Re: [PATCH RFC V2 07/37] arm/virt, gicv3: Changes to pre-size GIC with possible vcpus @machine init

[Gavin Shan]

Hi Salil,

On 9/26/23 20:04, Salil Mehta wrote:
> GIC needs to be pre-sized with possible vcpus at the initialization time. This
> is necessary because Memory regions and resources associated with GICC/GICR
> etc cannot be changed (add/del/modified) after VM has inited. Also, GIC_TYPER
> needs to be initialized with mp_affinity and cpu interface number association.
> This cannot be changed after GIC has initialized.
>
> Once all the cpu interfaces of the GIC has been inited it needs to be ensured
                                                  ^^^^^^
                                                  initialized,
> that any updates to the GICC during reset only takes place for the present
                                                                 ^^^^^^^^^^^
                                                                 the enabled
> vcpus and not the disabled ones. Therefore, proper checks are required at
> various places.
>
> Co-developed-by: Salil Mehta <salil.mehta@huawei.com>
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> Co-developed-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> [changed the comment in arm_gicv3_icc_reset]
> Signed-off-by: Salil Mehta <salil.mehta@huawei.com>
> ---
>   hw/arm/virt.c              | 15 ++++++++-------
>   hw/intc/arm_gicv3_common.c |  7 +++++--
>   hw/intc/arm_gicv3_cpuif.c  |  8 ++++++++
>   hw/intc/arm_gicv3_kvm.c    | 34 +++++++++++++++++++++++++++++++---
>   include/hw/arm/virt.h      |  2 +-
>   5 files changed, 53 insertions(+), 13 deletions(-)

I guess the subject can be improved to something like below because it's the 
preparatory
work to support vCPU hotplug (notifier) in the subsequent patches. In this 
patch, most
of the code changes is related to vCPU state, ms->smp_pros.max_cpus and the CPU 
interface
instances associated to GICv3 controller.

arm/virt,gicv3: Prepare for vCPU hotplug by checking GICv3CPUState states

We already had wrappers to check vCPU's states. I'm wandering if we need 
another set
of wrappers for GICv3 for several facts: (a) In this patch, we're actually 
concerned
by GICv3CPUState's states, disabled or enabled. vCPU states have been 
classified to
possible, present, and enabled. Their states aren't matching strictly. (b) With 
GICv3
own wrappers, the code can be detached from vCPU in high level. Please evaluate 
it's
worthy to have GICv3 own wrappers and we can have the folowing wrappers if want.

/*
 * The association between GICv3CPUState and ARMCPU happens in
 * arm_gicv3_common_realize(). After that, gicv3_cpuif_is_ready()
 * can be used.
 */
static inline bool gicv3_cpuif_is_ready(GICv3State *s, int index)
{
    if (!s->cpu || index >= s->num_cpu || !s->cpu[index].cpu) {
        return false;
    }

    return true;
}


> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 6ba131b799..a208b4e517 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -718,6 +718,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion 
> *mem)
>       const char *gictype;
>       int i;
>       unsigned int smp_cpus = ms->smp.cpus;
> +    unsigned int max_cpus = ms->smp.max_cpus;
>       uint32_t nb_redist_regions = 0;
>       int revision;
>   
> @@ -742,7 +743,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion *mem)
>       }
>       vms->gic = qdev_new(gictype);
>       qdev_prop_set_uint32(vms->gic, "revision", revision);
> -    qdev_prop_set_uint32(vms->gic, "num-cpu", smp_cpus);
> +    qdev_prop_set_uint32(vms->gic, "num-cpu", max_cpus);
>       /* Note that the num-irq property counts both internal and external
>        * interrupts; there are always 32 of the former (mandated by GIC spec).
>        */
> @@ -753,7 +754,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion 
> *mem)
>   
>       if (vms->gic_version != VIRT_GIC_VERSION_2) {
>           uint32_t redist0_capacity = virt_redist_capacity(vms, 
> VIRT_GIC_REDIST);
> -        uint32_t redist0_count = MIN(smp_cpus, redist0_capacity);
> +        uint32_t redist0_count = MIN(max_cpus, redist0_capacity);
>   
>           nb_redist_regions = virt_gicv3_redist_region_count(vms);
>   
> @@ -774,7 +775,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion *mem)
>                   virt_redist_capacity(vms, VIRT_HIGH_GIC_REDIST2);
>   
>               qdev_prop_set_uint32(vms->gic, "redist-region-count[1]",
> -                MIN(smp_cpus - redist0_count, redist1_capacity));
> +                MIN(max_cpus - redist0_count, redist1_capacity));
>           }
>       } else {
>           if (!kvm_irqchip_in_kernel()) {
> @@ -831,7 +832,7 @@ static void create_gic(VirtMachineState *vms, MemoryRegion 
> *mem)
>           } else if (vms->virt) {
>               qemu_irq irq = qdev_get_gpio_in(vms->gic,
>                                               ppibase + ARCH_GIC_MAINT_IRQ);
> -            sysbus_connect_irq(gicbusdev, i + 4 * smp_cpus, irq);
> +            sysbus_connect_irq(gicbusdev, i + 4 * max_cpus, irq);
>           }
>   
>           qdev_connect_gpio_out_named(cpudev, "pmu-interrupt", 0,
> @@ -839,11 +840,11 @@ static void create_gic(VirtMachineState *vms, 
> MemoryRegion *mem)
>                                                        + VIRTUAL_PMU_IRQ));
>   
>           sysbus_connect_irq(gicbusdev, i, qdev_get_gpio_in(cpudev, ARM_CPU_IRQ));
> -        sysbus_connect_irq(gicbusdev, i + smp_cpus,
> +        sysbus_connect_irq(gicbusdev, i + max_cpus,
>                              qdev_get_gpio_in(cpudev, ARM_CPU_FIQ));
> -        sysbus_connect_irq(gicbusdev, i + 2 * smp_cpus,
> +        sysbus_connect_irq(gicbusdev, i + 2 * max_cpus,
>                              qdev_get_gpio_in(cpudev, ARM_CPU_VIRQ));
> -        sysbus_connect_irq(gicbusdev, i + 3 * smp_cpus,
> +        sysbus_connect_irq(gicbusdev, i + 3 * max_cpus,
>                              qdev_get_gpio_in(cpudev, ARM_CPU_VFIQ));
>       }
>   
> diff --git a/hw/intc/arm_gicv3_common.c b/hw/intc/arm_gicv3_common.c
> index 2ebf880ead..ebd99af610 100644
> --- a/hw/intc/arm_gicv3_common.c
> +++ b/hw/intc/arm_gicv3_common.c
> @@ -392,10 +392,13 @@ static void arm_gicv3_common_realize(DeviceState *dev, 
> Error **errp)
>       s->cpu = g_new0(GICv3CPUState, s->num_cpu);
>   
>       for (i = 0; i < s->num_cpu; i++) {
> -        CPUState *cpu = qemu_get_cpu(i);
> +        CPUState *cpu = qemu_get_possible_cpu(i);
>           uint64_t cpu_affid;
>   
> -        s->cpu[i].cpu = cpu;
> +        if (qemu_enabled_cpu(cpu)) {
> +            s->cpu[i].cpu = cpu;
> +        }
> +
>           s->cpu[i].gic = s;
>           /* Store GICv3CPUState in CPUARMState gicv3state pointer */
>           gicv3_set_gicv3state(cpu, &s->cpu[i]);

I don't think gicv3_set_gicv3state() isn't needed for !qemu_enabled_cpu(cpu)
since those disabled vCPUs will be released in hw/arm/virt.c pretty soon.

> diff --git a/hw/intc/arm_gicv3_cpuif.c b/hw/intc/arm_gicv3_cpuif.c
> index d07b13eb27..7b7a0fdb9c 100644
> --- a/hw/intc/arm_gicv3_cpuif.c
> +++ b/hw/intc/arm_gicv3_cpuif.c
> @@ -934,6 +934,10 @@ void gicv3_cpuif_update(GICv3CPUState *cs)
>       ARMCPU *cpu = ARM_CPU(cs->cpu);
>       CPUARMState *env = &cpu->env;
>   
> +    if (!qemu_enabled_cpu(cs->cpu)) {
> +        return;
> +    }
> +

The question is how it's possible. It seems a bug to update GICv3CPUState
who isn't ready or disabled.

>       g_assert(qemu_mutex_iothread_locked());
>   
>       trace_gicv3_cpuif_update(gicv3_redist_affid(cs), cs->hppi.irq,
> @@ -1826,6 +1830,10 @@ static void icc_generate_sgi(CPUARMState *env, 
> GICv3CPUState *cs,
>       for (i = 0; i < s->num_cpu; i++) {
>           GICv3CPUState *ocs = &s->cpu[i];
>   
> +        if (!qemu_enabled_cpu(ocs->cpu)) {
> +            continue;
> +        }
> +
>           if (irm) {
>               /* IRM == 1 : route to all CPUs except self */
>               if (cs == ocs) {
> diff --git a/hw/intc/arm_gicv3_kvm.c b/hw/intc/arm_gicv3_kvm.c
> index 72ad916d3d..b6f50caf84 100644
> --- a/hw/intc/arm_gicv3_kvm.c
> +++ b/hw/intc/arm_gicv3_kvm.c
> @@ -24,6 +24,7 @@
>   #include "hw/intc/arm_gicv3_common.h"
>   #include "qemu/error-report.h"
>   #include "qemu/module.h"
> +#include "sysemu/cpus.h"
>   #include "sysemu/kvm.h"
>   #include "sysemu/runstate.h"
>   #include "kvm_arm.h"
> @@ -458,6 +459,18 @@ static void kvm_arm_gicv3_put(GICv3State *s)
>           GICv3CPUState *c = &s->cpu[ncpu];
>           int num_pri_bits;
>   
> +        /*
> +         * To support hotplug of vcpus we need to make sure all gic cpuif/GICC
> +         * are initialized at machvirt init time. Once the init is done we
> +         * release the ARMCPU object for disabled vcpus but this leg could hit
> +         * during reset of GICC later as well i.e. after init has happened and
> +         * all of the cases we want to make sure we dont acess the GICC for
> +         * the disabled VCPUs.
> +         */
> +        if (!qemu_enabled_cpu(c->cpu)) {
> +            continue;
> +        }
> +
>           kvm_gicc_access(s, ICC_SRE_EL1, ncpu, &c->icc_sre_el1, true);
>           kvm_gicc_access(s, ICC_CTLR_EL1, ncpu,
>                           &c->icc_ctlr_el1[GICV3_NS], true);
> @@ -616,6 +629,11 @@ static void kvm_arm_gicv3_get(GICv3State *s)
>           GICv3CPUState *c = &s->cpu[ncpu];
>           int num_pri_bits;
>   
> +        /* don't access GICC for the disabled vCPUs. */
> +        if (!qemu_enabled_cpu(c->cpu)) {
> +            continue;
> +        }
> +
>           kvm_gicc_access(s, ICC_SRE_EL1, ncpu, &c->icc_sre_el1, false);
>           kvm_gicc_access(s, ICC_CTLR_EL1, ncpu,
>                           &c->icc_ctlr_el1[GICV3_NS], false);
> @@ -695,10 +713,19 @@ static void arm_gicv3_icc_reset(CPUARMState *env, const 
> ARMCPRegInfo *ri)
>           return;
>       }
>   
> +    /*
> +     * This shall be called even when vcpu is being hotplugged or onlined and
> +     * other vcpus might be running. Host kernel KVM code to handle device
> +     * access of IOCTLs KVM_{GET|SET}_DEVICE_ATTR might fail due to inability 
> to
> +     * grab vcpu locks for all the vcpus. Hence, we need to pause all vcpus to
> +     * facilitate locking within host.
> +     */
> +    pause_all_vcpus();
>       /* Initialize to actual HW supported configuration */
>       kvm_device_access(s->dev_fd, KVM_DEV_ARM_VGIC_GRP_CPU_SYSREGS,
>                         KVM_VGIC_ATTR(ICC_CTLR_EL1, c->gicr_typer),
>                         &c->icc_ctlr_el1[GICV3_NS], false, &error_abort);
> +    resume_all_vcpus();

Please swap the positions for paused_all_vcpu() and the next comment, and
then combine the comments.

>   
>       c->icc_ctlr_el1[GICV3_S] = c->icc_ctlr_el1[GICV3_NS];
>   }
> @@ -808,9 +835,10 @@ static void kvm_arm_gicv3_realize(DeviceState *dev, Error 
> **errp)
>       gicv3_init_irqs_and_mmio(s, kvm_arm_gicv3_set_irq, NULL);
>   
>       for (i = 0; i < s->num_cpu; i++) {
> -        ARMCPU *cpu = ARM_CPU(qemu_get_cpu(i));
> -
> -        define_arm_cp_regs(cpu, gicv3_cpuif_reginfo);
> +        CPUState *cs = qemu_get_cpu(i);
> +        if (qemu_enabled_cpu(cs)) {
> +            define_arm_cp_regs(ARM_CPU(cs), gicv3_cpuif_reginfo);
> +        }
>       }
>   
>       /* Try to create the device via the device control API */
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index 13163adb07..098c7917a4 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -217,7 +217,7 @@ static inline int 
> virt_gicv3_redist_region_count(VirtMachineState *vms)
>   
>       assert(vms->gic_version != VIRT_GIC_VERSION_2);
>   
> -    return (MACHINE(vms)->smp.cpus > redist0_capacity &&
> +    return (MACHINE(vms)->smp.max_cpus > redist0_capacity &&
>               vms->highmem_redists) ? 2 : 1;
>   }
>   

Thanks,
Gavin