Re: [PATCH v1 10/12] hw/arm: introduce xenpv machine

[Julien Grall <julien@xen.org>]

Hi,

On 27/10/2022 09:02, Alex Bennée wrote:
> 
> Vikram Garhwal <vikram.garhwal@amd.com> writes:
> 
> <snip>
>> Optional: When CONFIG_TPM is enabled, it also creates a tpm-tis-device, adds a
>> TPM emulator and connects to swtpm running on host machine via chardev socket
>> and support TPM functionalities for a guest domain.
>>
>> Extra command line for aarch64 xenpv QEMU to connect to swtpm:
>>      -chardev socket,id=chrtpm,path=/tmp/myvtpm2/swtpm-sock \
>>      -tpmdev emulator,id=tpm0,chardev=chrtpm \
>>
>> swtpm implements a TPM software emulator(TPM 1.2 & TPM 2) built on libtpms and
>> provides access to TPM functionality over socket, chardev and CUSE interface.
>> Github repo: https://github.com/stefanberger/swtpm
>> Example for starting swtpm on host machine:
>>      mkdir /tmp/vtpm2
>>      swtpm socket --tpmstate dir=/tmp/vtpm2 \
>>      --ctrl type=unixio,path=/tmp/vtpm2/swtpm-sock &
> 
> <snip>
>> +static void xen_enable_tpm(void)
>> +{
>> +/* qemu_find_tpm_be is only available when CONFIG_TPM is enabled. */
>> +#ifdef CONFIG_TPM
>> +    Error *errp = NULL;
>> +    DeviceState *dev;
>> +    SysBusDevice *busdev;
>> +
>> +    TPMBackend *be = qemu_find_tpm_be("tpm0");
>> +    if (be == NULL) {
>> +        DPRINTF("Couldn't fine the backend for tpm0\n");
>> +        return;
>> +    }
>> +    dev = qdev_new(TYPE_TPM_TIS_SYSBUS);
>> +    object_property_set_link(OBJECT(dev), "tpmdev", OBJECT(be), &errp);
>> +    object_property_set_str(OBJECT(dev), "tpmdev", be->id, &errp);
>> +    busdev = SYS_BUS_DEVICE(dev);
>> +    sysbus_realize_and_unref(busdev, &error_fatal);
>> +    sysbus_mmio_map(busdev, 0, GUEST_TPM_BASE);
> 
> I'm not sure what has gone wrong here but I'm getting:
> 
>    ../../hw/arm/xen_arm.c: In function ‘xen_enable_tpm’:
>    ../../hw/arm/xen_arm.c:120:32: error: ‘GUEST_TPM_BASE’ undeclared (first use in this function); did you mean ‘GUEST_RAM_BASE’?
>      120 |     sysbus_mmio_map(busdev, 0, GUEST_TPM_BASE);
>          |                                ^~~~~~~~~~~~~~
>          |                                GUEST_RAM_BASE
>    ../../hw/arm/xen_arm.c:120:32: note: each undeclared identifier is reported only once for each function it appears in
> 
> In my cross build:
> 
>    # Configured with: '../../configure' '--disable-docs' '--target-list=aarch64-softmmu' '--disable-kvm' '--enable-xen' '--disable-opengl' '--disable-libudev' '--enable-tpm' '--disable-xen-pci-passthrough' '--cross-prefix=aarch64-linux-gnu-' '--skip-meson'
> 
> which makes me wonder if this is a configure failure or a confusion
> about being able to have host swtpm implementations during emulation but
> needing target tpm for Xen?

I was also wondering where is that value come from. Note that the 
memory/IRQ layout exposed to the guest is not stable.

Are we expecting the user to rebuild QEMU for every Xen versions (or 
possibly every guest if we ever allow dynamic layout in Xen)?

Cheers,

-- 
Julien Grall