On 10/9/24 11:13, Jan Beulich wrote:
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.
I think checking memmap_length is a better approach because as you say, the only time it will be zero is if no map was provided.
v/r, dps
