Re: [Qemu-devel] [PATCH v2 2/2] hw/arm/virt: Provide PL031 RTC

[Claudio Fontana <claudio.fontana@huawei.com>]

On 10.06.2014 19:06, Peter Maydell wrote:
> UEFI mandates that the platform must include an RTC, so provide
> one in 'virt', using the PL031.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>  hw/arm/virt.c | 30 ++++++++++++++++++++++++++++++
>  1 file changed, 30 insertions(+)
> 
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index e658eb0..b60928e 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -66,6 +66,7 @@ enum {
>      VIRT_GIC_CPU,
>      VIRT_UART,
>      VIRT_MMIO,
> +    VIRT_RTC,
>  };
>  
>  typedef struct MemMapEntry {
> @@ -93,6 +94,8 @@ typedef struct VirtBoardInfo {
>   * high memory region beyond 4GB).
>   * This represents a compromise between how much RAM can be given to
>   * a 32 bit VM and leaving space for expansion and in particular for PCI.
> + * Note that devices should generally be placed at multiples of 0x10000,
> + * to accommodate guests using 64K pages.
>   */
>  static const MemMapEntry a15memmap[] = {
>      [VIRT_FLASH] = { 0, 0x8000000 },
> @@ -101,6 +104,7 @@ static const MemMapEntry a15memmap[] = {
>      [VIRT_GIC_DIST] = { 0x8000000, 0x10000 },
>      [VIRT_GIC_CPU] = { 0x8010000, 0x10000 },
>      [VIRT_UART] = { 0x9000000, 0x1000 },
> +    [VIRT_RTC] = { 0x90010000, 0x1000 },
>      [VIRT_MMIO] = { 0xa000000, 0x200 },
>      /* ...repeating for a total of NUM_VIRTIO_TRANSPORTS, each of that size */
>      /* 0x10000000 .. 0x40000000 reserved for PCI */
> @@ -109,6 +113,7 @@ static const MemMapEntry a15memmap[] = {
>  
>  static const int a15irqmap[] = {
>      [VIRT_UART] = 1,
> +    [VIRT_RTC] = 2,
>      [VIRT_MMIO] = 16, /* ...to 16 + NUM_VIRTIO_TRANSPORTS - 1 */
>  };
>  
> @@ -340,6 +345,29 @@ static void create_uart(const VirtBoardInfo *vbi, qemu_irq *pic)
>      g_free(nodename);
>  }
>  
> +static void create_rtc(const VirtBoardInfo *vbi, qemu_irq *pic)
> +{
> +    char *nodename;
> +    hwaddr base = vbi->memmap[VIRT_RTC].base;
> +    hwaddr size = vbi->memmap[VIRT_RTC].size;
> +    int irq = vbi->irqmap[VIRT_RTC];
> +    const char compat[] = "arm,pl031\0arm,primecell";
> +
> +    sysbus_create_simple("pl031", base, pic[irq]);
> +
> +    nodename = g_strdup_printf("/pl031@%" PRIx64, base);
> +    qemu_fdt_add_subnode(vbi->fdt, nodename);
> +    qemu_fdt_setprop(vbi->fdt, nodename, "compatible", compat, sizeof(compat));
> +    qemu_fdt_setprop_sized_cells(vbi->fdt, nodename, "reg",
> +                                 2, base, 2, size);
> +    qemu_fdt_setprop_cells(vbi->fdt, nodename, "interrupts",
> +                           GIC_FDT_IRQ_TYPE_SPI, irq,
> +                           GIC_FDT_IRQ_FLAGS_EDGE_LO_HI);
> +    qemu_fdt_setprop_cell(vbi->fdt, nodename, "clocks", vbi->clock_phandle);
> +    qemu_fdt_setprop_string(vbi->fdt, nodename, "clock-names", "apb_pclk");
> +    g_free(nodename);
> +}
> +
>  static void create_virtio_devices(const VirtBoardInfo *vbi, qemu_irq *pic)
>  {
>      int i;
> @@ -524,6 +552,8 @@ static void machvirt_init(MachineState *machine)
>  
>      create_uart(vbi, pic);
>  
> +    create_rtc(vbi, pic);
> +
>      /* Create mmio transports, so the user can create virtio backends
>       * (which will be automatically plugged in to the transports). If
>       * no backend is created the transport will just sit harmlessly idle.
> 

I am quite happy with the RTC device being added to the virt platform, as this will move me from 1970 in the guest, where I am at the moment. :)

One question I would have is, what would be the best/recommended way as a user of the virt platform
to add buses and devices to the platform? Is using virt as the base platform, and extending it with additional buses and devices a sensible thing to do?

In my case I am particularly interested in the possibility to add a PCI-E bus to the platform in some (any) way, so that QEMU provides support for that, one that does not mean maintaining a separate patchset. Is extending via --device a viable option?
New machine model?

Thank you for any advice,

Claudio