fw_cfg already supports exposure over MMIO (used in ppc/mac_newworld.c, ppc/mac_oldworld.c, sparc/sun4m.c); we can easily add it to the "virt" board.
Because MMIO access is slow on ARM KVM, we enable the guest, with fw_cfg_init_data_memwidth(), to transfer up to 8 bytes with a single access. This has been measured to speed up transfers up to 7.5-fold, relative to single byte data access, on both ARM KVM and x86_64 TCG. The mmio register block of fw_cfg is advertized in the device tree. As base address we pick 0x09020000, which conforms to the comment preceding "a15memmap": it falls in the miscellaneous device I/O range 128MB..256MB, and it is aligned at 64KB. The DTB properties follow the documentation in the Linux source file "Documentation/devicetree/bindings/arm/fw-cfg.txt". fw_cfg automatically exports a number of files to the guest; for example, "bootorder" (see fw_cfg_machine_reset()). Signed-off-by: Laszlo Ersek <ler...@redhat.com> --- Notes: v3: - enable 8-byte wide access to fw_cfg MMIO data port [Drew] - expose the exact size of the fused region in the DTB [Peter] - reorder data register and control register so that we can keep the region contiguous and still conform to alignment requirements [Laszlo] hw/arm/virt.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) diff --git a/hw/arm/virt.c b/hw/arm/virt.c index 314e55b..274aaae 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -67,8 +67,9 @@ enum { VIRT_GIC_CPU, VIRT_UART, VIRT_MMIO, VIRT_RTC, + VIRT_FW_CFG, }; typedef struct MemMapEntry { hwaddr base; @@ -106,8 +107,9 @@ static const MemMapEntry a15memmap[] = { [VIRT_GIC_DIST] = { 0x08000000, 0x00010000 }, [VIRT_GIC_CPU] = { 0x08010000, 0x00010000 }, [VIRT_UART] = { 0x09000000, 0x00001000 }, [VIRT_RTC] = { 0x09010000, 0x00001000 }, + [VIRT_FW_CFG] = { 0x09020000, 0x0000000a }, [VIRT_MMIO] = { 0x0a000000, 0x00000200 }, /* ...repeating for a total of NUM_VIRTIO_TRANSPORTS, each of that size */ /* 0x10000000 .. 0x40000000 reserved for PCI */ [VIRT_MEM] = { 0x40000000, 30ULL * 1024 * 1024 * 1024 }, @@ -518,8 +520,25 @@ static void create_flash(const VirtBoardInfo *vbi) qemu_fdt_setprop_cell(vbi->fdt, nodename, "bank-width", 4); g_free(nodename); } +static void create_fw_cfg(const VirtBoardInfo *vbi) +{ + hwaddr base = vbi->memmap[VIRT_FW_CFG].base; + hwaddr size = vbi->memmap[VIRT_FW_CFG].size; + char *nodename; + + fw_cfg_init_data_memwidth(0, 0, base + 8, base, 8); + + nodename = g_strdup_printf("/fw-cfg@%" PRIx64, base); + qemu_fdt_add_subnode(vbi->fdt, nodename); + qemu_fdt_setprop_string(vbi->fdt, nodename, + "compatible", "qemu,fw-cfg-mmio"); + qemu_fdt_setprop_sized_cells(vbi->fdt, nodename, "reg", + 2, base, 2, size); + g_free(nodename); +} + static void *machvirt_dtb(const struct arm_boot_info *binfo, int *fdt_size) { const VirtBoardInfo *board = (const VirtBoardInfo *)binfo; @@ -603,8 +622,10 @@ static void machvirt_init(MachineState *machine) * no backend is created the transport will just sit harmlessly idle. */ create_virtio_devices(vbi, pic); + create_fw_cfg(vbi); + vbi->bootinfo.ram_size = machine->ram_size; vbi->bootinfo.kernel_filename = machine->kernel_filename; vbi->bootinfo.kernel_cmdline = machine->kernel_cmdline; vbi->bootinfo.initrd_filename = machine->initrd_filename; -- 1.8.3.1