Re: [PATCH v5 07/12] xen/arm: Add support for system suspend triggered by hardware domain

[Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>]

Hi Mykola,

Mykola Kvach <xakep.amatop@gmail.com> writes:

> From: Mirela Simonovic <mirela.simonovic@aggios.com>
>
> Trigger Xen suspend when the hardware domain initiates suspend via
> SHUTDOWN_suspend. Redirect system suspend to CPU#0 to ensure the
> suspend logic runs on the boot CPU, as required.
>
> Introduce full suspend/resume infrastructure gated by CONFIG_SYSTEM_SUSPEND,
> including logic to:
>  - disable and enable non-boot physical CPUs
>  - freeze and thaw domains
>  - suspend and resume the GIC, timer and console
>  - maintain system state before and after suspend
>
> Remove the restriction in the PSCI interface preventing suspend from the
> hardware domain.
>
> Select HAS_SYSTEM_SUSPEND for ARM_64.
>
> Signed-off-by: Mirela Simonovic <mirela.simonovic@aggios.com>
> Signed-off-by: Saeed Nowshadi <saeed.nowshadi@xilinx.com>
> Signed-off-by: Mykyta Poturai <mykyta_poturai@epam.com>
> Signed-off-by: Mykola Kvach <mykola_kvach@epam.com>
> ---
> Changes in v5:
> - select HAS_SYSTEM_SUSPEND in ARM_64 instead of ARM
> - check llc_coloring_enabled instead of LLC_COLORING during the selection
>   of HAS_SYSTEM_SUSPEND config
> - call host_system_suspend from guest PSCI system suspend instead of
>   arch_domain_shutdown, reducing the complexity of the new code
> - update some comments
>
> Changes introduced in V4:
>   - drop code for saving and restoring VCPU context (for more information
>     refer part 1 of patch series)
>   - remove IOMMU suspend and resume calls until they will be implemented
>   - move system suspend logic to arch_domain_shutdown, invoked from
>     domain_shutdown
>   - apply minor fixes such as renaming functions, updating comments, and
>     modifying the commit message to reflect these changes
>   - add console_end_sync to resume path after system suspend
>
> Changes introduced in V3:
>   - merge changes from other commits into this patch (previously stashed):
>     1) disable/enable non-boot physical CPUs and freeze/thaw domains during
>        suspend/resume
>     2) suspend/resume the timer, GIC, console, IOMMU, and hardware domain
> ---
>  xen/arch/arm/Kconfig               |   1 +
>  xen/arch/arm/Makefile              |   1 +
>  xen/arch/arm/include/asm/suspend.h |  22 +++++
>  xen/arch/arm/suspend.c             | 151 +++++++++++++++++++++++++++++
>  xen/arch/arm/vpsci.c               |  12 ++-
>  xen/common/domain.c                |   4 +
>  6 files changed, 190 insertions(+), 1 deletion(-)
>  create mode 100644 xen/arch/arm/include/asm/suspend.h
>  create mode 100644 xen/arch/arm/suspend.c
>
> diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig
> index a0c8160474..ccdbaa5bc3 100644
> --- a/xen/arch/arm/Kconfig
> +++ b/xen/arch/arm/Kconfig
> @@ -8,6 +8,7 @@ config ARM_64
>  	depends on !ARM_32
>  	select 64BIT
>  	select HAS_FAST_MULTIPLY
> +	select HAS_SYSTEM_SUSPEND if UNSUPPORTED
>  	select HAS_VPCI_GUEST_SUPPORT if PCI_PASSTHROUGH
>  
>  config ARM
> diff --git a/xen/arch/arm/Makefile b/xen/arch/arm/Makefile
> index f833cdf207..3f6247adee 100644
> --- a/xen/arch/arm/Makefile
> +++ b/xen/arch/arm/Makefile
> @@ -51,6 +51,7 @@ obj-y += setup.o
>  obj-y += shutdown.o
>  obj-y += smp.o
>  obj-y += smpboot.o
> +obj-$(CONFIG_SYSTEM_SUSPEND) += suspend.o
>  obj-$(CONFIG_SYSCTL) += sysctl.o
>  obj-y += time.o
>  obj-y += traps.o
> diff --git a/xen/arch/arm/include/asm/suspend.h b/xen/arch/arm/include/asm/suspend.h
> new file mode 100644
> index 0000000000..78d0e2383b
> --- /dev/null
> +++ b/xen/arch/arm/include/asm/suspend.h
> @@ -0,0 +1,22 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#ifndef __ASM_ARM_SUSPEND_H__
> +#define __ASM_ARM_SUSPEND_H__
> +
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +
> +int host_system_suspend(void);
> +
> +#endif /* CONFIG_SYSTEM_SUSPEND */
> +
> +#endif /* __ASM_ARM_SUSPEND_H__ */
> +
> + /*
> +  * Local variables:
> +  * mode: C
> +  * c-file-style: "BSD"
> +  * c-basic-offset: 4
> +  * tab-width: 4
> +  * indent-tabs-mode: nil
> +  * End:
> +  */
> diff --git a/xen/arch/arm/suspend.c b/xen/arch/arm/suspend.c
> new file mode 100644
> index 0000000000..abf4b928ce
> --- /dev/null
> +++ b/xen/arch/arm/suspend.c
> @@ -0,0 +1,151 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +
> +#include <xen/console.h>
> +#include <xen/cpu.h>
> +#include <xen/llc-coloring.h>
> +#include <xen/sched.h>
> +
> +/*
> + * TODO list:
> + *  - Test system suspend with LLC_COLORING enabled and verify functionality
> + *  - Implement IOMMU suspend/resume handlers and integrate them
> + *    into the suspend/resume path (IPMMU and SMMU)
> + *  - Enable "xl suspend" support on ARM architecture
> + *  - Properly disable Xen timer watchdog from relevant services
> + *  - Add suspend/resume CI test for ARM (QEMU if feasible)
> + *  - Investigate feasibility and need for implementing system suspend on ARM32
> + */
> +
> +/* Xen suspend. Note: data is not used (suspend is the suspend to RAM) */
> +static long system_suspend(void *data)
> +{
> +    int status;
> +    unsigned long flags;
> +
> +    BUG_ON(system_state != SYS_STATE_active);
> +
> +    system_state = SYS_STATE_suspend;
> +    freeze_domains();
> +    scheduler_disable();
> +
> +    /*
> +     * Non-boot CPUs have to be disabled on suspend and enabled on resume
> +     * (hotplug-based mechanism). Disabling non-boot CPUs will lead to PSCI
> +     * CPU_OFF to be called by each non-boot CPU. Depending on the underlying
> +     * platform capabilities, this may lead to the physical powering down of
> +     * CPUs. Tested on Xilinx Zynq Ultrascale+ MPSoC (including power down of
> +     * each non-boot CPU).

I don't think that the last part of the comment is relevant in upstream.

> +     */
> +    status = disable_nonboot_cpus();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_nonboot_cpus;
> +    }
> +
> +    time_suspend();
> +
> +    local_irq_save(flags);
> +    status = gic_suspend();
> +    if ( status )
> +    {
> +        system_state = SYS_STATE_resume;
> +        goto resume_irqs;
> +    }
> +
> +    printk("Xen suspending...\n");
> +
> +    console_start_sync();
> +    status = console_suspend();
> +    if ( status )
> +    {
> +        dprintk(XENLOG_ERR, "Failed to suspend the console, err=%d\n", status);
> +        system_state = SYS_STATE_resume;
> +        goto resume_console;
> +    }
> +
> +    /*
> +     * Enable identity mapping before entering suspend to simplify
> +     * the resume path
> +     */
> +    update_boot_mapping(true);
> +

This puzzles me. I expected actually PSCI suspend call here.

> +    system_state = SYS_STATE_resume;
> +    update_boot_mapping(false);
> +
> + resume_console:
> +    console_resume();
> +    console_end_sync();
> +
> +    gic_resume();
> +
> + resume_irqs:
> +    local_irq_restore(flags);
> +    time_resume();
> +
> + resume_nonboot_cpus:
> +    /*
> +     * The rcu_barrier() has to be added to ensure that the per cpu area is
> +     * freed before a non-boot CPU tries to initialize it (_free_percpu_area()
> +     * has to be called before the init_percpu_area()). This scenario occurs
> +     * when non-boot CPUs are hot-unplugged on suspend and hotplugged on resume.
> +     */
> +    rcu_barrier();
> +    enable_nonboot_cpus();
> +    scheduler_enable();
> +    thaw_domains();
> +
> +    system_state = SYS_STATE_active;
> +
> +    /* The resume of hardware domain should always follow Xen's resume. */
> +    domain_resume(hardware_domain);
> +
> +    printk("Resume (status %d)\n", status);
> +    return status;
> +}
> +
> +int host_system_suspend(void)
> +{
> +    int status;
> +
> +    /* TODO: drop check after verification that features can work together */
> +    if ( llc_coloring_enabled )
> +    {
> +        dprintk(XENLOG_ERR,
> +                "System suspend is not supported with LLC_COLORING enabled\n");
> +        return -ENOSYS;
> +    }
> +
> +    /*
> +     * system_suspend should be called when Dom0 finalizes the suspend
> +     * procedure from its boot core (VCPU#0). However, Dom0's VCPU#0 could
> +     * be mapped to any PCPU (this function could be executed by any PCPU).
> +     * The suspend procedure has to be finalized by the PCPU#0 (non-boot
> +     * PCPUs will be disabled during the suspend).
> +     */
> +    status = continue_hypercall_on_cpu(0, system_suspend, NULL);
> +
> +    /*
> +     * If an error happened, there is nothing that needs to be done here
> +     * because the system_suspend always returns in fully functional state
> +     * no matter what the outcome of suspend procedure is. If the system
> +     * suspended successfully the function will return 0 after the resume.
> +     * Otherwise, if an error is returned it means Xen did not suspended,
> +     * but it is still in the same state as if the system_suspend was never
> +     * called. We dump a debug message in case of an error for debugging/
> +     * logging purpose.
> +     */
> +    if ( status )
> +        dprintk(XENLOG_ERR, "Failed to suspend, errno=%d\n", status);
> +
> +    return status;
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/vpsci.c b/xen/arch/arm/vpsci.c
> index 67d369a8a2..757e719ea7 100644
> --- a/xen/arch/arm/vpsci.c
> +++ b/xen/arch/arm/vpsci.c
> @@ -4,6 +4,7 @@
>  #include <xen/types.h>
>  
>  #include <asm/current.h>
> +#include <asm/suspend.h>
>  #include <asm/vgic.h>
>  #include <asm/vpsci.h>
>  #include <asm/event.h>
> @@ -214,9 +215,10 @@ static int32_t do_psci_1_0_system_suspend(register_t epoint, register_t cid)
>      struct vcpu *v;
>      struct domain *d = current->domain;
>  
> -    /* SYSTEM_SUSPEND is not supported for the hardware domain yet */
> +#ifndef CONFIG_SYSTEM_SUSPEND
>      if ( is_hardware_domain(d) )
>          return PSCI_NOT_SUPPORTED;
> +#endif
>  
>      /* Ensure that all CPUs other than the calling one are offline */
>      domain_lock(d);
> @@ -234,6 +236,14 @@ static int32_t do_psci_1_0_system_suspend(register_t epoint, register_t cid)
>      if ( rc )
>          return PSCI_DENIED;
>  
> +#ifdef CONFIG_SYSTEM_SUSPEND
> +    if ( is_hardware_domain(d) && host_system_suspend() )
> +    {
> +        domain_resume_nopause(d);
> +        return PSCI_DENIED;
> +    }
> +#endif
> +
>      rc = do_setup_vcpu_ctx(current, epoint, cid);
>      if ( rc != PSCI_SUCCESS )
>      {
> diff --git a/xen/common/domain.c b/xen/common/domain.c
> index c3609b0cb0..414a691242 100644
> --- a/xen/common/domain.c
> +++ b/xen/common/domain.c
> @@ -1311,7 +1311,11 @@ int domain_shutdown(struct domain *d, u8 reason)
>          d->shutdown_code = reason;
>      reason = d->shutdown_code;
>  
> +#if defined(CONFIG_SYSTEM_SUSPEND) && defined(CONFIG_ARM)
> +    if ( reason != SHUTDOWN_suspend && is_hardware_domain(d) )
> +#else
>      if ( is_hardware_domain(d) )
> +#endif
>          hwdom_shutdown(reason);
>  
>      if ( d->is_shutting_down )

-- 
WBR, Volodymyr