[xen master] xen/arm64: smpboot: Directly switch to the runtime page-tables

[patchbot@xxxxxxx]

commit dff17457c482dcb38b7caafd095334f461ef6d35
Author:     Julien Grall <jgrall@xxxxxxxxxx>
AuthorDate: Sun Apr 16 15:32:11 2023 +0100
Commit:     Julien Grall <jgrall@xxxxxxxxxx>
CommitDate: Wed Apr 19 19:39:58 2023 +0100

    xen/arm64: smpboot: Directly switch to the runtime page-tables
    
    Switching TTBR while the MMU is on is not safe. Now that the identity
    mapping will not clash with the rest of the memory layout, we can avoid
    creating temporary page-tables every time a CPU is brought up.
    
    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: Bertrand Marquis <bertrand.marquis@xxxxxxx>
    Tested-by: Henry Wang <Henry.Wang@xxxxxxx>
---
 xen/arch/arm/arm32/smpboot.c   |  4 ++++
 xen/arch/arm/arm64/head.S      | 29 +++++++++--------------------
 xen/arch/arm/arm64/smpboot.c   | 15 ++++++++++++++-
 xen/arch/arm/include/asm/smp.h |  1 +
 xen/arch/arm/smpboot.c         |  1 +
 5 files changed, 29 insertions(+), 21 deletions(-)

diff --git a/xen/arch/arm/arm32/smpboot.c b/xen/arch/arm/arm32/smpboot.c
index e7368665d5..518e9f9c7e 100644
--- a/xen/arch/arm/arm32/smpboot.c
+++ b/xen/arch/arm/arm32/smpboot.c
@@ -21,6 +21,10 @@ int arch_cpu_up(int cpu)
     return platform_cpu_up(cpu);
 }
 
+void arch_cpu_up_finish(void)
+{
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/arch/arm/arm64/head.S b/xen/arch/arm/arm64/head.S
index 19a53d0a03..f37133cf7c 100644
--- a/xen/arch/arm/arm64/head.S
+++ b/xen/arch/arm/arm64/head.S
@@ -308,6 +308,7 @@ real_start_efi:
         bl    check_cpu_mode
         bl    cpu_init
         bl    create_page_tables
+        load_paddr x0, boot_pgtable
         bl    enable_mmu
 
         /* We are still in the 1:1 mapping. Jump to the runtime Virtual 
Address. */
@@ -365,29 +366,14 @@ GLOBAL(init_secondary)
 #endif
         bl    check_cpu_mode
         bl    cpu_init
-        bl    create_page_tables
+        load_paddr x0, init_ttbr
+        ldr   x0, [x0]
         bl    enable_mmu
 
         /* We are still in the 1:1 mapping. Jump to the runtime Virtual 
Address. */
         ldr   x0, =secondary_switched
         br    x0
 secondary_switched:
-        /*
-         * Non-boot CPUs need to move on to the proper pagetables, which were
-         * setup in init_secondary_pagetables.
-         *
-         * XXX: This is not compliant with the Arm Arm.
-         */
-        ldr   x4, =init_ttbr         /* VA of TTBR0_EL2 stashed by CPU 0 */
-        ldr   x4, [x4]               /* Actual value */
-        dsb   sy
-        msr   TTBR0_EL2, x4
-        dsb   sy
-        isb
-        tlbi  alle2
-        dsb   sy                     /* Ensure completion of TLB flush */
-        isb
-
 #ifdef CONFIG_EARLY_PRINTK
         /* Use a virtual address to access the UART. */
         ldr   x23, =EARLY_UART_VIRTUAL_ADDRESS
@@ -672,9 +658,13 @@ ENDPROC(create_page_tables)
  * mapping. In other word, the caller is responsible to switch to the runtime
  * mapping.
  *
- * Clobbers x0 - x3
+ * Inputs:
+ *   x0 : Physical address of the page tables.
+ *
+ * Clobbers x0 - x4
  */
 enable_mmu:
+        mov   x4, x0
         PRINT("- Turning on paging -\r\n")
 
         /*
@@ -685,8 +675,7 @@ enable_mmu:
         dsb   nsh
 
         /* Write Xen's PT's paddr into TTBR0_EL2 */
-        load_paddr x0, boot_pgtable
-        msr   TTBR0_EL2, x0
+        msr   TTBR0_EL2, x4
         isb
 
         mrs   x0, SCTLR_EL2
diff --git a/xen/arch/arm/arm64/smpboot.c b/xen/arch/arm/arm64/smpboot.c
index 694fbf67e6..9637f42469 100644
--- a/xen/arch/arm/arm64/smpboot.c
+++ b/xen/arch/arm/arm64/smpboot.c
@@ -106,10 +106,23 @@ int __init arch_cpu_init(int cpu, struct dt_device_node 
*dn)
 
 int arch_cpu_up(int cpu)
 {
+    int rc;
+
     if ( !smp_enable_ops[cpu].prepare_cpu )
         return -ENODEV;
 
-    return smp_enable_ops[cpu].prepare_cpu(cpu);
+    update_identity_mapping(true);
+
+    rc = smp_enable_ops[cpu].prepare_cpu(cpu);
+    if ( rc )
+        update_identity_mapping(false);
+
+    return rc;
+}
+
+void arch_cpu_up_finish(void)
+{
+    update_identity_mapping(false);
 }
 
 /*
diff --git a/xen/arch/arm/include/asm/smp.h b/xen/arch/arm/include/asm/smp.h
index 8133d5c295..a37ca55bff 100644
--- a/xen/arch/arm/include/asm/smp.h
+++ b/xen/arch/arm/include/asm/smp.h
@@ -25,6 +25,7 @@ extern void noreturn stop_cpu(void);
 extern int arch_smp_init(void);
 extern int arch_cpu_init(int cpu, struct dt_device_node *dn);
 extern int arch_cpu_up(int cpu);
+extern void arch_cpu_up_finish(void);
 
 int cpu_up_send_sgi(int cpu);
 
diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 412ae22869..4a89b3a834 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -500,6 +500,7 @@ int __cpu_up(unsigned int cpu)
     init_data.cpuid = ~0;
     smp_up_cpu = MPIDR_INVALID;
     clean_dcache(smp_up_cpu);
+    arch_cpu_up_finish();
 
     if ( !cpu_online(cpu) )
     {
--
generated by git-patchbot for /home/xen/git/xen.git#master