On 16/01/2023 08:14, Michal Orzel wrote:
Hi Julien,
Hi Luca,
On 13/01/2023 11:11, Julien Grall wrote:
+/*
+ * Remove the temporary mapping of Xen starting at TEMPORARY_XEN_VIRT_START.
+ *
+ * Clobbers r0 - r1
+ */
+remove_temporary_mapping:
+ /* r2:r3 := invalid page-table entry */
+ mov r2, #0
+ mov r3, #0
+
+ adr_l r0, boot_pgtable
+ mov_w r1, TEMPORARY_XEN_VIRT_START
+ get_table_slot r1, r1, 1 /* r1 := first slot */
Can't we just use TEMPORARY_AREA_FIRST_SLOT?
IMHO, it would make the code a bit more difficult to read because the
connection between TEMPORARY_XEN_VIRT_START and
TEMPORARY_AREA_FIRST_SLOT is not totally obvious.
So I would rather prefer if this stays like that.
+ lsl r1, r1, #3 /* r1 := first slot offset */
+ strd r2, r3, [r0, r1]
+
+ flush_xen_tlb_local r0
+
+ mov pc, lr
+ENDPROC(remove_temporary_mapping)
+
/*
* Map the UART in the fixmap (when earlyprintk is used) and hook the
* fixmap table in the page tables.
diff --git a/xen/arch/arm/include/asm/config.h
b/xen/arch/arm/include/asm/config.h
index 87851e677701..6c1b762e976d 100644
--- a/xen/arch/arm/include/asm/config.h
+++ b/xen/arch/arm/include/asm/config.h
@@ -148,6 +148,20 @@
/* Number of domheap pagetable pages required at the second level (2MB
mappings) */
#define DOMHEAP_SECOND_PAGES (DOMHEAP_VIRT_SIZE >> FIRST_SHIFT)
+/*
+ * The temporary area is overlapping with the domheap area. This may
+ * be used to create an alias of the first slot containing Xen mappings
+ * when turning on/off the MMU.
+ */
+#define TEMPORARY_AREA_FIRST_SLOT (first_table_offset(DOMHEAP_VIRT_START))
+
+/* Calculate the address in the temporary area */
+#define TEMPORARY_AREA_ADDR(addr) \
+ (((addr) & ~XEN_PT_LEVEL_MASK(1)) | \
+ (TEMPORARY_AREA_FIRST_SLOT << XEN_PT_LEVEL_SHIFT(1)))
XEN_PT_LEVEL_{MASK/SHIFT} should be used when we do not know the level upfront.
Otherwise, no need for opencoding and you should use FIRST_MASK and FIRST_SHIFT.
We discussed in the past to phase out the use of FIRST_MASK, FIRST_SHIFT
because the name is too generic. So for new code, we should use
XEN_PT_LEVEL_{MASK/SHIFT}.
Cheers,
--
Julien Grall
