[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [XEN v3 6/9] xen/arm: Introduce choice to enable 64/32 bit physical addressing
Hi Ayan, On 08/02/2023 12:05, Ayan Kumar Halder wrote: So you likely don't want to allow the user to select them directly (IOW remove the help section). However, I don't see any code using it. Did you actually intended to use PHYS_ADDR_{32, 64} in the code?Some Arm based hardware platforms which does not support LPAE (eg Cortex-R52), uses 32 bit physical addresses. Also, users may choose to use 32 bits to represent physical addresses for optimization. To support the above use cases, we have introduced arch independent configs to choose if the physical address can be represented using 32 bits (PHYS_ADDR_32) or 64 bits (PHYS_ADDR_64). For now only ARM_32 provides support to enable 32 bit physical addressing. Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx> --- Changes from - v1 - 1. Extracted from "[XEN v1 8/9] xen/arm: Other adaptations required to support 32bit paddr". v2 - 1. Introduced Kconfig choice. ARM_64 can select PHYS_ADDR_64 only whereas ARM_32 can select PHYS_ADDR_32 or PHYS_ADDR_64. 2. For CONFIG_ARM_PA_32, paddr_t is defined as 'unsigned long'. (Jan,Julien please let me know if I understood your suggestion about Kconfig correctly). xen/arch/Kconfig | 12 +++++++++++ xen/arch/arm/Kconfig | 31 ++++++++++++++++++++++++++++ xen/arch/arm/include/asm/page-bits.h | 2 ++ xen/arch/arm/include/asm/types.h | 6 ++++++ 4 files changed, 51 insertions(+) diff --git a/xen/arch/Kconfig b/xen/arch/Kconfig index 7028f7b74f..1eff312b51 100644 --- a/xen/arch/Kconfig +++ b/xen/arch/Kconfig @@ -1,6 +1,18 @@ config 64BIT bool+config PHYS_ADDR_32+ bool + help + Select this option if the physical addresses can be represented by + 32 bits. + +config PHYS_ADDR_64 + bool + help + Select this option if the physical addresses can be represented + 64 bits. + config NR_CPUS int "Maximum number of CPUs" range 1 4095 diff --git a/xen/arch/arm/Kconfig b/xen/arch/arm/Kconfig index 239d3aed3c..0955891e86 100644 --- a/xen/arch/arm/Kconfig +++ b/xen/arch/arm/Kconfig @@ -18,6 +18,37 @@ config ARM select HAS_PDX select HAS_PMAP select IOMMU_FORCE_PT_SHARE + choice I think this is a bit odd that this choice is part of CONFIG_ARM. It would be better it is separate. You can do that by removing one indentation. + bool "Representative width for any physical address (default 64bit)" + optional + ---help--- + You may want to specify the width to represent the physical + address space. + By default, the physical addresses are represented using + 64 bits. + + However in certain platforms, the physical addresses may be + represented using 32 bits. + Also, the user may decide that the physical addresses can be + represented using 32 bits for a given SoC. In those cases, + user may want to enable 32 bit physical address for + optimization. + For now, we have enabled this choice for ARM_32 only. + + config ARM_PA_64 + select PHYS_ADDR_64 + bool "Select 64 bits to represent physical address" + ---help--- + Use 64 bits to represent physical address. + + config ARM_PA_32 + select PHYS_ADDR_32 + depends on ARM_32 + bool "Select 32 bits to represent physical address" + ---help--- + Use 32 bits to represent physical address. As I wrote in v2, I think this is a bit odd to ask the user what would be the width of paddr_t. It is also not scalable if we decide in the future to define different PADDR_BITS (i.e. 48, 40, 36, 32). So it would be better to allow the user to define PADDR_BITS that can then be translated by Xen to which ever paddr_t is suitable. Something like: choice prompt: "Physical address space size" if ARM_32 default ARM_PA_48 if ARM_64 default AMR_PA_40 if ARM_32 help ... config ARM_PA_BITS_32 bool "32-bit" help XXX Add help here to explain the benefits of using 32-bit. select PHYS_ADDR_T_32 depends on ARM_32 config ARM_PA_BITS_40 bool "40-bit" select PHYS_ADDR_T_64 depends on ARM_32 config ARM_PA_BITS_48 bool "40-bit" select PHYS_ADDR_T_64 depends on ARM_48 endchoice config PADDR_BITS int default 32 if ARM_PA_BITS_32 default 40 if ARM_PA_BITS_40 default 48 if ARM_PA_BITS_48With this approach, there would be no structural change in the Kconfig if we wanted to support 32/40-bit on Arm64. + + endchoiceconfig ARCH_DEFCONFIGstring diff --git a/xen/arch/arm/include/asm/page-bits.h b/xen/arch/arm/include/asm/page-bits.h index 5d6477e599..8f4dcebcfd 100644 --- a/xen/arch/arm/include/asm/page-bits.h +++ b/xen/arch/arm/include/asm/page-bits.h @@ -5,6 +5,8 @@#ifdef CONFIG_ARM_64#define PADDR_BITS 48 +#elif CONFIG_ARM_PA_32 +#define PADDR_BITS 32 #else #define PADDR_BITS 40 #endif With what I suggested above. This would be replaced with: #define PADDR_BITS CONFIG_PADDR_BITS diff --git a/xen/arch/arm/include/asm/types.h b/xen/arch/arm/include/asm/types.h index e218ed77bd..26144bc87e 100644 --- a/xen/arch/arm/include/asm/types.h +++ b/xen/arch/arm/include/asm/types.h @@ -34,9 +34,15 @@ typedef signed long long s64; typedef unsigned long long u64; typedef u32 vaddr_t; #define PRIvaddr PRIx32 +#if defined(CONFIG_ARM_PA_32) And this could be replaced with #ifdef CONFIG_PHY_ADDR_T_32 I would also consider to add the following in mm.c BUILD_BUG_ON((sizeof(paddr_t) * 8) < PADDR_BITS); This is to make sure that the PADDR_BITS will always fit in paddr_t. +typedef unsigned long paddr_t; +#define INVALID_PADDR (~0UL) +#define PRIpaddr "08lx" +#else typedef u64 paddr_t; #define INVALID_PADDR (~0ULL) #define PRIpaddr "016llx" +#endif typedef u32 register_t; #define PRIregister "08x" #elif defined (CONFIG_ARM_64) Cheers, -- Julien Grall
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