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

[Ayan Kumar Halder <ayankuma@xxxxxxx>]

Hi,

On 08/04/2025 10:54, Orzel, Michal wrote:
> On 07/04/2025 20:44, Ayan Kumar Halder wrote:
> > Add stubs to enable compilation
> NIT: missing dot at the end of sentence.
>
> > 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
> Sort alphabetically. Always.
>
> > 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 */
> > +
> > +#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 */
> > +
> > +#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
> At first sight, it's not clear why we diverge here and move Arm32 but not Arm64.
> At least I'd expect some reasoning for this change in commit msg.
I added an explaination why the code is moved for Arm32 in my latest patch.
> > +#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
> Why another #ifdef if there is one a few lines below in this file (below
> virt_to_maddr)?
Ack. I have moved it.
> > +#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
> Again, sort alphabetically.
>
> > 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 */
> empty line here
>
> > +#include <xen/domain_page.h>
> > +
> > +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:
> > + */
> Additionally, take into account Luca remarks regarding headers.
Thanks Luca for spotting them.

I have addressed all the other comments.

- Ayan

> ~Michal