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Re: [PATCH v5 04/44] x86/boot: move mmap info to boot info
- To: "Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Wed, 9 Oct 2024 17:13:17 +0200
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- Cc: jason.andryuk@xxxxxxx, christopher.w.clark@xxxxxxxxx, stefano.stabellini@xxxxxxx, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Wed, 09 Oct 2024 15:13:38 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 06.10.2024 23:49, Daniel P. Smith wrote:
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -296,6 +296,12 @@ static struct boot_info __init
> *multiboot_fill_boot_info(unsigned long mbi_p)
> else
> bi->cmdline = "";
>
> + if ( mbi->flags & MBI_MEMMAP )
> + {
> + bi->memmap_addr = mbi->mmap_addr;
> + bi->memmap_length = mbi->mmap_length;
> + }
> +
> return bi;
> }
>
> @@ -1185,13 +1191,13 @@ void asmlinkage __init noreturn __start_xen(unsigned
> long mbi_p)
> {
> memmap_type = "Xen-e820";
> }
> - else if ( mbi->flags & MBI_MEMMAP )
> + else if ( bi->memmap_addr )
I'd like to note that this isn't an exact transformation, as with the flag
set the memory map could theoretically also like at address 0. As long as
the legacy BIOS layout of low memory is as it is, that won't happen. I'm
less certain going forward, for legacy-free hardware/firmware. Imo at the
very least this needs mentioning as intentional in the description, for
archeologists to later be able to tell whether this was an oversight.
Or maybe it would be better to check ->memmap_length? That being zero
clearly means there's effectively no map.
Jan
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