Re: [PATCH 09/10] ACPI: IORT: Cast from ULL to phys_addr_t

From: Moritz Fischer <moritzf@google.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: David Airlie <airlied@gmail.com>,
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Subject: Re: [PATCH 09/10] ACPI: IORT: Cast from ULL to phys_addr_t
Date: Wed, 29 Nov 2023 06:18:25 +0000	[thread overview]
Message-ID: <20231129061825.altvhmgltws2bvhh@google.com> (raw)
In-Reply-To: <9-v1-720585788a7d+811b-iommu_fwspec_p1_jgg@nvidia.com>

On Tue, Nov 28, 2023 at 08:48:05PM -0400, Jason Gunthorpe wrote:
> gcc on i386 (when compile testing) warns:

This is a weird test. The Makefile for drivers/acpi/arm64 is conditional
on CONFIG_ARM64. How does this happen?

> 8->8
obj-$(CONFIG_ARM64)		+= arm64/
> 8->8

>   drivers/acpi/arm64/iort.c:2014:18: warning: implicit conversion  
> from 'unsigned long long' to 'phys_addr_t' (aka 'unsigned int') changes  
> value from 18446744073709551615 to 4294967295 [-Wconstant-conversion]
>                             local_limit =  
> DMA_BIT_MASK(ncomp->memory_address_limit);

> Because DMA_BIT_MASK returns a large ULL constant. Explicitly truncate it
> to phys_addr_t.

> Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> ---
>   drivers/acpi/arm64/iort.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)

> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
> index 6496ff5a6ba20d..bdaf9256870d92 100644
> --- a/drivers/acpi/arm64/iort.c
> +++ b/drivers/acpi/arm64/iort.c
> @@ -2011,7 +2011,8 @@ phys_addr_t __init  
> acpi_iort_dma_get_max_cpu_address(void)

>   		case ACPI_IORT_NODE_NAMED_COMPONENT:
>   			ncomp = (struct acpi_iort_named_component *)node->node_data;
> -			local_limit = DMA_BIT_MASK(ncomp->memory_address_limit);
> +			local_limit = (phys_addr_t)DMA_BIT_MASK(
> +				ncomp->memory_address_limit);
>   			limit = min_not_zero(limit, local_limit);
>   			break;

> @@ -2020,7 +2021,8 @@ phys_addr_t __init  
> acpi_iort_dma_get_max_cpu_address(void)
>   				break;

>   			rc = (struct acpi_iort_root_complex *)node->node_data;
> -			local_limit = DMA_BIT_MASK(rc->memory_address_limit);
> +			local_limit = (phys_addr_t)DMA_BIT_MASK(
> +				rc->memory_address_limit);
>   			limit = min_not_zero(limit, local_limit);
>   			break;
>   		}
> --
> 2.42.0

Cheers,
Moritz

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