ARM: KVM: perform HYP initilization for hotplugged CPUs

Now that we have the necessary infrastructure to boot a hotplugged CPU
at any point in time, wire a CPU notifier that will perform the HYP
init for the incoming CPU.

Note that this depends on the platform code and/or firmware to boot the
incoming CPU with HYP mode enabled and return to the kernel by following
the normal boot path (HYP stub installed).

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@cs.columbia.edu>

3 files changed, 63 insertions, 22 deletions

diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index 24b767a8cdb9..472ac7091003 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -44,6 +44,7 @@
 
 int create_hyp_mappings(void *from, void *to);
 int create_hyp_io_mappings(void *from, void *to, phys_addr_t);
+void free_boot_hyp_pgd(void);
 void free_hyp_pgds(void);
 
 int kvm_alloc_stage2_pgd(struct kvm *kvm);
diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index fc47bd721ab0..6ea2aed0d29f 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -16,6 +16,7 @@
  * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
+#include <linux/cpu.h>
 #include <linux/errno.h>
 #include <linux/err.h>
 #include <linux/kvm_host.h>
@@ -785,7 +786,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
         }
 }
 
-static void cpu_init_hyp_mode(void *vector)
+static void cpu_init_hyp_mode(void *dummy)
 {
         unsigned long long boot_pgd_ptr;
         unsigned long long pgd_ptr;
@@ -805,12 +806,28 @@ static void cpu_init_hyp_mode(void *vector)
         __cpu_init_hyp_mode(boot_pgd_ptr, pgd_ptr, hyp_stack_ptr, vector_ptr);
 }
 
+static int hyp_init_cpu_notify(struct notifier_block *self,
+                               unsigned long action, void *cpu)
+{
+        switch (action) {
+        case CPU_STARTING:
+        case CPU_STARTING_FROZEN:
+                cpu_init_hyp_mode(NULL);
+                break;
+        }
+
+        return NOTIFY_OK;
+}
+
+static struct notifier_block hyp_init_cpu_nb = {
+        .notifier_call = hyp_init_cpu_notify,
+};
+
 /**
  * Inits Hyp-mode on all online CPUs
  */
 static int init_hyp_mode(void)
 {
-        phys_addr_t init_phys_addr;
         int cpu;
         int err = 0;
 
@@ -843,19 +860,6 @@ static int init_hyp_mode(void)
         }
 
         /*
-         * Execute the init code on each CPU.
-         *
-         * Note: The stack is not mapped yet, so don't do anything else than
-         * initializing the hypervisor mode on each CPU using a local stack
-         * space for temporary storage.
-         */
-        init_phys_addr = virt_to_phys(__kvm_hyp_init);
-        for_each_online_cpu(cpu) {
-                smp_call_function_single(cpu, cpu_init_hyp_mode,
-                                         (void *)(long)init_phys_addr, 1);
-        }
-
-        /*
          * Map the Hyp-code called directly from the host
          */
         err = create_hyp_mappings(__kvm_hyp_code_start, __kvm_hyp_code_end);
@@ -900,6 +904,11 @@ static int init_hyp_mode(void)
         }
 
         /*
+         * Execute the init code on each CPU.
+         */
+        on_each_cpu(cpu_init_hyp_mode, NULL, 1);
+
+        /*
          * Init HYP view of VGIC
          */
         err = kvm_vgic_hyp_init();
@@ -917,6 +926,10 @@ static int init_hyp_mode(void)
         if (err)
                 goto out_free_mappings;
 
+#ifndef CONFIG_HOTPLUG_CPU
+        free_boot_hyp_pgd();
+#endif
+
         kvm_perf_init();
 
         kvm_info("Hyp mode initialized successfully\n");
@@ -955,6 +968,12 @@ int kvm_arch_init(void *opaque)
         if (err)
                 goto out_err;
 
+        err = register_cpu_notifier(&hyp_init_cpu_nb);
+        if (err) {
+                kvm_err("Cannot register HYP init CPU notifier (%d)\n", err);
+                goto out_err;
+        }
+
         kvm_coproc_table_init();
         return 0;
 out_err:
diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index 4646c17f571c..965706578f13 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -156,6 +156,31 @@ static void unmap_range(pgd_t *pgdp, unsigned long long start, u64 size)
 }
 
 /**
+ * free_boot_hyp_pgd - free HYP boot page tables
+ *
+ * Free the HYP boot page tables. The bounce page is also freed.
+ */
+void free_boot_hyp_pgd(void)
+{
+        mutex_lock(&kvm_hyp_pgd_mutex);
+
+        if (boot_hyp_pgd) {
+                unmap_range(boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
+                unmap_range(boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
+                kfree(boot_hyp_pgd);
+                boot_hyp_pgd = NULL;
+        }
+
+        if (hyp_pgd)
+                unmap_range(hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
+
+        kfree(init_bounce_page);
+        init_bounce_page = NULL;
+
+        mutex_unlock(&kvm_hyp_pgd_mutex);
+}
+
+/**
  * free_hyp_pgds - free Hyp-mode page tables
  *
  * Assumes hyp_pgd is a page table used strictly in Hyp-mode and
@@ -169,13 +194,9 @@ void free_hyp_pgds(void)
 {
         unsigned long addr;
 
-        mutex_lock(&kvm_hyp_pgd_mutex);
+        free_boot_hyp_pgd();
 
-        if (boot_hyp_pgd) {
-                unmap_range(boot_hyp_pgd, hyp_idmap_start, PAGE_SIZE);
-                unmap_range(boot_hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE);
-                kfree(boot_hyp_pgd);
-        }
+        mutex_lock(&kvm_hyp_pgd_mutex);
 
         if (hyp_pgd) {
                 for (addr = PAGE_OFFSET; virt_addr_valid(addr); addr += PGDIR_SIZE)
@@ -183,9 +204,9 @@ void free_hyp_pgds(void)
                 for (addr = VMALLOC_START; is_vmalloc_addr((void*)addr); addr += PGDIR_SIZE)
                         unmap_range(hyp_pgd, KERN_TO_HYP(addr), PGDIR_SIZE);
                 kfree(hyp_pgd);
+                hyp_pgd = NULL;
         }
 
-        kfree(init_bounce_page);
         mutex_unlock(&kvm_hyp_pgd_mutex);
 }