On 21.08.2025 17:25, Teddy Astie wrote:
> @@ -686,10 +691,31 @@ static int domain_construct_memmap(libxl__gc *gc,
> /* We always own at least one lowmem entry. */
> unsigned int e820_entries = 1;
> struct e820entry *e820 = NULL;
> + uint64_t highmem_start = ((uint64_t)1 << 32);
> uint64_t highmem_size =
> dom->highmem_end ? dom->highmem_end - (1ull << 32) : 0;
> uint32_t lowmem_start = dom->device_model ? GUEST_LOW_MEM_START_DEFAULT
> : 0;
> unsigned page_size = XC_DOM_PAGE_SIZE(dom);
> + /* Special region starts at the first 1G boundary after the highmem */
> + uint64_t special_region_start =
> + (highmem_start + highmem_size + GB(1) - 1) & ~(GB(1) - 1);
That is, inaccessible before entering PAE mode?
The open-coding of ROUNDUP() also isn't nice, but sadly unavoidable as long
the the macro works in terms of unsigned long.
> @@ -769,6 +805,40 @@ static int domain_construct_memmap(libxl__gc *gc,
> e820[nr].type = E820_RAM;
> }
>
> + /* Special regions */
> + if (libxl_defbool_val(d_config->b_info.arch_x86.fixed_mem_layout))
> + {
> + e820[nr].type = XEN_HVM_MEMMAP_TYPE_SHARED_INFO;
> + e820[nr].addr = special_region_offset;
> + e820[nr].size = page_size;
> + special_region_offset += e820[nr].size;
> + nr++;
> +
> + if ( gnttab_frame_count )
> + {
> + e820[nr].type = XEN_HVM_MEMMAP_TYPE_GRANT_TABLE;
> + e820[nr].addr = special_region_offset;
> + e820[nr].size = gnttab_frame_count * page_size;
> + special_region_offset += e820[nr].size;
> + nr++;
> + }
> +
> + if (d_config->b_info.max_grant_version >= 2 &&
> gnttab_status_frame_count)
> + {
> + e820[nr].type = XEN_HVM_MEMMAP_TYPE_GNTTAB_STATUS;
> + e820[nr].addr = special_region_offset;
> + e820[nr].size = gnttab_status_frame_count * page_size;
> + special_region_offset += e820[nr].size;
> + nr++;
> + }
> +
> + e820[nr].type = XEN_HVM_MEMMAP_TYPE_FOREIGN_REG;
> + e820[nr].addr = special_region_offset;
> + e820[nr].size = MB(512);
Can we really know this is going to be enough for all use cases?
> --- a/xen/include/public/arch-x86/hvm/start_info.h
> +++ b/xen/include/public/arch-x86/hvm/start_info.h
> @@ -99,6 +99,13 @@
> #define XEN_HVM_MEMMAP_TYPE_DISABLED 6
> #define XEN_HVM_MEMMAP_TYPE_PMEM 7
>
> +/* Xen-specific types (OEM-specific range of the ACPI spec) */
> +#define XEN_HVM_MEMMAP_TYPE_SHARED_INFO 0xF0000001 /* Shared info page */
> +#define XEN_HVM_MEMMAP_TYPE_GRANT_TABLE 0xF0000002 /* Grant table pages */
> +#define XEN_HVM_MEMMAP_TYPE_GNTTAB_STATUS 0xF0000003 /* Grant table status
> page (v2) */
> +#define XEN_HVM_MEMMAP_TYPE_FOREIGN_REG 0xF0000004 /* Suitable region for
> grant mappings */
> + /* and foreign mappings
> */
I question it being legitimate for us to introduce new E820 types.
Jan
