[SeaBIOS] Re: [PATCH 2/6] paravirt/qemu: virtio-mmio device discovery

[Kevin O'Connor]

On Thu, Mar 19, 2020 at 08:39:33AM +0100, Gerd Hoffmann wrote:
> Use bootorder fw_cfg file to find bootable virtio-mmio devices.
> Also add a new virtio-mmio.c source file, providing a function
> to register virtio-mmio devices.

Can you expand on this?  I'm not sure I understand what this patch
does.  It seems the bootorder file is used for device detection, but
that seems odd.

-Kevin
> Signed-off-by: Gerd Hoffmann
>
> Makefile             |  2 +-
>  src/hw/virtio-mmio.h |  6 ++++++
>  src/fw/paravirt.c    | 24 ++++++++++++++++++++++++
>  src/hw/virtio-mmio.c | 30 ++++++++++++++++++++++++++++++
>  4 files changed, 61 insertions(+), 1 deletion(-)
>  create mode 100644 src/hw/virtio-mmio.h
>  create mode 100644 src/hw/virtio-mmio.c
>
> diff --git a/Makefile b/Makefile
> index 5f7d5370198a..985ef591a13b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -43,7 +43,7 @@ SRC32FLAT=$(SRCBOTH) post.c e820map.c malloc.c romfile.c x86.c optionroms.c \
>      fw/coreboot.c fw/lzmadecode.c fw/multiboot.c fw/csm.c fw/biostables.c \
>      fw/paravirt.c fw/shadow.c fw/pciinit.c fw/smm.c fw/smp.c fw/mtrr.c fw/xen.c \
>      fw/acpi.c fw/mptable.c fw/pirtable.c fw/smbios.c fw/romfile_loader.c \
> hw/virtio-ring.c hw/virtio-pci.c hw/virtio-blk.c hw/virtio-scsi.c \
> hw/virtio-ring.c hw/virtio-pci.c hw/virtio-mmio.c hw/virtio-blk.c hw/virtio-scsi.c \
> hw/tpm_drivers.c hw/nvme.c
>
> SRC32SEG=string.c output.c pcibios.c apm.c stacks.c hw/pci.c hw/serialio.c
>  DIRS=src src/hw src/fw vgasrc
> diff --git a/src/hw/virtio-mmio.h b/src/hw/virtio-mmio.h
> new file mode 100644
> index 000000000000..751984241f49
> --- /dev/null
> +++ b/src/hw/virtio-mmio.h
> @@ -0,0 +1,6 @@
> +#ifndef _VIRTIO_MMIO_H
> +#define _VIRTIO_MMIO_H
>
> +void virtio_mmio_register(u64 mmio);
>
> +#endif /* _VIRTIO_MMIO_H */
> diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c
> index 119280c574fd..aaaf8b8dad31 100644
> --- a/src/fw/paravirt.c
> +++ b/src/fw/paravirt.c
> @@ -15,6 +15,7 @@
>  #include "hw/pcidevice.h" // pci_probe_devices
>  #include "hw/pci_regs.h" // PCI_DEVICE_ID
>  #include "hw/serialio.h" // PORT_SERIAL1
> +#include "hw/virtio-mmio.h" // virtio_mmio_register
>  #include "hw/rtc.h" // CMOS_*
>  #include "malloc.h" // malloc_tmp
>  #include "output.h" // dprintf
> @@ -192,6 +193,27 @@ static void msr_feature_control_setup(void)
>          wrmsr_smp(MSR_IA32_FEATURE_CONTROL, feature_control_bits);
>  }
>
> +static void qemu_probe_virtio_mmio(void)
> +{
> char *data, *next;
> int size;
> u64 mmio;
> data = romfile_loadfile("bootorder", &size);
> while (data) {
>    next = strchr(data, '\n');
>    if (next) {
>        *next = '\0';
>        next++;
>    }
>    if (memcmp("/virtio-mmio@", data, 13) == 0) {
>        mmio = strtol(data+13, 16);
>        virtio_mmio_register(mmio);
>    }
>    data = next;
> }
>
> +}
>
> void
>  qemu_platform_setup(void)
>  {
> @@ -217,6 +239,8 @@ qemu_platform_setup(void)
>      msr_feature_control_setup();
>      smp_setup();
> qemu_probe_virtio_mmio();
> // Create bios tables
>    if (MaxCountCPUs <= 255) {
>        pirtable_setup();
>
> diff --git a/src/hw/virtio-mmio.c b/src/hw/virtio-mmio.c
> new file mode 100644
> index 000000000000..0f320921df30
> --- /dev/null
> +++ b/src/hw/virtio-mmio.c
> @@ -0,0 +1,30 @@
> +#include "config.h" // CONFIG_DEBUG_LEVEL
> +#include "malloc.h" // free
> +#include "output.h" // dprintf
> +#include "virtio-pci.h"
> +#include "virtio-ring.h"
>
> +/* qemu microvm supports 8 virtio-mmio devices */
> +static u64 devs[8];
>
> +void virtio_mmio_register(u64 mmio)
> +{
> int i;
> for (i = 0; i < ARRAY_SIZE(devs); i++) {
>    if (devs[i] == mmio) {
>        /*
>         * This can happen in case we have multiple scsi devices
>         * attached to a single virtio-scsi controller
>         */
>        dprintf(3, "virtio-mmio: duplicate device at 0x%llx, ignoring\n", mmio);
>        return;
>    }
>    if (devs[i] == 0) {
>        dprintf(1, "virtio-mmio: device at 0x%llx\n", mmio);
>        devs[i] = mmio;
>        return;
>    }
> }
> dprintf(1, "virtio-mmio: device list full\n");
> +}
>
> 2.18.2
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