Re: [PATCH v3 18/20] xen/riscv: implement mfn_valid() and page reference, ownership handling helpers

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 8/11/25 2:50 PM, Jan Beulich wrote:

> On 31.07.2025 17:58, Oleksii Kurochko wrote:
> > Implement the mfn_valid() macro to verify whether a given MFN is valid by
> > checking that it falls within the range [start_page, max_page).
> > These bounds are initialized based on the start and end addresses of RAM.
> >
> > As part of this patch, start_page is introduced and initialized with the
> > PFN of the first RAM page.
> > Also, initialize pdx_group_valid() by calling set_pdx_range() when
> > memory banks are being mapped.
> >
> > Also, after providing a non-stub implementation of the mfn_valid() macro,
> > the following compilation errors started to occur:
> >   riscv64-linux-gnu-ld: prelink.o: in function `__next_node':
> >   /build/xen/./include/xen/nodemask.h:202: undefined reference to `page_is_ram_type'
> >   riscv64-linux-gnu-ld: prelink.o: in function `get_free_buddy':
> >   /build/xen/common/page_alloc.c:881: undefined reference to `page_is_ram_type'
> >   riscv64-linux-gnu-ld: prelink.o: in function `alloc_heap_pages':
> >   /build/xen/common/page_alloc.c:1043: undefined reference to `page_get_owner_and_reference'
> >   riscv64-linux-gnu-ld: /build/xen/common/page_alloc.c:1098: undefined reference to `page_is_ram_type'
> >   riscv64-linux-gnu-ld: prelink.o: in function `ns16550_interrupt':
> >   /build/xen/drivers/char/ns16550.c:205: undefined reference to `get_page'
> >   riscv64-linux-gnu-ld: ./.xen-syms.0: hidden symbol `page_get_owner_and_reference' isn't defined
> >   riscv64-linux-gnu-ld: final link failed: bad value
> >   make[2]: *** [arch/riscv/Makefile:35: xen-syms] Error 1
> > To resolve these errors, the following functions have also been introduced,
> > based on their Arm counterparts:
> > - page_get_owner_and_reference() and its variant to safely acquire a
> >   reference to a page and retrieve its owner.
> > - A stub for page_is_ram_type() that currently always returns 0 and asserts
> >   unreachable, as RAM type checking is not yet implemented.
> >       
> For this latter part I can only repeat that the code is reachable, and hence it
> is wrong to put ASSERT_UNREACHABLE() there. That's true for Arm's code as well.
>     
I will drop this stuff in the next patch version.
> > Signed-off-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
> >       
> With said line dropped:
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>     
Thanks.

~ Oleksii