On Fri, Nov 28, 2014 at 11:49:48AM +0100, Laszlo Ersek wrote: > On 11/28/14 11:43, 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? > > > > 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.) > > > > The full register block is 3 bytes wide. Is that a problem? > > Hm, I think I get it now. If FW_CFG_DATA_SIZE were to increase, then its > alignment would have to increase as well, and whatever alignment > FW_CFG_SIZE provides might not suffice. So, you'd calculate the natural > alignment, but wouldn't increase it beyond 4. > > I do think this is a bit overkill :) but I can do it. Let's wait for > more review comments first.
Actually, on second thought, completely scratch my overkill suggestion. It's actually wrong to be concerned with it anyway. FW_CFG_DATA_SIZE doesn't dictate how we should access the data port, the fw-cfg protocol does, and that says we should access exactly one byte. So, regardless of the fw-cfg-data size, we'll never have to worry about the data port's alignment, as we'll never access more than one byte from it. > > Thanks! > Laszlo