Re: [PATCH v5 3/3] xen/arm32: mpu: Stubs to build MPU for arm32

[Luca Fancellu <Luca.Fancellu@xxxxxxx>]

Hi Ayan,

> On 7 Apr 2025, at 19:44, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx> wrote:
> 
> Add stubs to enable compilation
> 
> Signed-off-by: Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>
> ---
> Changes from :-
> 
> v1, v2 -
> 1. New patch introduced in v3.
> 2. Should be applied on top of
> https://patchwork.kernel.org/project/xen-devel/cover/20250316192445.2376484-1-luca.fancellu@xxxxxxx/
> 
> v3 -
> 1. Add stubs for map_domain_page() and similar functions.
> 
> 2. 'BUG_ON("unimplemented")' is kept in all the stubs.
> 
> v4 - 
> 1. is_xen_heap_mfn() macros are defined across mpu/mm.h (ARM32 specific)
> , mmu/mm.h (ARM32 specific) and asm/mm.h (ARM64 specific)
> 
> 2. s/(void*)0/NULL
> 
> xen/arch/arm/arm32/mpu/Makefile   |  2 ++
> xen/arch/arm/arm32/mpu/p2m.c      | 18 ++++++++++++++
> xen/arch/arm/arm32/mpu/smpboot.c  | 23 +++++++++++++++++
> xen/arch/arm/include/asm/mm.h     |  9 +------
> xen/arch/arm/include/asm/mmu/mm.h |  9 +++++++
> xen/arch/arm/include/asm/mpu/mm.h |  5 ++++
> xen/arch/arm/mpu/Makefile         |  1 +
> xen/arch/arm/mpu/domain_page.c    | 41 +++++++++++++++++++++++++++++++
> 8 files changed, 100 insertions(+), 8 deletions(-)
> create mode 100644 xen/arch/arm/arm32/mpu/p2m.c
> create mode 100644 xen/arch/arm/arm32/mpu/smpboot.c
> create mode 100644 xen/arch/arm/mpu/domain_page.c
> 
> diff --git a/xen/arch/arm/arm32/mpu/Makefile b/xen/arch/arm/arm32/mpu/Makefile
> index 3340058c08..38797f28af 100644
> --- a/xen/arch/arm/arm32/mpu/Makefile
> +++ b/xen/arch/arm/arm32/mpu/Makefile
> @@ -1 +1,3 @@
> obj-y += head.o
> +obj-y += smpboot.o
> +obj-y += p2m.o
> diff --git a/xen/arch/arm/arm32/mpu/p2m.c b/xen/arch/arm/arm32/mpu/p2m.c
> new file mode 100644
> index 0000000000..df8de5c7d8
> --- /dev/null
> +++ b/xen/arch/arm/arm32/mpu/p2m.c
> @@ -0,0 +1,18 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +

I would add:
#include <xen/bug.h>
for BUG()

> +#include <xen/init.h>
> +#include <asm/p2m.h>
> +
> +void __init setup_virt_paging(void)
> +{
> +    BUG_ON("unimplemented");
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/arm32/mpu/smpboot.c 
> b/xen/arch/arm/arm32/mpu/smpboot.c
> new file mode 100644
> index 0000000000..3f3e54294e
> --- /dev/null
> +++ b/xen/arch/arm/arm32/mpu/smpboot.c
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +

I would add:
#include <xen/bug.h>
for BUG()

#include <xen/errno.h>
for EINVAL

#include <xen/stdbool.h>
for bool

> +#include <xen/mm.h>
> +
> +int prepare_secondary_mm(int cpu)
> +{
> +    BUG_ON("unimplemented");
> +    return -EINVAL;
> +}
> +
> +void update_boot_mapping(bool enable)
> +{
> +    BUG_ON("unimplemented");
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
> index fbffaccef4..5b67c0f8bb 100644
> --- a/xen/arch/arm/include/asm/mm.h
> +++ b/xen/arch/arm/include/asm/mm.h
> @@ -170,14 +170,7 @@ struct page_info
> #define _PGC_need_scrub   _PGC_allocated
> #define PGC_need_scrub    PGC_allocated
> 
> -#ifdef CONFIG_ARM_32
> -#define is_xen_heap_page(page) is_xen_heap_mfn(page_to_mfn(page))
> -#define is_xen_heap_mfn(mfn) ({                                 \
> -    unsigned long mfn_ = mfn_x(mfn);                            \
> -    (mfn_ >= mfn_x(directmap_mfn_start) &&                      \
> -     mfn_ < mfn_x(directmap_mfn_end));                          \
> -})
> -#else
> +#ifdef CONFIG_ARM_64
> #define is_xen_heap_page(page) ((page)->count_info & PGC_xen_heap)
> #define is_xen_heap_mfn(mfn) \
>     (mfn_valid(mfn) && is_xen_heap_page(mfn_to_page(mfn)))
> diff --git a/xen/arch/arm/include/asm/mmu/mm.h 
> b/xen/arch/arm/include/asm/mmu/mm.h
> index caba987edc..9b98d12b07 100644
> --- a/xen/arch/arm/include/asm/mmu/mm.h
> +++ b/xen/arch/arm/include/asm/mmu/mm.h
> @@ -21,6 +21,15 @@ extern unsigned long directmap_base_pdx;
> 
> #define frame_table ((struct page_info *)FRAMETABLE_VIRT_START)
> 
> +#ifdef CONFIG_ARM_32
> +#define is_xen_heap_page(page) is_xen_heap_mfn(page_to_mfn(page))
> +#define is_xen_heap_mfn(mfn) ({                                 \
> +    unsigned long mfn_ = mfn_x(mfn);                            \
> +    (mfn_ >= mfn_x(directmap_mfn_start) &&                      \
> +     mfn_ < mfn_x(directmap_mfn_end));                          \
> +})
> +#endif
> +
> #define virt_to_maddr(va) ({                                                  
>  \
>     vaddr_t va_ = (vaddr_t)(va);                                              
>  \
>     (paddr_t)((va_to_par(va_) & PADDR_MASK & PAGE_MASK) | (va_ & 
> ~PAGE_MASK)); \
> diff --git a/xen/arch/arm/include/asm/mpu/mm.h 
> b/xen/arch/arm/include/asm/mpu/mm.h
> index 86f33d9836..bfd840fa5d 100644
> --- a/xen/arch/arm/include/asm/mpu/mm.h
> +++ b/xen/arch/arm/include/asm/mpu/mm.h
> @@ -13,6 +13,11 @@ extern struct page_info *frame_table;
> 
> #define virt_to_maddr(va) ((paddr_t)((vaddr_t)(va) & PADDR_MASK))
> 
> +#ifdef CONFIG_ARM_32
> +#define is_xen_heap_page(page) ({ BUG_ON("unimplemented"); false; })
> +#define is_xen_heap_mfn(mfn) ({ BUG_ON("unimplemented"); false; })
> +#endif
> +
> /* On MPU systems there is no translation, ma == va. */
> static inline void *maddr_to_virt(paddr_t ma)
> {
> diff --git a/xen/arch/arm/mpu/Makefile b/xen/arch/arm/mpu/Makefile
> index 21bbc517b5..ff221011d5 100644
> --- a/xen/arch/arm/mpu/Makefile
> +++ b/xen/arch/arm/mpu/Makefile
> @@ -2,3 +2,4 @@ obj-y += mm.o
> obj-y += p2m.o
> obj-y += setup.init.o
> obj-y += vmap.o
> +obj-$(CONFIG_ARM_32) += domain_page.o
> diff --git a/xen/arch/arm/mpu/domain_page.c b/xen/arch/arm/mpu/domain_page.c
> new file mode 100644
> index 0000000000..8859b24e04
> --- /dev/null
> +++ b/xen/arch/arm/mpu/domain_page.c
> @@ -0,0 +1,41 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +#include <xen/domain_page.h>

I would add:

#include <xen/bug.h>
for BUG()

#include <xen/mm-frame.h>
for mfn_t and INVALID_MFN

#include <xen/types.h>
for NULL


> +
> +void *map_domain_page_global(mfn_t mfn)
> +{
> +    BUG_ON("unimplemented");
> +    return NULL;
> +}
> +
> +/* Map a page of domheap memory */
> +void *map_domain_page(mfn_t mfn)
> +{
> +    BUG_ON("unimplemented");
> +    return NULL;
> +}
> +
> +/* Release a mapping taken with map_domain_page() */
> +void unmap_domain_page(const void *ptr)
> +{
> +    BUG_ON("unimplemented");
> +}
> +
> +mfn_t domain_page_map_to_mfn(const void *ptr)
> +{
> +    BUG_ON("unimplemented");
> +    return INVALID_MFN;
> +}
> +
> +void unmap_domain_page_global(const void *va)
> +{
> +    BUG_ON("unimplemented");
> +}
> +
> +/*
> + * Local variables:
> + * mode: C
> + * c-file-style: "BSD"
> + * c-basic-offset: 4
> + * indent-tabs-mode: nil
> + * End:
> + */
> -- 
> 2.25.1

with the above addressed, at least for me it looks good!

Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>

Cheers,
Luca