On 3/27/25 13:24, Philippe Mathieu-Daudé wrote:
On 25/3/25 23:44, Richard Henderson wrote:
If i/o does not cover the entire first page, allocate a portion
of ram as an i/o device, so that the entire first page is i/o.
While memory_region_init_ram_device_ptr is happy to allocate
the RAMBlock, it does not register the ram for migration.
Do this by hand.
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
---
hw/avr/atmega.h | 1 +
hw/avr/atmega.c | 39 ++++++++++++++++++++++++++++++++-------
2 files changed, 33 insertions(+), 7 deletions(-)
diff --git a/hw/avr/atmega.h b/hw/avr/atmega.h
index a99ee15c7e..9ac4678231 100644
--- a/hw/avr/atmega.h
+++ b/hw/avr/atmega.h
@@ -41,6 +41,7 @@ struct AtmegaMcuState {
MemoryRegion flash;
MemoryRegion eeprom;
MemoryRegion sram;
+ MemoryRegion sram_io;
DeviceState *io;
AVRMaskState pwr[POWER_MAX];
AVRUsartState usart[USART_MAX];
@@ -240,11 +239,37 @@ static void atmega_realize(DeviceState *dev, Error **errp)
qdev_realize(DEVICE(&s->cpu), NULL, &error_abort);
cpudev = DEVICE(&s->cpu);
- /* SRAM */
- memory_region_init_ram(&s->sram, OBJECT(dev), "sram", mc->sram_size,
- &error_abort);
- memory_region_add_subregion(get_system_memory(),
- OFFSET_DATA + mc->io_size, &s->sram);
+ /*
+ * SRAM
+ *
+ * Softmmu is not able mix i/o and ram on the same page.
+ * Therefore in all cases, the first page exclusively contains i/o.
+ *
+ * If the MCU's i/o region matches the page size, then we can simply
+ * allocate all ram starting at the second page. Otherwise, we must
+ * allocate some ram as i/o to complete the first page.
+ */
+ assert(mc->io_size == 0x100 || mc->io_size == 0x200);
+ if (mc->io_size >= TARGET_PAGE_SIZE) {
+ memory_region_init_ram(&s->sram, OBJECT(dev), "sram", mc->sram_size,
+ &error_abort);
+ memory_region_add_subregion(get_system_memory(),
+ OFFSET_DATA + mc->io_size, &s->sram);
+ } else {
+ int sram_io_size = TARGET_PAGE_SIZE - mc->io_size;
+ void *sram_io_mem = g_malloc0(sram_io_size);
Please declare sram_io_mem in AtmegaMcuState, after sram_io.
Why?
+
+ memory_region_init_ram_device_ptr(&s->sram_io, OBJECT(dev),
"sram-as-io",
+ sram_io_size, sram_io_mem);
After this, it's accessible as
s->sram_io->ram_block->host
It wouldn't be accessed in any other way, surely?
r~
