On Fri, Nov 28, 2014 at 11:43:32AM +0100, Laszlo Ersek wrote: > On 11/28/14 11:38, Andrew Jones wrote: > > On Fri, Nov 28, 2014 at 12:18:27AM +0100, Laszlo Ersek wrote: > >> 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. > >> > >> 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. > >> > >> 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> > >> --- > >> hw/arm/virt.c | 21 +++++++++++++++++++++ > >> 1 file changed, 21 insertions(+) > >> > >> diff --git a/hw/arm/virt.c b/hw/arm/virt.c > >> index 314e55b..070bd34 100644 > >> --- a/hw/arm/virt.c > >> +++ b/hw/arm/virt.c > >> @@ -68,6 +68,7 @@ enum { > >> VIRT_UART, > >> VIRT_MMIO, > >> VIRT_RTC, > >> + VIRT_FW_CFG, > >> }; > >> > >> typedef struct MemMapEntry { > >> @@ -107,6 +108,7 @@ static const MemMapEntry a15memmap[] = { > >> [VIRT_GIC_CPU] = { 0x08010000, 0x00010000 }, > >> [VIRT_UART] = { 0x09000000, 0x00001000 }, > >> [VIRT_RTC] = { 0x09010000, 0x00001000 }, > >> + [VIRT_FW_CFG] = { 0x09020000, FW_CFG_SIZE + FW_CFG_DATA_SIZE }, > >> [VIRT_MMIO] = { 0x0a000000, 0x00000200 }, > >> /* ...repeating for a total of NUM_VIRTIO_TRANSPORTS, each of that > >> size */ > >> /* 0x10000000 .. 0x40000000 reserved for PCI */ > >> @@ -519,6 +521,23 @@ static void create_flash(const VirtBoardInfo *vbi) > >> g_free(nodename); > >> } > >> > >> +static void create_fw_cfg(const VirtBoardInfo *vbi) > >> +{ > >> + hwaddr base = vbi->memmap[VIRT_FW_CFG].base; > >> + char *nodename; > >> + > >> + fw_cfg_init(0, 0, base, base + FW_CFG_SIZE); > >> + > >> + nodename = g_strdup_printf("/fw-cfg@%" PRIx64, base); > >> + qemu_fdt_add_subnode(vbi->fdt, nodename); > >> + qemu_fdt_setprop_string(vbi->fdt, nodename, > >> + "compatible", "fw-cfg,mmio"); > >> + qemu_fdt_setprop_sized_cells(vbi->fdt, nodename, "reg", > >> + 2, base, 2, FW_CFG_SIZE, > >> + 2, base + FW_CFG_SIZE, 2, > >> FW_CFG_DATA_SIZE); > > > > Overkill suggestion alert, but how about defining something like > > > > #define FW_CFG_SIZE_ALIGNED \ > > MIN(QEMU_ALIGN_UP(FW_CFG_SIZE, FW_CFG_DATA_SIZE), \ > > QEMU_ALIGN_UP(FW_CFG_SIZE, 4)) > > > > and then using that in your memmap size calculation and fw-cfg-data base > > address calculation. The only reason I suggest this is because it's hard > > to tell that fw-cfg-data's address will be naturally aligned without > > hunting down the definition of FW_CFG_DATA_SIZE. And, if it were to change > > (which it probably never will), then it may not be. > > Why does it need to be aligned?
Natural alignment is more efficient. > > The selector register is aligned at a 64KB boundary (for independent, > strict reasons). > > The data register is not aligned at all, and -- AFAICS -- it need not > be, because it's 1 byte wide. (In fact the ARM-specific > Mmio(Read|Write)XX functions in edk2 enforce natural alignment, and the > above layout passes without problems.) Right. As FW_CFG_DATA_SIZE is currently 1 byte, it's already naturally aligned, and the macro definition I have above actually doesn't change anything (which is why I gave the overkill alert). However if FW_CFG_DATA_SIZE was to change, then the natural alignment could be lost. > > The full register block is 3 bytes wide. Is that a problem? No, it's fine as is, and the FW_CFG_SIZE_ALIGNED would leave it 3 bytes wide too. FW_CFG_SIZE_ALIGNED only adds future-proofing. However it really is overkill as the chance that FW_CFG_DATA_SIZE will change is nil. > > Thanks > Laszlo > > > > >> + g_free(nodename); > >> +} > >> + > >> static void *machvirt_dtb(const struct arm_boot_info *binfo, int > >> *fdt_size) > >> { > >> const VirtBoardInfo *board = (const VirtBoardInfo *)binfo; > >> @@ -604,6 +623,8 @@ static void machvirt_init(MachineState *machine) > >> */ > >> 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; > >> -- > >> 1.8.3.1 > >> >