Re: [PATCH 02/16] acpi: vmap pages in acpi_os_alloc_memory

[Julien Grall <julien.grall.oss@xxxxxxxxx>]

Hi,

On Thu, 30 Apr 2020 at 21:44, Hongyan Xia <hx242@xxxxxxx> wrote:
>
> From: Hongyan Xia <hongyxia@xxxxxxxxxx>
>
> Also, introduce a wrapper around vmap that maps a contiguous range for
> boot allocations.
>
> Signed-off-by: Hongyan Xia <hongyxia@xxxxxxxxxx>
> ---
>  xen/drivers/acpi/osl.c | 9 ++++++++-
>  xen/include/xen/vmap.h | 5 +++++
>  2 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/xen/drivers/acpi/osl.c b/xen/drivers/acpi/osl.c
> index 4c8bb7839e..d0762dad4e 100644
> --- a/xen/drivers/acpi/osl.c
> +++ b/xen/drivers/acpi/osl.c
> @@ -219,7 +219,11 @@ void *__init acpi_os_alloc_memory(size_t sz)
>         void *ptr;
>
>         if (system_state == SYS_STATE_early_boot)
> -               return mfn_to_virt(mfn_x(alloc_boot_pages(PFN_UP(sz), 1)));
> +       {
> +               mfn_t mfn = alloc_boot_pages(PFN_UP(sz), 1);
> +
> +               return vmap_boot_pages(mfn, PFN_UP(sz));
> +       }
>
>         ptr = xmalloc_bytes(sz);
>         ASSERT(!ptr || is_xmalloc_memory(ptr));
> @@ -244,5 +248,8 @@ void __init acpi_os_free_memory(void *ptr)
>         if (is_xmalloc_memory(ptr))
>                 xfree(ptr);
>         else if (ptr && system_state == SYS_STATE_early_boot)
> +       {
> +               vunmap(ptr);
>                 init_boot_pages(__pa(ptr), __pa(ptr) + PAGE_SIZE);

__pa(ptr) can only work on the direct map. Even worth, on Arm it will
fault because there is no mapping.
I think you will want to use vmap_to_mfn() before calling vunmap().

Cheers,