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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen master] xen/arm64: mm: Rework switch_ttbr()
commit c4b72c4a54809cb76d652cc2ffe2fce90afd017e
Author: Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Sun Apr 16 15:32:10 2023 +0100
Commit: Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Wed Apr 19 19:39:58 2023 +0100
xen/arm64: mm: Rework switch_ttbr()
At the moment, switch_ttbr() is switching the TTBR whilst the MMU is
still on.
Switching TTBR is like replacing existing mappings with new ones. So
we need to follow the break-before-make sequence.
In this case, it means the MMU needs to be switched off while the
TTBR is updated. In order to disable the MMU, we need to first
jump to an identity mapping.
Rename switch_ttbr() to switch_ttbr_id() and create an helper on
top to temporary map the identity mapping and call switch_ttbr()
via the identity address.
switch_ttbr_id() is now reworked to temporarily turn off the MMU
before updating the TTBR.
We also need to make sure the helper switch_ttbr() is part of the
identity mapping. So move _end_boot past it.
The arm32 code will use a different approach. So this issue is for now
only resolved on arm64.
Signed-off-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Luca Fancellu <luca.fancellu@xxxxxxx>
Reviewed-by: Michal Orzel <michal.orzel@xxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
---
xen/arch/arm/arm64/head.S | 50 ++++++++++++++++++++++++++++---------------
xen/arch/arm/arm64/mm.c | 31 +++++++++++++++++++++++++++
xen/arch/arm/include/asm/mm.h | 2 ++
xen/arch/arm/mm.c | 2 --
4 files changed, 66 insertions(+), 19 deletions(-)
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 76c3affe11..19a53d0a03 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -816,30 +816,46 @@ ENDPROC(fail)
* Switch TTBR
*
* x0 ttbr
- *
- * TODO: This code does not comply with break-before-make.
*/
-ENTRY(switch_ttbr)
- dsb sy /* Ensure the flushes happen before
- * continuing */
- isb /* Ensure synchronization with previous
- * changes to text */
- tlbi alle2 /* Flush hypervisor TLB */
- ic iallu /* Flush I-cache */
- dsb sy /* Ensure completion of TLB flush */
+ENTRY(switch_ttbr_id)
+ /* 1) Ensure any previous read/write have completed */
+ dsb ish
+ isb
+
+ /* 2) Turn off MMU */
+ mrs x1, SCTLR_EL2
+ bic x1, x1, #SCTLR_Axx_ELx_M
+ msr SCTLR_EL2, x1
+ isb
+
+ /*
+ * 3) Flush the TLBs.
+ * See asm/arm64/flushtlb.h for the explanation of the sequence.
+ */
+ dsb nshst
+ tlbi alle2
+ dsb nsh
+ isb
+
+ /* 4) Update the TTBR */
+ msr TTBR0_EL2, x0
isb
- msr TTBR0_EL2, x0
+ /*
+ * 5) Flush I-cache
+ * This should not be necessary but it is kept for safety.
+ */
+ ic iallu
+ isb
- isb /* Ensure synchronization with previous
- * changes to text */
- tlbi alle2 /* Flush hypervisor TLB */
- ic iallu /* Flush I-cache */
- dsb sy /* Ensure completion of TLB flush */
+ /* 6) Turn on the MMU */
+ mrs x1, SCTLR_EL2
+ orr x1, x1, #SCTLR_Axx_ELx_M /* Enable MMU */
+ msr SCTLR_EL2, x1
isb
ret
-ENDPROC(switch_ttbr)
+ENDPROC(switch_ttbr_id)
#ifdef CONFIG_EARLY_PRINTK
/*
diff --git a/xen/arch/arm/arm64/mm.c b/xen/arch/arm/arm64/mm.c
index 56b9e9b8d3..78b7c7eb00 100644
--- a/xen/arch/arm/arm64/mm.c
+++ b/xen/arch/arm/arm64/mm.c
@@ -120,6 +120,37 @@ void update_identity_mapping(bool enable)
BUG_ON(rc);
}
+extern void switch_ttbr_id(uint64_t ttbr);
+
+typedef void (switch_ttbr_fn)(uint64_t ttbr);
+
+void __init switch_ttbr(uint64_t ttbr)
+{
+ vaddr_t id_addr = virt_to_maddr(switch_ttbr_id);
+ switch_ttbr_fn *fn = (switch_ttbr_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)switch_ttbr_id);
+ pte.pt.table = 1;
+ pte.pt.xn = 0;
+ pte.pt.ro = 1;
+ write_pte(&xen_third_id[third_table_offset(id_addr)], pte);
+
+ /* Switch TTBR */
+ fn(ttbr);
+
+ /*
+ * 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);
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/arm/include/asm/mm.h b/xen/arch/arm/include/asm/mm.h
index 23dec574eb..4262165ce2 100644
--- a/xen/arch/arm/include/asm/mm.h
+++ b/xen/arch/arm/include/asm/mm.h
@@ -207,6 +207,8 @@ extern unsigned long total_pages;
extern void setup_pagetables(unsigned long boot_phys_offset);
/* Map FDT in boot pagetable */
extern void *early_fdt_map(paddr_t fdt_paddr);
+/* Switch to a new root page-tables */
+extern void switch_ttbr(uint64_t ttbr);
/* Remove early mappings */
extern void remove_early_mappings(void);
/* Allocate and initialise pagetables for a secondary CPU. Sets init_ttbr to
the
diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
index b7104d8d33..74f6ff2c6f 100644
--- a/xen/arch/arm/mm.c
+++ b/xen/arch/arm/mm.c
@@ -488,8 +488,6 @@ static void xen_pt_enforce_wnx(void)
flush_xen_tlb_local();
}
-extern void switch_ttbr(uint64_t ttbr);
-
/* Clear a translation table and clean & invalidate the cache */
static void clear_table(void *table)
{
--
generated by git-patchbot for /home/xen/git/xen.git#master
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