Mailing List Archive

commit 68b2672a63280fa180f4e52c5dab54b04b1369ad
Author: Andrew Cooper <andrew.cooper3@citrix.com>
AuthorDate: Mon Dec 6 19:16:23 2021 +0000
Commit: Andrew Cooper <andrew.cooper3@citrix.com>
CommitDate: Mon Dec 19 11:01:46 2022 +0000

x86/boot: Relocate Xen using memcpy() directly

We can relocate Xen by reading out of the virtual mapping that we're executing
on, and write directly into the directmap. In fact, this removes one
dependency on Xen being "at 0" (the XEN_IMG_OFFSET passed as src) for
relocation to occur.

This removes all the temporary pagetable handling under the covers of
move_memory(), and results in a forward copy rather than a chunked backwards
copy (caused by move_memory() always constructing src and dst in a way to
trigger memmove() to copy backwards).

With the penultimate caller of move_memory() dropped, clean up the API. Drop
the keep boolean, folding in 0 from the final caller, and drop the return
address which has been unused since c/s 0b76ce20de85 ("x86/setup: don't
relocate the VGA hole.") in 2007.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
xen/arch/x86/setup.c | 15 ++++-----------
1 file changed, 4 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 6bb5bc7c84..4102aae76d 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -425,8 +425,8 @@ void *__init bootstrap_map(const module_t *mod)
return ret;
}

-static void *__init move_memory(
- uint64_t dst, uint64_t src, unsigned int size, bool keep)
+static void __init move_memory(
+ uint64_t dst, uint64_t src, unsigned int size)
{
unsigned int blksz = BOOTSTRAP_MAP_LIMIT - BOOTSTRAP_MAP_BASE;
unsigned int mask = (1L << L2_PAGETABLE_SHIFT) - 1;
@@ -463,13 +463,8 @@ static void *__init move_memory(
src += sz;
size -= sz;

- if ( keep )
- return size ? NULL : d + doffs;
-
bootstrap_map(NULL);
}
-
- return NULL;
}

#undef BOOTSTRAP_MAP_LIMIT
@@ -1277,7 +1272,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
* data until after we have switched to the relocated pagetables!
*/
barrier();
- move_memory(e, XEN_IMG_OFFSET, _end - _start, 1);
+ memcpy(__va(__pa(_start)), _start, _end - _start);

/* Walk idle_pg_table, relocating non-leaf entries. */
pl4e = __va(__pa(idle_pg_table));
@@ -1334,8 +1329,6 @@ void __init noreturn __start_xen(unsigned long mbi_p)
"1" (__va(__pa(cpu0_stack))), "2" (STACK_SIZE / 8)
: "memory" );

- bootstrap_map(NULL);
-
printk("New Xen image base address: %#lx\n", xen_phys_start);
}

@@ -1361,7 +1354,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
{
move_memory(end - size + headroom,
(uint64_t)mod[j].mod_start << PAGE_SHIFT,
- mod[j].mod_end, 0);
+ mod[j].mod_end);
mod[j].mod_start = (end - size) >> PAGE_SHIFT;
mod[j].mod_end += headroom;
mod[j].reserved = 1;
--
generated by git-patchbot for /home/xen/git/xen.git#master