[PATCH] gpu: nova-core: depend on CONFIG_64BIT

[PATCH] gpu: nova-core: depend on CONFIG_64BIT

[Danilo Krummrich]

If built on architectures with CONFIG_ARCH_DMA_ADDR_T_64BIT=y nova-core
produces that following build failures:

    error[E0308]: mismatched types
      --> drivers/gpu/nova-core/fb.rs:49:59
       |
    49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle())?;
       |                              -----------------------      ^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
       |                              |
       |                              arguments to this method are incorrect
       |
    note: method defined here
      --> drivers/gpu/nova-core/fb/hal.rs:19:8
       |
    19 |     fn write_sysmem_flush_page(&self, bar: &Bar0, addr: u64) -> Result;
       |        ^^^^^^^^^^^^^^^^^^^^^^^
    help: you can convert a `u32` to a `u64`
       |
    49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle().into())?;
       |                                                                            +++++++

    error[E0308]: mismatched types
      --> drivers/gpu/nova-core/fb.rs:65:47
       |
    65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle() {
       |            -------------------------------    ^^^^^^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
       |            |
       |            expected because this is `u64`
       |
    help: you can convert a `u32` to a `u64`
       |
    65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle().into() {
       |                                                                     +++++++

    error: this arithmetic operation will overflow
       --> drivers/gpu/nova-core/falcon.rs:469:23
        |
    469 |             .set_base((dma_start >> 40) as u16)
        |                       ^^^^^^^^^^^^^^^^^ attempt to shift right by `40_i32`, which would overflow
        |
        = note: `#[deny(arithmetic_overflow)]` on by default

This is due to the code making assumptions on the width of dma_addr_t to
be 64 bit.

While this could technically be handled, it is rather painful to deal
with, as the following example illustrates:

	pub(super) fn read_sysmem_flush_page_ga100(bar: &Bar0) -> DmaAddress {
	    let addr = u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR::read(bar).adr_39_08())
	        << FLUSH_SYSMEM_ADDR_SHIFT
	        | u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI::read(bar).adr_63_40())
	            << FLUSH_SYSMEM_ADDR_SHIFT_HI;

	    addr.try_into().unwrap_or_else(|_| {
	        kernel::warn_on!(true);

	        0
	    })
	}

At the same time there's not much value for nova-core to support 32-bit,
given that the supported GPU architectures are Turing and later, hence
depend on CONFIG_64BIT.

Cc: John Hubbard <jhubbard@nvidia.com>
Reported-by: Miguel Ojeda <ojeda@kernel.org>
Closes: https://lore.kernel.org/lkml/20250828160247.37492-1-ojeda@kernel.org/
Fixes: 6554ad65b589 ("gpu: nova-core: register sysmem flush page")
Fixes: 69f5cd67ce41 ("gpu: nova-core: add falcon register definitions and base code")
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
---
 drivers/gpu/nova-core/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
index 8726d80d6ba4..20d3e6d0d796 100644
--- a/drivers/gpu/nova-core/Kconfig
+++ b/drivers/gpu/nova-core/Kconfig
@@ -1,5 +1,6 @@
 config NOVA_CORE
 	tristate "Nova Core GPU driver"
+	depends on 64BIT
 	depends on PCI
 	depends on RUST
 	depends on RUST_FW_LOADER_ABSTRACTIONS

base-commit: 1b237f190eb3d36f52dffe07a40b5eb210280e00
-- 
2.51.0

Re: [PATCH] gpu: nova-core: depend on CONFIG_64BIT

[John Hubbard]

On 8/28/25 3:39 PM, Danilo Krummrich wrote:
...
> diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
> index 8726d80d6ba4..20d3e6d0d796 100644
> --- a/drivers/gpu/nova-core/Kconfig
> +++ b/drivers/gpu/nova-core/Kconfig
> @@ -1,5 +1,6 @@
>  config NOVA_CORE
>  	tristate "Nova Core GPU driver"
> +	depends on 64BIT

Yes!

Reviewed-by: John Hubbard <jhubbard@nvidia.com>

thanks,
-- 
John Hubbard

Re: [PATCH] gpu: nova-core: depend on CONFIG_64BIT

[Alexandre Courbot]

On Fri Aug 29, 2025 at 7:39 AM JST, Danilo Krummrich wrote:
> If built on architectures with CONFIG_ARCH_DMA_ADDR_T_64BIT=y nova-core
> produces that following build failures:
>
>     error[E0308]: mismatched types
>       --> drivers/gpu/nova-core/fb.rs:49:59
>        |
>     49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle())?;
>        |                              -----------------------      ^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
>        |                              |
>        |                              arguments to this method are incorrect
>        |
>     note: method defined here
>       --> drivers/gpu/nova-core/fb/hal.rs:19:8
>        |
>     19 |     fn write_sysmem_flush_page(&self, bar: &Bar0, addr: u64) -> Result;
>        |        ^^^^^^^^^^^^^^^^^^^^^^^
>     help: you can convert a `u32` to a `u64`
>        |
>     49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle().into())?;
>        |                                                                            +++++++
>
>     error[E0308]: mismatched types
>       --> drivers/gpu/nova-core/fb.rs:65:47
>        |
>     65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle() {
>        |            -------------------------------    ^^^^^^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
>        |            |
>        |            expected because this is `u64`
>        |
>     help: you can convert a `u32` to a `u64`
>        |
>     65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle().into() {
>        |                                                                     +++++++
>
>     error: this arithmetic operation will overflow
>        --> drivers/gpu/nova-core/falcon.rs:469:23
>         |
>     469 |             .set_base((dma_start >> 40) as u16)
>         |                       ^^^^^^^^^^^^^^^^^ attempt to shift right by `40_i32`, which would overflow
>         |
>         = note: `#[deny(arithmetic_overflow)]` on by default
>
> This is due to the code making assumptions on the width of dma_addr_t to
> be 64 bit.
>
> While this could technically be handled, it is rather painful to deal
> with, as the following example illustrates:
>
> 	pub(super) fn read_sysmem_flush_page_ga100(bar: &Bar0) -> DmaAddress {
> 	    let addr = u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR::read(bar).adr_39_08())
> 	        << FLUSH_SYSMEM_ADDR_SHIFT
> 	        | u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI::read(bar).adr_63_40())
> 	            << FLUSH_SYSMEM_ADDR_SHIFT_HI;
>
> 	    addr.try_into().unwrap_or_else(|_| {
> 	        kernel::warn_on!(true);
>
> 	        0
> 	    })
> 	}
>
> At the same time there's not much value for nova-core to support 32-bit,
> given that the supported GPU architectures are Turing and later, hence
> depend on CONFIG_64BIT.
>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Reported-by: Miguel Ojeda <ojeda@kernel.org>
> Closes: https://lore.kernel.org/lkml/20250828160247.37492-1-ojeda@kernel.org/
> Fixes: 6554ad65b589 ("gpu: nova-core: register sysmem flush page")
> Fixes: 69f5cd67ce41 ("gpu: nova-core: add falcon register definitions and base code")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Thanks!

Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>

Re: [PATCH] gpu: nova-core: depend on CONFIG_64BIT

[Alexandre Courbot]

On Fri Aug 29, 2025 at 7:39 AM JST, Danilo Krummrich wrote:
<snip>
> diff --git a/drivers/gpu/nova-core/Kconfig b/drivers/gpu/nova-core/Kconfig
> index 8726d80d6ba4..20d3e6d0d796 100644
> --- a/drivers/gpu/nova-core/Kconfig
> +++ b/drivers/gpu/nova-core/Kconfig
> @@ -1,5 +1,6 @@
>  config NOVA_CORE
>  	tristate "Nova Core GPU driver"
> +	depends on 64BIT
>  	depends on PCI
>  	depends on RUST
>  	depends on RUST_FW_LOADER_ABSTRACTIONS

Another thing we probably want to depend on: a little-endian
architecture. There is an assumption in the code that the CPU will use
this endianness, and while it can be changed to be more portable, this
would require stuff like proc-macros to properly build a struct from a
data stream with endianness in mind, which we don't have yet.

Most (all?) the platforms on which NVIDIA GPUs are to run are
little-endian anyway, so I am not even sure big-endian support would be
useful.

Re: [PATCH] gpu: nova-core: depend on CONFIG_64BIT

[Danilo Krummrich]

On Fri Aug 29, 2025 at 12:39 AM CEST, Danilo Krummrich wrote:
> If built on architectures with CONFIG_ARCH_DMA_ADDR_T_64BIT=y nova-core
> produces that following build failures:
>
>     error[E0308]: mismatched types
>       --> drivers/gpu/nova-core/fb.rs:49:59
>        |
>     49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle())?;
>        |                              -----------------------      ^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
>        |                              |
>        |                              arguments to this method are incorrect
>        |
>     note: method defined here
>       --> drivers/gpu/nova-core/fb/hal.rs:19:8
>        |
>     19 |     fn write_sysmem_flush_page(&self, bar: &Bar0, addr: u64) -> Result;
>        |        ^^^^^^^^^^^^^^^^^^^^^^^
>     help: you can convert a `u32` to a `u64`
>        |
>     49 |         hal::fb_hal(chipset).write_sysmem_flush_page(bar, page.dma_handle().into())?;
>        |                                                                            +++++++
>
>     error[E0308]: mismatched types
>       --> drivers/gpu/nova-core/fb.rs:65:47
>        |
>     65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle() {
>        |            -------------------------------    ^^^^^^^^^^^^^^^^^^^^^^ expected `u64`, found `u32`
>        |            |
>        |            expected because this is `u64`
>        |
>     help: you can convert a `u32` to a `u64`
>        |
>     65 |         if hal.read_sysmem_flush_page(bar) == self.page.dma_handle().into() {
>        |                                                                     +++++++
>
>     error: this arithmetic operation will overflow
>        --> drivers/gpu/nova-core/falcon.rs:469:23
>         |
>     469 |             .set_base((dma_start >> 40) as u16)
>         |                       ^^^^^^^^^^^^^^^^^ attempt to shift right by `40_i32`, which would overflow
>         |
>         = note: `#[deny(arithmetic_overflow)]` on by default
>
> This is due to the code making assumptions on the width of dma_addr_t to
> be 64 bit.
>
> While this could technically be handled, it is rather painful to deal
> with, as the following example illustrates:
>
> 	pub(super) fn read_sysmem_flush_page_ga100(bar: &Bar0) -> DmaAddress {
> 	    let addr = u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR::read(bar).adr_39_08())
> 	        << FLUSH_SYSMEM_ADDR_SHIFT
> 	        | u64::from(regs::NV_PFB_NISO_FLUSH_SYSMEM_ADDR_HI::read(bar).adr_63_40())
> 	            << FLUSH_SYSMEM_ADDR_SHIFT_HI;
>
> 	    addr.try_into().unwrap_or_else(|_| {
> 	        kernel::warn_on!(true);
>
> 	        0
> 	    })
> 	}
>
> At the same time there's not much value for nova-core to support 32-bit,
> given that the supported GPU architectures are Turing and later, hence
> depend on CONFIG_64BIT.
>
> Cc: John Hubbard <jhubbard@nvidia.com>
> Reported-by: Miguel Ojeda <ojeda@kernel.org>
> Closes: https://lore.kernel.org/lkml/20250828160247.37492-1-ojeda@kernel.org/
> Fixes: 6554ad65b589 ("gpu: nova-core: register sysmem flush page")
> Fixes: 69f5cd67ce41 ("gpu: nova-core: add falcon register definitions and base code")
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>

Applied to drm-rust-fixes, thanks!