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

["Wu, Fei" <fei2.wu@intel.com>]

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 capable
>>           * 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.
> 
> 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/

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
>>
>