Hi Carlo,
On 03/12/2024 11:37, Carlo Nonato wrote:
On Tue, Dec 3, 2024 at 11:36 AM Julien Grall <jul...@xen.org> wrote:
On 03/12/2024 10:08, Carlo Nonato wrote:
Hi Julien,
On Mon, Dec 2, 2024 at 10:44 PM Julien Grall <jul...@xen.org> wrote:
Hi Carlo,
[...]
diff --git a/xen/arch/arm/arm64/mmu/mm.c b/xen/arch/arm/arm64/mmu/mm.c
index 671eaadbc1..3732d5897e 100644
--- a/xen/arch/arm/arm64/mmu/mm.c
+++ b/xen/arch/arm/arm64/mmu/mm.c
@@ -1,6 +1,7 @@
/* SPDX-License-Identifier: GPL-2.0-only */
#include <xen/init.h>
+#include <xen/llc-coloring.h>
#include <xen/mm.h>
#include <xen/pfn.h>
@@ -138,27 +139,46 @@ void update_boot_mapping(bool enable)
}
extern void switch_ttbr_id(uint64_t ttbr);
+extern void relocate_xen(uint64_t ttbr, void *src, void *dst, size_t len);
typedef void (switch_ttbr_fn)(uint64_t ttbr);
+typedef void (relocate_xen_fn)(uint64_t ttbr, void *src, void *dst, size_t
len);
void __init switch_ttbr(uint64_t ttbr)
Given the change below, I think this function needs to be renamed.
Possibly to relocate_and_jump() with a comment explaning that the
relocation only happen for cache-coloring.
Changing the name of switch_ttbr() to relocate_and_jump() seems a bit
misleading to me. First I need to change the name also for arm32 where there's
no relocation at all. Second, relocation is something that happens
conditionally so I don't think it's a good name for the function.
Feel free to propose a new name. The main thing is the current name
can't stay "switch_ttbr()" because you are doing more than switching the
TTBR.
The other solution is to have a separate call for relocating xen (which
will fall-through to switch_ttbr) and another one for those that only to
switch TTBR.
What about a function like this one, defined in xen/arch/arm/arm64/mmu/mm.c:
typedef void (relocate_xen_fn)(uint64_t ttbr, void *src, void *dst, size_t len);
void __init relocate_and_switch_ttbr(uint64_t ttbr) {
vaddr_t id_addr = virt_to_maddr(relocate_xen);
relocate_xen_fn *fn = (relocate_xen_fn *)id_addr;
lpae_t pte;
/* Enable the identity mapping in the boot page tables */
update_identity_mapping(true);
/* Enable the identity mapping in the runtime page tables */
pte = pte_of_xenaddr((vaddr_t)relocate_xen);
pte.pt.table = 1;
pte.pt.xn = 0;
pte.pt.ro = 1;
write_pte(&xen_third_id[third_table_offset(id_addr)], pte);
/* Relocate Xen and switch TTBR */
fn(ttbr, _start, (void *)BOOT_RELOC_VIRT_START, _end - _start);
/*
* Disable the identity mapping in the runtime page tables.
* Note it is not necessary to disable it in the boot page tables
* because they are not going to be used by this CPU anymore.
*/
update_identity_mapping(false);
}
which is actually a clone of switch_ttbr() but it does relocation. I would
then call it in case of coloring in setup_pagetables(). This should go in the
direction you suggested, but it would duplicate a bit of code. What do you
think about it?
I think the duplication is fine here.
It would be possible to reduce the duplication is we introduce an helper
for call update_identity_mapping(true) and update the PTE. But I am not
sure it is worth it.
Cheers,
--
Julien Grall
