Re: [PATCH v2] riscv: enable multi-range memory layout

Heinrich Schuchardt
2023-09-14T10:21:36Z

On 9/14/23 09:42, Wu, Fei wrote:
> On 9/14/2023 3:20 PM, Heinrich Schuchardt wrote:
>> On 9/14/23 08:48, Wu, Fei wrote:
>>> On 9/14/2023 2:05 PM, Heinrich Schuchardt wrote:
>>>>
>>>>
>>>> Am 14. September 2023 07:30:55 MESZ schrieb Fei Wu <fei2.wu@intel.com>:
>>>>> In order to enable PCIe passthrough on qemu riscv, the physical memory
>>>>> range between 3GB and 4GB is reserved. Therefore if guest has 4GB ram,
>>>>> two ranges are created as [2G, 3G) and [4G, 7G), currently u-boot sets
>>>>> ram_top to 4G - 1 if the gd->ram_top is above 4G in
>>>>
>>>> This should move to 7GiB - 1 in your example on riscv64.
>>>>
>>> I'm describing the current implementation of board_get_usable_ram_top()
>>> in ./arch/riscv/cpu/generic/dram.c. Do you mean this function should be
>>> changed? Is the comment about 32bit DMA device still valid?
>>>
>>> phys_size_t board_get_usable_ram_top(phys_size_t total_size)
>>> {
>>>          /*
>>>           * Ensure that we run from first 4GB so that all
>>>           * addresses used by U-Boot are 32bit addresses.
>>>           *
>>>           * This in-turn ensures that 32bit DMA capablehe
>>>           * devices work fine because DMA mapping APIs will
>>>           * provide 32bit DMA addresses only.
>>>           */
>>>          if (gd->ram_top >= SZ_4G)
>>>                  return SZ_4G - 1;
>>>
>>>          return gd->ram_top;
>>> }
>>
>> The comment above says 32bit DMA is board specific and not architecture
>> specific. So it is wrong to have this board_get_usable_ram_top()
>> function on architecture level. It makes usage of devices with all
>> memory above 4 GiB impossible.

@Anup:

The generic code was introduced by your patch 26f4fd1cb4f6 ("riscv:
generic: Ensure that U-Boot runs within 4GB for 64bit systems").

Which devices have that 32bit DMA issue?

fu540, fu740, jh7110 already have a cpu specific implementation and
don't need the generic one.

>>
>> It tried to pass through a SATA controller but received an error:
>>
>> # modprobe vfio-pci
>> # echo 0000:06:00.0 > /sys/bus/pci/drivers/ahci/unbind
>> # echo 1022 7091 > /sys/bus/pci/drivers/vfio-pci/new_id
>> # qemu-system-riscv64 -kernel u-boot.bin -nographic -M virt -m 4G
>> -device vfio-pci,host=0000:06:00.0
>> qemu-system-riscv64: -device vfio-pci,host=0000:06:00.0: VFIO_MAP_DMA
>> failed: Invalid argument
>> qemu-system-riscv64: -device vfio-pci,host=0000:06:00.0: vfio
>> 0000:06:00.0: failed to setup container for group 5: memory listener
>> initialization failed: Region riscv_virt_board.ram:
>> vfio_dma_map(0x55adbde66f70, 0x80000000, 0x100000000, 0x7fcd6fe00000) =
>> -22 (Invalid argument)
>>
>> With which version of QEMU were you able to use PCI pass through?
>>
> Please try this:
>
> base: ccb86f079a9e
> patch:
> https://lore.kernel.org/all/CAKmqyKMtAzt5saCUMd4vXYfgAQibpzQJAhtTSuSb+yeKhcYpfw@mail.gmail.com/T/

@Fei

With that patch I see the two memory banks in QEMU but when I attach a
vfio-pci device my whole system crashes and becomes unresponsive but
that is not a U-Boot issue.

Best regards

Heinrich

>
> Thanks,
> Fei.
>
>> Best regards
>>
>> Heinrich
>>
>>>
>>>>> board_get_usable_ram_top(), but that address is not backed by ram. This
>>>>> patch selects the lowest range instead.
>>>>>
>>>>> Signed-off-by: Fei Wu <fei2.wu@intel.com>
>>>>> ---
>>>>> arch/riscv/cpu/generic/dram.c        | 2 +-
>>>>> configs/qemu-riscv64_defconfig       | 2 +-
>>>>> configs/qemu-riscv64_smode_defconfig | 2 +-
>>>>> configs/qemu-riscv64_spl_defconfig   | 2 +-
>>>>> 4 files changed, 4 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/arch/riscv/cpu/generic/dram.c
>>>>> b/arch/riscv/cpu/generic/dram.c
>>>>> index 44e11bd56c..fb53a57b4e 100644
>>>>> --- a/arch/riscv/cpu/generic/dram.c
>>>>> +++ b/arch/riscv/cpu/generic/dram.c
>>>>> @@ -13,7 +13,7 @@ DECLARE_GLOBAL_DATA_PTR;
>>>>>
>>>>> int dram_init(void)
>>>>> {
>>>>> -    return fdtdec_setup_mem_size_base();
>>>>> +    return fdtdec_setup_mem_size_base_lowest();
>>>>
>>>> Linaro is working on allowing to download a distro image via https
>>>> and installing from a RAM disk.
>>>>
>>>> We should not artificially reduce the RAM size available for U-Boot
>>>> by restricting ourselfs to 1 GiB.
>>>>
>>>> We must ensure that ram top is in the upper range.
>>>>
>>> How do they handle the case of >4GB? board_get_usable_ram_top() attached
>>> above always returns <4GB. And it seems like
>>> fdtdec_setup_mem_size_base() cannot ensure the upper one is picked, it
>>> just picks up one, but which one is selected depending on fdt.
>>>
>>> Thanks,
>>> Fei.
>>>
>>>> Best regards
>>>>
>>>> Heinrich
>>>>
>>>>> }
>>>>>
>>>>> int dram_init_banksize(void)
>>>>> diff --git a/configs/qemu-riscv64_defconfig
>>>>> b/configs/qemu-riscv64_defconfig
>>>>> index 9a8bbef192..aa55317d26 100644
>>>>> --- a/configs/qemu-riscv64_defconfig
>>>>> +++ b/configs/qemu-riscv64_defconfig
>>>>> @@ -1,6 +1,6 @@
>>>>> CONFIG_RISCV=y
>>>>> CONFIG_SYS_MALLOC_LEN=0x800000
>>>>> -CONFIG_NR_DRAM_BANKS=1
>>>>> +CONFIG_NR_DRAM_BANKS=2
>>>>> CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
>>>>> CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
>>>>> CONFIG_ENV_SIZE=0x20000
>>>>> diff --git a/configs/qemu-riscv64_smode_defconfig
>>>>> b/configs/qemu-riscv64_smode_defconfig
>>>>> index 1d0f021ade..de08a49dab 100644
>>>>> --- a/configs/qemu-riscv64_smode_defconfig
>>>>> +++ b/configs/qemu-riscv64_smode_defconfig
>>>>> @@ -1,6 +1,6 @@
>>>>> CONFIG_RISCV=y
>>>>> CONFIG_SYS_MALLOC_LEN=0x800000
>>>>> -CONFIG_NR_DRAM_BANKS=1
>>>>> +CONFIG_NR_DRAM_BANKS=2
>>>>> CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
>>>>> CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
>>>>> CONFIG_ENV_SIZE=0x20000
>>>>> diff --git a/configs/qemu-riscv64_spl_defconfig
>>>>> b/configs/qemu-riscv64_spl_defconfig
>>>>> index bb10145e6e..66dc2a1dd9 100644
>>>>> --- a/configs/qemu-riscv64_spl_defconfig
>>>>> +++ b/configs/qemu-riscv64_spl_defconfig
>>>>> @@ -1,6 +1,6 @@
>>>>> CONFIG_RISCV=y
>>>>> CONFIG_SYS_MALLOC_LEN=0x800000
>>>>> -CONFIG_NR_DRAM_BANKS=1
>>>>> +CONFIG_NR_DRAM_BANKS=2
>>>>> CONFIG_HAS_CUSTOM_SYS_INIT_SP_ADDR=y
>>>>> CONFIG_CUSTOM_SYS_INIT_SP_ADDR=0x80200000
>>>>> CONFIG_ENV_SIZE=0x20000
>>>
>>
>