsr_write32(action, LOONGARCH_IOCSR_IPI_CLEAR);
wbflush();
return action;
}
> >
> >> } ____cacheline_aligned irq_cpustat_t;
> >>
> >> DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat);
> >> diff --git a/arch/loongarch/include/asm/kvm_host.h b/arch/loongarch/include/asm/kvm_host.h
> >> index 57399d7cf8b7..1bf927e2bfac 100644
> >> --- a/arch/loongarch/include/asm/kvm_host.h
> >> +++ b/arch/loongarch/include/asm/kvm_host.h
> >> @@ -43,6 +43,7 @@ struct kvm_vcpu_stat {
> >> u64 idle_exits;
> >> u64 cpucfg_exits;
> >> u64 signal_exits;
> >> + u64 hvcl_exits;
> > hypercall_exits is better.
> yeap, hypercall_exits is better, will fix in next version.
> >
> >> };
> >>
> >> #define KVM_MEM_HUGEPAGE_CAPABLE (1UL << 0)
> >> diff --git a/arch/loongarch/include/asm/kvm_para.h b/arch/loongarch/include/asm/kvm_para.h
> >> index 41200e922a82..a25a84e372b9 100644
> >> --- a/arch/loongarch/include/asm/kvm_para.h
> >> +++ b/arch/loongarch/include/asm/kvm_para.h
> >> @@ -9,6 +9,10 @@
> >> #define HYPERVISOR_VENDOR_SHIFT 8
> >> #define HYPERCALL_CODE(vendor, code) ((vendor << HYPERVISOR_VENDOR_SHIFT) + code)
> >>
> >> +#define KVM_HC_CODE_SERVICE 0
> >> +#define KVM_HC_SERVICE HYPERCALL_CODE(HYPERVISOR_KVM, KVM_HC_CODE_SERVICE)
> >> +#define KVM_HC_FUNC_IPI 1
> > Change HC to HCALL is better.
> will modify in next version.
> >
> >> +
> >> /*
> >> * LoongArch hypcall return code
> >> */
> >> @@ -16,6 +20,126 @@
> >> #define KVM_HC_INVALID_CODE -1UL
> >> #define KVM_HC_INVALID_PARAMETER -2UL
> >>
> >> +/*
> >> + * Hypercalls interface for KVM hypervisor
> >> + *
> >> + * a0: function identifier
> >> + * a1-a6: args
> >> + * Return value will be placed in v0.
> >> + * Up to 6 arguments are passed in a1, a2, a3, a4, a5, a6.
> >> + */
> >> +static __always_inline long kvm_hypercall(u64 fid)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r" (fun)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static __always_inline long kvm_hypercall1(u64 fid, unsigned long arg0)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> + register unsigned long a1 asm("a1") = arg0;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r" (fun), "r" (a1)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static __always_inline long kvm_hypercall2(u64 fid,
> >> + unsigned long arg0, unsigned long arg1)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> + register unsigned long a1 asm("a1") = arg0;
> >> + register unsigned long a2 asm("a2") = arg1;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r" (fun), "r" (a1), "r" (a2)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static __always_inline long kvm_hypercall3(u64 fid,
> >> + unsigned long arg0, unsigned long arg1, unsigned long arg2)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> + register unsigned long a1 asm("a1") = arg0;
> >> + register unsigned long a2 asm("a2") = arg1;
> >> + register unsigned long a3 asm("a3") = arg2;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r" (fun), "r" (a1), "r" (a2), "r" (a3)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static __always_inline long kvm_hypercall4(u64 fid,
> >> + unsigned long arg0, unsigned long arg1, unsigned long arg2,
> >> + unsigned long arg3)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> + register unsigned long a1 asm("a1") = arg0;
> >> + register unsigned long a2 asm("a2") = arg1;
> >> + register unsigned long a3 asm("a3") = arg2;
> >> + register unsigned long a4 asm("a4") = arg3;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r"(fun), "r" (a1), "r" (a2), "r" (a3), "r" (a4)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +static __always_inline long kvm_hypercall5(u64 fid,
> >> + unsigned long arg0, unsigned long arg1, unsigned long arg2,
> >> + unsigned long arg3, unsigned long arg4)
> >> +{
> >> + register long ret asm("v0");
> >> + register unsigned long fun asm("a0") = fid;
> >> + register unsigned long a1 asm("a1") = arg0;
> >> + register unsigned long a2 asm("a2") = arg1;
> >> + register unsigned long a3 asm("a3") = arg2;
> >> + register unsigned long a4 asm("a4") = arg3;
> >> + register unsigned long a5 asm("a5") = arg4;
> >> +
> >> + __asm__ __volatile__(
> >> + "hvcl "__stringify(KVM_HC_SERVICE)
> >> + : "=r" (ret)
> >> + : "r"(fun), "r" (a1), "r" (a2), "r" (a3), "r" (a4), "r" (a5)
> >> + : "memory"
> >> + );
> >> +
> >> + return ret;
> >> +}
> >> +
> >> +
> >> static inline unsigned int kvm_arch_para_features(void)
> >> {
> >> return 0;
> >> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> >> index a1d22e8b6f94..0ad36704cb4b 100644
> >> --- a/arch/loongarch/include/asm/loongarch.h
> >> +++ b/arch/loongarch/include/asm/loongarch.h
> >> @@ -167,6 +167,7 @@
> >> #define CPUCFG_KVM_SIG CPUCFG_KVM_BASE
> >> #define KVM_SIGNATURE "KVM\0"
> >> #define CPUCFG_KVM_FEATURE (CPUCFG_KVM_BASE + 4)
> >> +#define KVM_FEATURE_PV_IPI BIT(1)
> >>
> >> #ifndef __ASSEMBLY__
> >>
> >> 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
> >> index 21d01d05791a..7a8319df401c 100644
> >> --- a/arch/loongarch/kernel/paravirt.c
> >> +++ b/arch/loongarch/kernel/paravirt.c
> >> @@ -1,6 +1,7 @@
> >> // 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>
> >> @@ -16,6 +17,104 @@ static u64 native_steal_clock(int cpu)
> >>
> >> 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;
> >> + unsigned long bitmap = 0;
> >> + irq_cpustat_t *info = &per_cpu(irq_stat, cpu);
> >> +
> >> + action = BIT(action);
> >> + old = atomic_fetch_or(action, &info->messages);
> >> + if (old == 0) {
> >> + min = cpu_logical_map(cpu);
> >> + bitmap = 1;
> >> + kvm_hypercall3(KVM_HC_FUNC_IPI, bitmap, 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->messages);
> >> + 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_HC_FUNC_IPI, (unsigned long)bitmap,
> >> + (unsigned long)(bitmap >> BITS_PER_LONG), min);
> >> + min = max = cpu;
> >> + bitmap = 0;
> >> + }
> >> + __set_bit(cpu - min, (unsigned long *)&bitmap);
> >> + }
> >> +
> >> + if (bitmap)
> >> + kvm_hypercall3(KVM_HC_FUNC_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_csr_estat(1 << INT_SWI0);
> >> +
> >> + info = this_cpu_ptr(&irq_stat);
> >> + do {
> >> + action = atomic_xchg(&info->messages, 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]++;
> >> + }
> >> + } while (action);
> >> +
> >> + 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;
> >> @@ -32,10 +131,24 @@ static bool kvm_para_available(void)
> >>
> >> int __init pv_guest_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
> >> + */
> >> +#ifdef CONFIG_SMP
> >> + feature = read_cpucfg(CPUCFG_KVM_FEATURE);
> > This line can be moved out of CONFIG_SMP, especially features will
> > increase in future.
> Good suggestion, will modify in next version.
>
> Regards
> Bibo Mao
> >
> > Huacai
> >
> >> + 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 3d3ec07d1ec4..d50443879353 100644
> >> --- a/arch/loongarch/kernel/smp.c
> >> +++ b/arch/loongarch/kernel/smp.c
> >> @@ -285,7 +285,7 @@ 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);
> >> diff --git a/arch/loongarch/kvm/exit.c b/arch/loongarch/kvm/exit.c
> >> index f4e4df05f578..189b70bad825 100644
> >> --- a/arch/loongarch/kvm/exit.c
> >> +++ b/arch/loongarch/kvm/exit.c
> >> @@ -227,6 +227,9 @@ static int kvm_emu_cpucfg(struct kvm_vcpu *vcpu, larch_inst inst)
> >> case CPUCFG_KVM_SIG:
> >> vcpu->arch.gprs[rd] = *(unsigned int *)KVM_SIGNATURE;
> >> break;
> >> + case CPUCFG_KVM_FEATURE:
> >> + vcpu->arch.gprs[rd] = KVM_FEATURE_PV_IPI;
> >> + break;
> >> default:
> >> vcpu->arch.gprs[rd] = 0;
> >> break;
> >> @@ -699,12 +702,78 @@ static int kvm_handle_lasx_disabled(struct kvm_vcpu *vcpu)
> >> return RESUME_GUEST;
> >> }
> >>
> >> +static int kvm_pv_send_ipi(struct kvm_vcpu *vcpu)
> >> +{
> >> + unsigned long ipi_bitmap;
> >> + unsigned int min, cpu, i;
> >> + struct kvm_vcpu *dest;
> >> +
> >> + min = vcpu->arch.gprs[LOONGARCH_GPR_A3];
> >> + for (i = 0; i < 2; i++) {
> >> + ipi_bitmap = vcpu->arch.gprs[LOONGARCH_GPR_A1 + i];
> >> + if (!ipi_bitmap)
> >> + continue;
> >> +
> >> + cpu = find_first_bit((void *)&ipi_bitmap, BITS_PER_LONG);
> >> + while (cpu < BITS_PER_LONG) {
> >> + dest = kvm_get_vcpu_by_cpuid(vcpu->kvm, cpu + min);
> >> + cpu = find_next_bit((void *)&ipi_bitmap, BITS_PER_LONG,
> >> + cpu + 1);
> >> + if (!dest)
> >> + continue;
> >> +
> >> + /*
> >> + * Send SWI0 to dest vcpu to emulate IPI interrupt
> >> + */
> >> + kvm_queue_irq(dest, INT_SWI0);
> >> + kvm_vcpu_kick(dest);
> >> + }
> >> + }
> >> +
> >> + return 0;
> >> +}
> >> +
> >> +/*
> >> + * hypcall emulation always return to guest, Caller should check retval.
> >> + */
> >> +static void kvm_handle_pv_hcall(struct kvm_vcpu *vcpu)
> > Rename to kvm_handle_hypecall_service() is better.
> >
> >
> > Huacai
> >> +{
> >> + unsigned long func = vcpu->arch.gprs[LOONGARCH_GPR_A0];
> >> + long ret;
> >> +
> >> + switch (func) {
> >> + case KVM_HC_FUNC_IPI:
> >> + kvm_pv_send_ipi(vcpu);
> >> + ret = KVM_HC_STATUS_SUCCESS;
> >> + break;
> >> + default:
> >> + ret = KVM_HC_INVALID_CODE;
> >> + break;
> >> + };
> >> +
> >> + vcpu->arch.gprs[LOONGARCH_GPR_A0] = ret;
> >> +}
> >> +
> >> static int kvm_handle_hypcall(struct kvm_vcpu *vcpu)
> >> {
> >> + larch_inst inst;
> >> + unsigned int code;
> >> +
> >> + inst.word = vcpu->arch.badi;
> >> + code = inst.reg0i15_format.immediate;
> >> update_pc(&vcpu->arch);
> >>
> >> - /* Treat it as noop intruction, only set return value */
> >> - vcpu->arch.gprs[LOONGARCH_GPR_A0] = KVM_HC_INVALID_CODE;
> >> + switch (code) {
> >> + case KVM_HC_SERVICE:
> >> + vcpu->stat.hvcl_exits++;
> >> + kvm_handle_pv_hcall(vcpu);
> >> + break;
> >> + default:
> >> + /* Treat it as noop intruction, only set return value */
> >> + vcpu->arch.gprs[LOONGARCH_GPR_A0] = KVM_HC_INVALID_CODE;
> >> + break;
> >> + }
> >> +
> >> return RESUME_GUEST;
> >> }
> >>
> >> diff --git a/arch/loongarch/kvm/vcpu.c b/arch/loongarch/kvm/vcpu.c
> >> index 97ca9c7160e6..80e05ba9b48d 100644
> >> --- a/arch/loongarch/kvm/vcpu.c
> >> +++ b/arch/loongarch/kvm/vcpu.c
> >> @@ -19,6 +19,7 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
> >> STATS_DESC_COUNTER(VCPU, idle_exits),
> >> STATS_DESC_COUNTER(VCPU, cpucfg_exits),
> >> STATS_DESC_COUNTER(VCPU, signal_exits),
> >> + STATS_DESC_COUNTER(VCPU, hvcl_exits)
> >> };
> >>
> >> const struct kvm_stats_header kvm_vcpu_stats_header = {
> >> --
> >> 2.39.3
> >>
>
