[PATCH v15 05/20] arm64: kvm: allows kvm cpu hotplug

Geoff Levand
2016-03-14T17:48:00Z

From: AKASHI Takahiro <takahiro.akashi@linaro.org>

The current kvm implementation on arm64 does cpu-specific initialization
at system boot, and has no way to gracefully shutdown a core in terms of
kvm. This prevents kexec from rebooting the system at EL2.

This patch adds a cpu tear-down function and also puts an existing cpu-init
code into a separate function, kvm_arch_hardware_disable() and
kvm_arch_hardware_enable() respectively.
We don't need the arm64 specific cpu hotplug hook any more.

Since this patch modifies common code between arm and arm64, one stub
definition, __cpu_reset_hyp_mode(), is added on arm side to avoid
compilation errors.

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
[Moved __kvm_hyp_reset() to use kvm_call_hyp(), instead of having its own
dedicated entry point in el1_sync. Added some comments and a tlbi.]
Signed-off-by: James Morse <james.morse@arm.com>
---
arch/arm/include/asm/kvm_host.h | 10 +++-
arch/arm/include/asm/kvm_mmu.h | 1 +
arch/arm/kvm/arm.c | 104 ++++++++++++++++++++++++--------------
arch/arm/kvm/mmu.c | 5 ++
arch/arm64/include/asm/kvm_asm.h | 1 +
arch/arm64/include/asm/kvm_host.h | 12 ++++-
arch/arm64/include/asm/kvm_mmu.h | 1 +
arch/arm64/kvm/hyp-init.S | 42 +++++++++++++++
arch/arm64/kvm/reset.c | 14 +++++
9 files changed, 150 insertions(+), 40 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index f9f2779..8af531d 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -220,6 +220,15 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
kvm_call_hyp((void*)hyp_stack_ptr, vector_ptr, pgd_ptr);
}

+static inline void __cpu_reset_hyp_mode(phys_addr_t boot_pgd_ptr,
+ phys_addr_t phys_idmap_start)
+{
+ /*
+ * TODO
+ * kvm_call_reset(boot_pgd_ptr, phys_idmap_start);
+ */
+}
+
static inline int kvm_arch_dev_ioctl_check_extension(long ext)
{
return 0;
@@ -232,7 +241,6 @@ void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);

struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);

-static inline void kvm_arch_hardware_disable(void) {}
static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
diff --git a/arch/arm/include/asm/kvm_mmu.h b/arch/arm/include/asm/kvm_mmu.h
index a520b79..4fd9ddb 100644
--- a/arch/arm/include/asm/kvm_mmu.h
+++ b/arch/arm/include/asm/kvm_mmu.h
@@ -66,6 +66,7 @@ void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
phys_addr_t kvm_mmu_get_httbr(void);
phys_addr_t kvm_mmu_get_boot_httbr(void);
phys_addr_t kvm_get_idmap_vector(void);
+phys_addr_t kvm_get_idmap_start(void);
int kvm_mmu_init(void);
void kvm_clear_hyp_idmap(void);

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index dda1959..0aad49f 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -16,7 +16,6 @@
* Foundation, 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

-#include <linux/cpu.h>
#include <linux/cpu_pm.h>
#include <linux/errno.h>
#include <linux/err.h>
@@ -65,6 +64,8 @@ static DEFINE_SPINLOCK(kvm_vmid_lock);

static bool vgic_present;

+static DEFINE_PER_CPU(unsigned char, kvm_arm_hardware_enabled);
+
static void kvm_arm_set_running_vcpu(struct kvm_vcpu *vcpu)
{
BUG_ON(preemptible());
@@ -89,11 +90,6 @@ struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void)
return &kvm_arm_running_vcpu;
}

-int kvm_arch_hardware_enable(void)
-{
- return 0;
-}
-
int kvm_arch_vcpu_should_kick(struct kvm_vcpu *vcpu)
{
return kvm_vcpu_exiting_guest_mode(vcpu) == IN_GUEST_MODE;
@@ -585,7 +581,13 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
/*
* Re-check atomic conditions
*/
- if (signal_pending(current)) {
+ if (unlikely(!__this_cpu_read(kvm_arm_hardware_enabled))) {
+ /* cpu has been torn down */
+ ret = 0;
+ run->exit_reason = KVM_EXIT_FAIL_ENTRY;
+ run->fail_entry.hardware_entry_failure_reason
+ = (u64)-ENOEXEC;
+ } else if (signal_pending(current)) {
ret = -EINTR;
run->exit_reason = KVM_EXIT_INTR;
}
@@ -967,7 +969,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
}
}

-static void cpu_init_hyp_mode(void *dummy)
+static void cpu_init_hyp_mode(void)
{
phys_addr_t boot_pgd_ptr;
phys_addr_t pgd_ptr;
@@ -989,36 +991,67 @@ static void cpu_init_hyp_mode(void *dummy)
kvm_arm_init_debug();
}

-static int hyp_init_cpu_notify(struct notifier_block *self,
- unsigned long action, void *cpu)
+static void cpu_reset_hyp_mode(void)
{
- switch (action) {
- case CPU_STARTING:
- case CPU_STARTING_FROZEN:
- if (__hyp_get_vectors() == hyp_default_vectors)
- cpu_init_hyp_mode(NULL);
- break;
+ phys_addr_t boot_pgd_ptr;
+ phys_addr_t phys_idmap_start;
+
+ boot_pgd_ptr = kvm_mmu_get_boot_httbr();
+ phys_idmap_start = kvm_get_idmap_start();
+
+ __cpu_reset_hyp_mode(boot_pgd_ptr, phys_idmap_start);
+}
+
+int kvm_arch_hardware_enable(void)
+{
+ if (!__this_cpu_read(kvm_arm_hardware_enabled)) {
+ cpu_init_hyp_mode();
+ __this_cpu_write(kvm_arm_hardware_enabled, 1);
}

- return NOTIFY_OK;
+ return 0;
}

-static struct notifier_block hyp_init_cpu_nb = {
- .notifier_call = hyp_init_cpu_notify,
-};
+void kvm_arch_hardware_disable(void)
+{
+ if (!__this_cpu_read(kvm_arm_hardware_enabled))
+ return;
+
+ cpu_reset_hyp_mode();
+ __this_cpu_write(kvm_arm_hardware_enabled, 0);
+}

#ifdef CONFIG_CPU_PM
static int hyp_init_cpu_pm_notifier(struct notifier_block *self,
unsigned long cmd,
void *v)
{
- if (cmd == CPU_PM_EXIT &&
- __hyp_get_vectors() == hyp_default_vectors) {
- cpu_init_hyp_mode(NULL);
+ /*
+ * kvm_arm_hardware_enabled is left with its old value over
+ * PM_ENTER->PM_EXIT. It is used to indicate PM_EXIT should
+ * re-enable hyp.
+ */
+ switch (cmd) {
+ case CPU_PM_ENTER:
+ if (__this_cpu_read(kvm_arm_hardware_enabled))
+ /*
+ * don't update kvm_arm_hardware_enabled here
+ * so that the hardware will be re-enabled
+ * when we resume. See below.
+ */
+ cpu_reset_hyp_mode();
+
+ return NOTIFY_OK;
+ case CPU_PM_EXIT:
+ if (__this_cpu_read(kvm_arm_hardware_enabled))
+ /* The hardware was enabled before suspend. */
+ cpu_init_hyp_mode();
+
return NOTIFY_OK;
- }

- return NOTIFY_DONE;
+ default:
+ return NOTIFY_DONE;
+ }
}

static struct notifier_block hyp_init_cpu_pm_nb = {
@@ -1122,14 +1155,20 @@ static int init_hyp_mode(void)
}

/*
- * Execute the init code on each CPU.
+ * Init this CPU temporarily to execute kvm_hyp_call()
+ * during kvm_vgic_hyp_init().
*/
- on_each_cpu(cpu_init_hyp_mode, NULL, 1);
+ preempt_disable();
+ cpu_init_hyp_mode();

/*
* Init HYP view of VGIC
*/
err = kvm_vgic_hyp_init();
+
+ cpu_reset_hyp_mode();
+ preempt_enable();
+
switch (err) {
case 0:
vgic_present = true;
@@ -1213,26 +1252,15 @@ int kvm_arch_init(void *opaque)
}
}

- cpu_notifier_register_begin();
-
err = init_hyp_mode();
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;
- }
-
- cpu_notifier_register_done();
-
hyp_cpu_pm_init();

kvm_coproc_table_init();
return 0;
out_err:
- cpu_notifier_register_done();
return err;
}

diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index aba61fd..7a3aed6 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -1643,6 +1643,11 @@ phys_addr_t kvm_get_idmap_vector(void)
return hyp_idmap_vector;
}

+phys_addr_t kvm_get_idmap_start(void)
+{
+ return hyp_idmap_start;
+}
+
int kvm_mmu_init(void)
{
int err;
diff --git a/arch/arm64/include/asm/kvm_asm.h b/arch/arm64/include/asm/kvm_asm.h
index 52b777b..4191d12 100644
--- a/arch/arm64/include/asm/kvm_asm.h
+++ b/arch/arm64/include/asm/kvm_asm.h
@@ -32,6 +32,7 @@ struct kvm_vcpu;

extern char __kvm_hyp_init[];
extern char __kvm_hyp_init_end[];
+extern char __kvm_hyp_reset[];

extern char __kvm_hyp_vector[];

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 689d4c9..b218211 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -44,6 +44,7 @@
int __attribute_const__ kvm_target_cpu(void);
int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
int kvm_arch_dev_ioctl_check_extension(long ext);
+phys_addr_t kvm_hyp_reset_entry(void);

struct kvm_arch {
/* The VMID generation used for the virt. memory system */
@@ -332,7 +333,16 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
hyp_stack_ptr, vector_ptr);
}

-static inline void kvm_arch_hardware_disable(void) {}
+static inline void __cpu_reset_hyp_mode(phys_addr_t boot_pgd_ptr,
+ phys_addr_t phys_idmap_start)
+{
+ /*
+ * Call reset code, and switch back to stub hyp vectors.
+ */
+ kvm_call_hyp((void *)kvm_hyp_reset_entry(),
+ boot_pgd_ptr, phys_idmap_start);
+}
+
static inline void kvm_arch_hardware_unsetup(void) {}
static inline void kvm_arch_sync_events(struct kvm *kvm) {}
static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
diff --git a/arch/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 7364339..7ee6824 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -99,6 +99,7 @@ void kvm_mmu_free_memory_caches(struct kvm_vcpu *vcpu);
phys_addr_t kvm_mmu_get_httbr(void);
phys_addr_t kvm_mmu_get_boot_httbr(void);
phys_addr_t kvm_get_idmap_vector(void);
+phys_addr_t kvm_get_idmap_start(void);
int kvm_mmu_init(void);
void kvm_clear_hyp_idmap(void);

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 034d152c..a19a7ef 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -152,6 +152,48 @@ merged:
eret
ENDPROC(__kvm_hyp_init)

+ /*
+ * x0: HYP boot pgd
+ * x1: HYP phys_idmap_start
+ */
+ENTRY(__kvm_hyp_reset)
+ /*
+ * Retrieve lr from the stack (pushed by el1_sync()), so we can eret
+ * from here.
+ */
+ ldp lr, xzr, [sp], #16
+
+ /* We're in trampoline code in VA, switch back to boot page tables */
+ msr ttbr0_el2, x0
+ isb
+
+ /* Ensure the PA branch doesn't find a stale tlb entry. */
+ tlbi alle2
+ dsb sy
+
+ /* Branch into PA space */
+ adr x0, 1f
+ bfi x1, x0, #0, #PAGE_SHIFT
+ br x1
+
+ /* We're now in idmap, disable MMU */
+1: mrs x0, sctlr_el2
+ ldr x1, =SCTLR_ELx_FLAGS
+ bic x0, x0, x1 // Clear SCTL_M and etc
+ msr sctlr_el2, x0
+ isb
+
+ /* Invalidate the old TLBs */
+ tlbi alle2
+ dsb sy
+
+ /* Install stub vectors */
+ adr_l x0, __hyp_stub_vectors
+ msr vbar_el2, x0
+
+ eret
+ENDPROC(__kvm_hyp_reset)
+
.ltorg

.popsection
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index f34745c..d6e155a 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -29,7 +29,9 @@
#include <asm/cputype.h>
#include <asm/ptrace.h>
#include <asm/kvm_arm.h>
+#include <asm/kvm_asm.h>
#include <asm/kvm_coproc.h>
+#include <asm/kvm_mmu.h>

/*
* ARMv8 Reset Values
@@ -123,3 +125,15 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
/* Reset timer */
return kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
}
+
+extern char __hyp_idmap_text_start[];
+
+phys_addr_t kvm_hyp_reset_entry(void)
+{
+ unsigned long offset;
+
+ offset = (unsigned long)__kvm_hyp_reset
+ - ((unsigned long)__hyp_idmap_text_start & PAGE_MASK);
+
+ return TRAMPOLINE_VA + offset;
+}
--
2.5.0