On 17/01/2024 08:30, Michal Orzel wrote:
Hi Julien,
Hi Michal,
On 16/01/2024 15:37, Julien Grall wrote:
From: Julien Grall <[email protected]>
With the upcoming work to color Xen, the binary will not be anymore
physically contiguous. This will be a problem during boot as the
assembly code will need to work out where each piece of Xen reside.
An easy way to solve the issue is to have all code/data accessed
by the secondary CPUs while the MMU is off within a single page.
Right now, init_ttbr is used by secondary CPUs to find there page-tables
before the MMU is on. Yet it is currently in .data which is unlikely
to be within the same page as the rest of the idmap.
Create a new section .data.idmap that will be used for variables
accessed by the early boot code. The first one is init_ttbr.
The idmap is currently part of the text section and therefore will
be mapped read-only executable. This means that we need to temporarily
remap init_ttbr in order to update it.
Introduce a new function set_init_ttbr() for this purpose so the code
is not duplicated between arm64 and arm32.
Signed-off-by: Julien Grall <[email protected]>
Reviewed-by: Michal Orzel <[email protected]>
with ...
---
xen/arch/arm/mmu/smpboot.c | 34 +++++++++++++++++++++++++++++-----
xen/arch/arm/xen.lds.S | 1 +
2 files changed, 30 insertions(+), 5 deletions(-)
diff --git a/xen/arch/arm/mmu/smpboot.c b/xen/arch/arm/mmu/smpboot.c
index b6fc0aae07f1..f1cf9252710c 100644
--- a/xen/arch/arm/mmu/smpboot.c
+++ b/xen/arch/arm/mmu/smpboot.c
@@ -9,6 +9,10 @@
#include <asm/setup.h>
+/* Override macros from asm/page.h to make them work with mfn_t */
+#undef virt_to_mfn
+#define virt_to_mfn(va) _mfn(__virt_to_mfn(va))
+
/*
* Static start-of-day pagetables that we use before the allocators
* are up. These are used by all CPUs during bringup before switching
@@ -44,7 +48,7 @@ DEFINE_BOOT_PAGE_TABLE(boot_second);
DEFINE_BOOT_PAGE_TABLES(boot_third, XEN_NR_ENTRIES(2));
/* Non-boot CPUs use this to find the correct pagetables. */
-uint64_t init_ttbr;
+uint64_t __section(".data.idmap") init_ttbr;
Do we need to keep the declaration in mmu/mm.h? This variable is only used in
this file
and in assembly, so maybe better to drop declaration and use asmlinkage instead?
I don't see the problem of keeping the declaration in mmu/mm.h. In any
case, this seems to be unrelated to this patch.
/* Clear a translation table and clean & invalidate the cache */
static void clear_table(void *table)
@@ -68,6 +72,27 @@ static void clear_boot_pagetables(void)
clear_table(boot_third);
}
+static void set_init_ttbr(lpae_t *root)
+{
+ /*
+ * init_ttbr is part of the identity mapping which is read-only. So
+ * We need to re-map the region so it can be updated
Would you mind fixing s/So We/So we/ and add a full stop after last sentence?
I can do that.
Cheers,
--
Julien Grall
