Re: [Qemu-devel] [PATCH 21/23] hw/arm/virt: Support using SMC for PSCI

[Edgar E. Iglesias]

On Tue, Dec 13, 2016 at 10:36:22AM +0000, Peter Maydell wrote:
> If we are giving the guest a CPU with EL2, it is likely to
> want to use the HVC instruction itself, for instance for
> providing PSCI to inner guest VMs. This makes using HVC
> as the PSCI conduit for the outer QEMU a bad idea. We will
> want to use SMC instead is this case: this makes sense
> because QEMU's PSCI implementation is effectively an
> emulation of functionality provided by EL3 firmware.
> 
> Add code to support selecting the PSCI conduit to use,
> rather than hardcoding use of HVC.
> 
> Signed-off-by: Peter Maydell <address@hidden>

Reviewed-by: Edgar E. Iglesias <address@hidden>


> ---
>  hw/arm/virt.c | 29 ++++++++++++++++++++++-------
>  1 file changed, 22 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 7adb58b..cce8d2e 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -88,7 +88,7 @@ typedef struct {
>      uint32_t clock_phandle;
>      uint32_t gic_phandle;
>      uint32_t msi_phandle;
> -    bool using_psci;
> +    int psci_conduit;
>  } VirtMachineState;
>  
>  #define TYPE_VIRT_MACHINE   MACHINE_TYPE_NAME("virt")
> @@ -266,9 +266,19 @@ static void fdt_add_psci_node(const VirtMachineState 
> *vms)
>      uint32_t migrate_fn;
>      void *fdt = vms->fdt;
>      ARMCPU *armcpu = ARM_CPU(qemu_get_cpu(0));
> +    const char *psci_method;
>  
> -    if (!vms->using_psci) {
> +    switch (vms->psci_conduit) {
> +    case QEMU_PSCI_CONDUIT_DISABLED:
>          return;
> +    case QEMU_PSCI_CONDUIT_HVC:
> +        psci_method = "hvc";
> +        break;
> +    case QEMU_PSCI_CONDUIT_SMC:
> +        psci_method = "smc";
> +        break;
> +    default:
> +        g_assert_not_reached();
>      }
>  
>      qemu_fdt_add_subnode(fdt, "/psci");
> @@ -300,7 +310,7 @@ static void fdt_add_psci_node(const VirtMachineState *vms)
>       * However, the device tree binding uses 'method' instead, so that is
>       * what we should use here.
>       */
> -    qemu_fdt_setprop_string(fdt, "/psci", "method", "hvc");
> +    qemu_fdt_setprop_string(fdt, "/psci", "method", psci_method);
>  
>      qemu_fdt_setprop_cell(fdt, "/psci", "cpu_suspend", cpu_suspend_fn);
>      qemu_fdt_setprop_cell(fdt, "/psci", "cpu_off", cpu_off_fn);
> @@ -402,7 +412,8 @@ static void fdt_add_cpu_nodes(const VirtMachineState *vms)
>          qemu_fdt_setprop_string(vms->fdt, nodename, "compatible",
>                                      armcpu->dtb_compatible);
>  
> -        if (vms->using_psci && vms->smp_cpus > 1) {
> +        if (vms->psci_conduit != QEMU_PSCI_CONDUIT_DISABLED
> +            && vms->smp_cpus > 1) {
>              qemu_fdt_setprop_string(vms->fdt, nodename,
>                                          "enable-method", "psci");
>          }
> @@ -1270,7 +1281,11 @@ static void machvirt_init(MachineState *machine)
>       * let the boot ROM sort them out.
>       * The usual case is that we do use QEMU's PSCI implementation.
>       */
> -    vms->using_psci = !(vms->secure && firmware_loaded);
> +    if (vms->secure && firmware_loaded) {
> +        vms->psci_conduit = QEMU_PSCI_CONDUIT_DISABLED;
> +    } else {
> +        vms->psci_conduit = QEMU_PSCI_CONDUIT_HVC;
> +    }
>  
>      /* The maximum number of CPUs depends on the GIC version, or on how
>       * many redistributors we can fit into the memory map.
> @@ -1353,8 +1368,8 @@ static void machvirt_init(MachineState *machine)
>              object_property_set_bool(cpuobj, false, "has_el3", NULL);
>          }
>  
> -        if (vms->using_psci) {
> -            object_property_set_int(cpuobj, QEMU_PSCI_CONDUIT_HVC,
> +        if (vms->psci_conduit != QEMU_PSCI_CONDUIT_DISABLED) {
> +            object_property_set_int(cpuobj, vms->psci_conduit,
>                                      "psci-conduit", NULL);
>  
>              /* Secondary CPUs start in PSCI powered-down state */
> -- 
> 2.7.4
>