From 21cf953a03d54e6ca01a39f52637d79134ad4e0e Mon Sep 17 00:00:00 2001
From: Dominique Martinet <dominique.martinet@cea.fr>
Date: Wed, 6 Feb 2019 16:55:14 +0900
Subject: [PATCH] x86: disable zero mapping and add a boot pt for ap trampoline

the application processor trampoline needs the trampoline physical
address to be mapped for the few instructions between loading the
page table and jumping to normal memory area; setup a new pt for them.

Also make it use its stack where it needs to be directly.

With that, x86 can finally remove the 0 page from its init mapping

Change-Id: Iab3f33a2ed22570eeb47b5ab6e068c9a17c25413
---
 arch/x86_64/kernel/cpu.c              |  8 ++++++--
 arch/x86_64/kernel/include/cpulocal.h |  1 +
 arch/x86_64/kernel/local.c            |  2 +-
 arch/x86_64/kernel/memory.c           | 16 +++++++++++++++-
 4 files changed, 23 insertions(+), 4 deletions(-)

diff --git a/arch/x86_64/kernel/cpu.c b/arch/x86_64/kernel/cpu.c
index 1fbcdf9d..95879c4c 100644
--- a/arch/x86_64/kernel/cpu.c
+++ b/arch/x86_64/kernel/cpu.c
@@ -824,11 +824,14 @@ void call_ap_func(void (*next_func)(void))
 	next_func();
 }
 
+struct page_table *get_init_page_table(void);
 void setup_x86_ap(void (*next_func)(void))
 {
 	unsigned long rsp;
 	cpu_disable_interrupt();
 
+	ihk_mc_load_page_table(get_init_page_table());
+
 	assign_processor_id();
 
 	init_smp_processor();
@@ -1246,7 +1249,7 @@ void ihk_mc_set_page_fault_handler(void (*h)(void *, uint64_t, void *))
 }
 
 extern char trampoline_code_data[], trampoline_code_data_end[];
-struct page_table *get_init_page_table(void);
+struct page_table *get_boot_page_table(void);
 unsigned long get_transit_page_table(void);
 
 /* reusable, but not reentrant */
@@ -1270,9 +1273,10 @@ void ihk_mc_boot_cpu(int cpuid, unsigned long pc)
 	memcpy(p, trampoline_code_data, 
 	       trampoline_code_data_end - trampoline_code_data);
 
-	p[1] = (unsigned long)virt_to_phys(get_init_page_table());
+	p[1] = (unsigned long)virt_to_phys(get_boot_page_table());
 	p[2] = (unsigned long)setup_x86_ap;
 	p[3] = pc;
+	p[4] = (unsigned long)get_x86_cpu_local_kstack(cpuid);
 	p[6] = (unsigned long)get_transit_page_table();
 	if (!p[6]) {
 		p[6] = p[1];
diff --git a/arch/x86_64/kernel/include/cpulocal.h b/arch/x86_64/kernel/include/cpulocal.h
index 8c4eb1e7..66cf69c1 100644
--- a/arch/x86_64/kernel/include/cpulocal.h
+++ b/arch/x86_64/kernel/include/cpulocal.h
@@ -50,6 +50,7 @@ struct x86_cpu_local_variables {
 
 struct x86_cpu_local_variables *get_x86_cpu_local_variable(int id);
 struct x86_cpu_local_variables *get_x86_this_cpu_local(void);
+void *get_x86_cpu_local_kstack(int id);
 void *get_x86_this_cpu_kstack(void);
 
 
diff --git a/arch/x86_64/kernel/local.c b/arch/x86_64/kernel/local.c
index 3ca416d9..aa74fc9c 100644
--- a/arch/x86_64/kernel/local.c
+++ b/arch/x86_64/kernel/local.c
@@ -49,7 +49,7 @@ struct x86_cpu_local_variables *get_x86_cpu_local_variable(int id)
 		((char *)locals + (LOCALS_SPAN * id));
 }
 
-static void *get_x86_cpu_local_kstack(int id)
+void *get_x86_cpu_local_kstack(int id)
 {
 	return ((char *)locals + (LOCALS_SPAN * (id + 1)));
 }
diff --git a/arch/x86_64/kernel/memory.c b/arch/x86_64/kernel/memory.c
index 751b892c..8db9043e 100644
--- a/arch/x86_64/kernel/memory.c
+++ b/arch/x86_64/kernel/memory.c
@@ -108,6 +108,7 @@ struct page_table {
 };
 
 static struct page_table *init_pt;
+static struct page_table *boot_pt;
 static int init_pt_loaded = 0;
 static ihk_spinlock_t init_pt_lock;
 
@@ -2519,6 +2520,11 @@ struct page_table *get_init_page_table(void)
 	return init_pt;
 }
 
+struct page_table *get_boot_page_table(void)
+{
+	return boot_pt;
+}
+
 static unsigned long fixed_virt;
 static void init_fixed_area(struct page_table *pt)
 {
@@ -2695,10 +2701,18 @@ void init_page_table(void)
 	init_normal_area(init_pt);
 	init_linux_kernel_mapping(init_pt);
 	init_fixed_area(init_pt);
-	init_low_area(init_pt);
 	init_text_area(init_pt);
 	init_vsyscall_area(init_pt);
 
+	/* boot page table: needs zero mapping in order to execute the next
+	 * instruction that jumps into regular regions
+	 */
+	boot_pt = ihk_mc_alloc_pages(1, IHK_MC_AP_CRITICAL);
+	memcpy(boot_pt, init_pt, sizeof(*boot_pt));
+	init_low_area(boot_pt);
+	if (memcmp(init_pt, boot_pt, sizeof(*init_pt)) == 0)
+		panic("init low area for boot pt did not affect toplevel entry");
+
 	load_page_table(init_pt);
 	init_pt_loaded = 1;
 	kprintf("Page table is now at 0x%lx\n", init_pt);