The purpose of struct boot_module is to encapsulate the state of boot module as
it is processed by Xen. Locating boot module state struct boot_module reduces
the number of global variables as well as the number of state variables that
must be passed around. It also lays the groundwork for hyperlaunch mult-domain
construction, where multiple instances of state variables like headroom will be
needed.
Signed-off-by: Daniel P. Smith <dpsmith@apertussolutions.com>
Reviewed-by: Jason Andryuk <jason.andryuk@amd.com>
---
Changes since v7:
- adopted headroom comment from Andy Cooper
Changes since v6:
- add blank line to separate comment from line above it
Changes since v5:
- reword and expand comment on headroom
- consolidated declaration and assignment
---
xen/arch/x86/include/asm/bootinfo.h | 22 ++++++++++++++++++++++
xen/arch/x86/setup.c | 23 ++++++++---------------
2 files changed, 30 insertions(+), 15 deletions(-)
diff --git a/xen/arch/x86/include/asm/bootinfo.h b/xen/arch/x86/include/asm/bootinfo.h
index b1549d8c8f93..e337baa905f0 100644
--- a/xen/arch/x86/include/asm/bootinfo.h
+++ b/xen/arch/x86/include/asm/bootinfo.h
@@ -30,6 +30,28 @@ struct boot_module {
enum bootmod_type type;
+ /*
+ * A boot module may need decompressing by Xen. Headroom is an estimate of
+ * the additional space required to decompress the module.
+ *
+ * Headroom is accounted for at the start of the module. Decompressing is
+ * done in-place with input=start, output=start-headroom, expecting the
+ * pointers to become equal (give or take some rounding) when decompression
+ * is complete.
+ *
+ * Memory layout at boot:
+ *
+ * start ----+
+ * v
+ * |<-----headroom------>|<------size------->|
+ * +-------------------+
+ * | Compressed Module |
+ * +---------------------+-------------------+
+ * | Decompressed Module |
+ * +-----------------------------------------+
+ */
+ unsigned long headroom;
+
/*
* Module State Flags:
* relocated: indicates module has been relocated in memory.
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index e6d2d25fd038..633319d39d80 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -1062,7 +1062,7 @@ void asmlinkage __init noreturn __start_xen(void)
struct cpu_info *info = get_cpu_info(), *bsp_info;
unsigned int initrdidx, num_parked = 0;
struct boot_info *bi;
- unsigned long nr_pages, raw_max_page, modules_headroom;
+ unsigned long nr_pages, raw_max_page;
int i, j, e820_warn = 0, bytes = 0;
unsigned long eb_start, eb_end;
bool acpi_boot_table_init_done = false, relocated = false;
@@ -1443,7 +1443,7 @@ void asmlinkage __init noreturn __start_xen(void)
xen->mod->mod_end = __2M_rwdata_end - _stext;
}
- modules_headroom =
+ bi->mods[0].headroom =
bzimage_headroom(bootstrap_map_bm(&bi->mods[0]),
bi->mods[0].mod->mod_end);
bootstrap_unmap();
@@ -1526,14 +1526,7 @@ void asmlinkage __init noreturn __start_xen(void)
for ( j = bi->nr_modules - 1; j >= 0; j-- )
{
struct boot_module *bm = &bi->mods[j];
-
- /*
- * 'headroom' is a guess for the decompressed size and
- * decompressor overheads of mod[0] (the dom0 kernel). When we
- * move mod[0], we incorporate this as extra space at the start.
- */
- unsigned long headroom = j ? 0 : modules_headroom;
- unsigned long size = PAGE_ALIGN(headroom + bm->mod->mod_end);
+ unsigned long size = PAGE_ALIGN(bm->headroom + bm->mod->mod_end);
if ( bm->relocated )
continue;
@@ -1546,13 +1539,13 @@ void asmlinkage __init noreturn __start_xen(void)
continue;
if ( s < end &&
- (headroom ||
+ (bm->headroom ||
((end - size) >> PAGE_SHIFT) > bm->mod->mod_start) )
{
- move_memory(end - size + headroom,
+ move_memory(end - size + bm->headroom,
pfn_to_paddr(bm->mod->mod_start), bm->mod->mod_end);
bm->mod->mod_start = (end - size) >> PAGE_SHIFT;
- bm->mod->mod_end += headroom;
+ bm->mod->mod_end += bm->headroom;
bm->relocated = true;
}
}
@@ -1579,7 +1572,7 @@ void asmlinkage __init noreturn __start_xen(void)
#endif
}
- if ( modules_headroom && !bi->mods[0].relocated )
+ if ( bi->mods[0].headroom && !bi->mods[0].relocated )
panic("Not enough memory to relocate the dom0 kernel image\n");
for ( i = 0; i < bi->nr_modules; ++i )
{
@@ -2145,7 +2138,7 @@ void asmlinkage __init noreturn __start_xen(void)
* We're going to setup domain0 using the module(s) that we stashed safely
* above our heap. The second module, if present, is an initrd ramdisk.
*/
- dom0 = create_dom0(bi->mods[0].mod, modules_headroom,
+ dom0 = create_dom0(bi->mods[0].mod, bi->mods[0].headroom,
initrdidx < bi->nr_modules ? bi->mods[initrdidx].mod
: NULL,
kextra, bi->loader);
--
2.30.2On 02/11/2024 5:25 pm, Daniel P. Smith wrote:
> diff --git a/xen/arch/x86/include/asm/bootinfo.h b/xen/arch/x86/include/asm/bootinfo.h
> index b1549d8c8f93..e337baa905f0 100644
> --- a/xen/arch/x86/include/asm/bootinfo.h
> +++ b/xen/arch/x86/include/asm/bootinfo.h
> @@ -30,6 +30,28 @@ struct boot_module {
>
> enum bootmod_type type;
>
> + /*
> + * A boot module may need decompressing by Xen. Headroom is an estimate of
> + * the additional space required to decompress the module.
> + *
> + * Headroom is accounted for at the start of the module. Decompressing is
> + * done in-place with input=start, output=start-headroom, expecting the
> + * pointers to become equal (give or take some rounding) when decompression
> + * is complete.
> + *
> + * Memory layout at boot:
> + *
> + * start ----+
> + * v
> + * |<-----headroom------>|<------size------->|
> + * +-------------------+
> + * | Compressed Module |
> + * +---------------------+-------------------+
> + * | Decompressed Module |
> + * +-----------------------------------------+
> + */
> + unsigned long headroom;
> +
> /*
> * Module State Flags:
> * relocated: indicates module has been relocated in memory.
By the end of the series, this ends very poorly laid out.
It works a whole lot better when putting the bitfields between type and
headroom.
Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
On 11/6/24 18:00, Andrew Cooper wrote:
> On 02/11/2024 5:25 pm, Daniel P. Smith wrote:
>> diff --git a/xen/arch/x86/include/asm/bootinfo.h b/xen/arch/x86/include/asm/bootinfo.h
>> index b1549d8c8f93..e337baa905f0 100644
>> --- a/xen/arch/x86/include/asm/bootinfo.h
>> +++ b/xen/arch/x86/include/asm/bootinfo.h
>> @@ -30,6 +30,28 @@ struct boot_module {
>>
>> enum bootmod_type type;
>>
>> + /*
>> + * A boot module may need decompressing by Xen. Headroom is an estimate of
>> + * the additional space required to decompress the module.
>> + *
>> + * Headroom is accounted for at the start of the module. Decompressing is
>> + * done in-place with input=start, output=start-headroom, expecting the
>> + * pointers to become equal (give or take some rounding) when decompression
>> + * is complete.
>> + *
>> + * Memory layout at boot:
>> + *
>> + * start ----+
>> + * v
>> + * |<-----headroom------>|<------size------->|
>> + * +-------------------+
>> + * | Compressed Module |
>> + * +---------------------+-------------------+
>> + * | Decompressed Module |
>> + * +-----------------------------------------+
>> + */
>> + unsigned long headroom;
>> +
>> /*
>> * Module State Flags:
>> * relocated: indicates module has been relocated in memory.
>
> By the end of the series, this ends very poorly laid out.
>
> It works a whole lot better when putting the bitfields between type and
> headroom.
Ack.
> Otherwise, Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
Thanks.
v/r,
dps
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