Re: [PATCH v3 2/3] hw/tpm: gate PPI support on tpm-tis-device behind a device property

[Stefan Berger <stefanb@linux.ibm.com>]

On 6/19/26 5:31 AM, Mohammadfaiz Bawa wrote:
> Add a "ppi" boolean property (default: true) to tpm-tis-device.
> When ppi=off the RAMBlock is never registered and the migration
> stream omits "tpm-ppi", restoring backward compatibility.
> 
> Move sysbus_init_mmio() calls from instance_init to realizefn so
> the memory regions are initialized before being registered.  When
> ppi=off, the PPI MMIO region is simply not exposed.
> 
> Fixes: 46cd2c1050f0 ("hw/tpm: add PPI support to tpm-tis-device for ARM64 virt")
> Signed-off-by: Mohammadfaiz Bawa <mbawa@redhat.com>
> ---
>   hw/tpm/tpm_tis.h        |  1 +
>   hw/tpm/tpm_tis_sysbus.c | 18 +++++++++++-------
>   2 files changed, 12 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/tpm/tpm_tis.h b/hw/tpm/tpm_tis.h
> index 1531620bf9..6ac9804050 100644
> --- a/hw/tpm/tpm_tis.h
> +++ b/hw/tpm/tpm_tis.h
> @@ -76,6 +76,7 @@ typedef struct TPMState {
>       size_t be_buffer_size;
>   
>       TPMPPI ppi;
> +    bool ppi_enabled;
>   } TPMState;
>   
>   extern const VMStateDescription vmstate_locty;
> diff --git a/hw/tpm/tpm_tis_sysbus.c b/hw/tpm/tpm_tis_sysbus.c
> index 16bb17874b..a7b0002d82 100644
> --- a/hw/tpm/tpm_tis_sysbus.c
> +++ b/hw/tpm/tpm_tis_sysbus.c
> @@ -94,6 +94,7 @@ static void tpm_tis_sysbus_reset(DeviceState *dev)
>   static const Property tpm_tis_sysbus_properties[] = {
>       DEFINE_PROP_UINT32("irq", TPMStateSysBus, state.irq_num, TPM_TIS_IRQ),
>       DEFINE_PROP_TPMBE("tpmdev", TPMStateSysBus, state.be_driver),
> +    DEFINE_PROP_BOOL("ppi", TPMStateSysBus, state.ppi_enabled, true),
>   };
>   
>   static void tpm_tis_sysbus_initfn(Object *obj)
> @@ -101,9 +102,7 @@ static void tpm_tis_sysbus_initfn(Object *obj)
>       TPMStateSysBus *sbdev = TPM_TIS_SYSBUS(obj);
>       TPMState *s = &sbdev->state;
>   
> -    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->mmio);
>       sysbus_init_irq(SYS_BUS_DEVICE(obj), &s->irq);
> -    sysbus_init_mmio(SYS_BUS_DEVICE(obj), &s->ppi.ram);
>   }
>   
>   static void tpm_tis_sysbus_realizefn(DeviceState *dev, Error **errp)
> @@ -122,14 +121,19 @@ static void tpm_tis_sysbus_realizefn(DeviceState *dev, Error **errp)
>           return;
>       }
>   
> -    s->ppi.buf = qemu_memalign(host_page_size,
> -                               ROUND_UP(TPM_PPI_ADDR_SIZE, host_page_size));
>       memory_region_init_io(&s->mmio, OBJECT(dev), &tpm_tis_memory_ops,
>                             s, "tpm-tis-mmio",
>                             TPM_TIS_NUM_LOCALITIES << TPM_TIS_LOCALITY_SHIFT);
> -    memory_region_init_ram_device_ptr(&s->ppi.ram, OBJECT(dev), "tpm-ppi",
> -                                      TPM_PPI_ADDR_SIZE, s->ppi.buf);
> -    vmstate_register_ram(&s->ppi.ram, dev);
> +    sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->mmio);
> +
> +    if (s->ppi_enabled) {
> +        s->ppi.buf = qemu_memalign(host_page_size,
> +                                   ROUND_UP(TPM_PPI_ADDR_SIZE, host_page_size));
> +        memory_region_init_ram_device_ptr(&s->ppi.ram, OBJECT(dev), "tpm-ppi",
> +                                          TPM_PPI_ADDR_SIZE, s->ppi.buf);
> +        sysbus_init_mmio(SYS_BUS_DEVICE(dev), &s->ppi.ram);
> +        vmstate_register_ram(&s->ppi.ram, dev);
> +    }
>   }
>   
>   static void tpm_tis_sysbus_class_init(ObjectClass *klass, const void *data)

Reviewed-by: Stefan Berger <stefanb@linux.ibm.com>