Re: [PATCH 4/4] xen/arm: Introduce fw_unreserved_regions() and use it

From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien@xen.org>
Cc: xen-devel@lists.xenproject.org, alex.bennee@linaro.org,
	 masami.hiramatsu@linaro.org, ehem+xen@m5p.com,
	bertrand.marquis@arm.com,  andre.przywara@arm.com,
	Julien Grall <jgrall@amazon.com>,
	 Stefano Stabellini <sstabellini@kernel.org>,
	 Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [PATCH 4/4] xen/arm: Introduce fw_unreserved_regions() and use it
Date: Wed, 30 Sep 2020 16:40:51 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.2009301630250.10908@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <20200926205542.9261-5-julien@xen.org>

On Sat, 26 Sep 2020, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> Since commit 6e3e77120378 "xen/arm: setup: Relocate the Device-Tree
> later on in the boot", the device-tree will not be kept mapped when
> using ACPI.
> 
> However, a few places are calling dt_unreserved_regions() which expects
> a valid DT. This will lead to a crash.
> 
> As the DT should not be used for ACPI (other than for detecting the
> modules), a new function fw_unreserved_regions() is introduced.
> 
> It will behave the same way on DT system. On ACPI system, it will
> unreserve the whole region.

The patch is good.

Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>

I have a small suggestion for improvement that could be done on commit:
given that bootinfo is actually used on EFI systems (granted, not
bootinfo.reserved_mem but bootinfo.mem, see
xen/arch/arm/efi/efi-boot.h:efi_process_memory_map_bootinfo) so
technically bootinfo could be in-use with ACPI, maybe we could add a
comment on top of xen/include/asm-arm/setup.h:bootinfo to say that
reserved_mem is device tree only?

> Signed-off-by: Julien Grall <jgrall@amazon.com>
> 
> ---
> 
> Is there any region we should exclude on ACPI?
> ---
>  xen/arch/arm/kernel.c       |  2 +-
>  xen/arch/arm/setup.c        | 22 +++++++++++++++++-----
>  xen/include/asm-arm/setup.h |  2 +-
>  3 files changed, 19 insertions(+), 7 deletions(-)
> 
> diff --git a/xen/arch/arm/kernel.c b/xen/arch/arm/kernel.c
> index 032923853f2c..ab78689ed2a6 100644
> --- a/xen/arch/arm/kernel.c
> +++ b/xen/arch/arm/kernel.c
> @@ -307,7 +307,7 @@ static __init int kernel_decompress(struct bootmodule *mod)
>       * Free the original kernel, update the pointers to the
>       * decompressed kernel
>       */
> -    dt_unreserved_regions(addr, addr + size, init_domheap_pages, 0);
> +    fw_unreserved_regions(addr, addr + size, init_domheap_pages, 0);
>  
>      return 0;
>  }
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 35e5bee04efa..7fcff9af2a7e 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -196,8 +196,9 @@ static void __init processor_id(void)
>      processor_setup();
>  }
>  
> -void __init dt_unreserved_regions(paddr_t s, paddr_t e,
> -                                  void (*cb)(paddr_t, paddr_t), int first)
> +static void __init dt_unreserved_regions(paddr_t s, paddr_t e,
> +                                         void (*cb)(paddr_t, paddr_t),
> +                                         int first)
>  {
>      int i, nr = fdt_num_mem_rsv(device_tree_flattened);
>  
> @@ -244,6 +245,17 @@ void __init dt_unreserved_regions(paddr_t s, paddr_t e,
>      cb(s, e);
>  }
>  
> +void __init fw_unreserved_regions(paddr_t s, paddr_t e,
> +                                  void (*cb)(paddr_t, paddr_t), int first)
> +{
> +    if ( acpi_disabled )
> +        dt_unreserved_regions(s, e, cb, first);
> +    else
> +        cb(s, e);
> +}
> +
> +
> +
>  struct bootmodule __init *add_boot_module(bootmodule_kind kind,
>                                            paddr_t start, paddr_t size,
>                                            bool domU)
> @@ -405,7 +417,7 @@ void __init discard_initial_modules(void)
>               !mfn_valid(maddr_to_mfn(e)) )
>              continue;
>  
> -        dt_unreserved_regions(s, e, init_domheap_pages, 0);
> +        fw_unreserved_regions(s, e, init_domheap_pages, 0);
>      }
>  
>      mi->nr_mods = 0;
> @@ -712,7 +724,7 @@ static void __init setup_mm(void)
>                  n = mfn_to_maddr(mfn_add(xenheap_mfn_start, xenheap_pages));
>              }
>  
> -            dt_unreserved_regions(s, e, init_boot_pages, 0);
> +            fw_unreserved_regions(s, e, init_boot_pages, 0);
>  
>              s = n;
>          }
> @@ -765,7 +777,7 @@ static void __init setup_mm(void)
>              if ( e > bank_end )
>                  e = bank_end;
>  
> -            dt_unreserved_regions(s, e, init_boot_pages, 0);
> +            fw_unreserved_regions(s, e, init_boot_pages, 0);
>              s = n;
>          }
>      }
> diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
> index 2f8f24e286ed..34df23247b87 100644
> --- a/xen/include/asm-arm/setup.h
> +++ b/xen/include/asm-arm/setup.h
> @@ -96,7 +96,7 @@ int construct_dom0(struct domain *d);
>  void create_domUs(void);
>  
>  void discard_initial_modules(void);
> -void dt_unreserved_regions(paddr_t s, paddr_t e,
> +void fw_unreserved_regions(paddr_t s, paddr_t e,
>                             void (*cb)(paddr_t, paddr_t), int first);
>  
>  size_t boot_fdt_info(const void *fdt, paddr_t paddr);
> -- 
> 2.17.1
> 