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Subject[PATCH v5 1/2] arm64: kvm: allows kvm cpu hotplug
Date
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, especially, kexec from rebooting the system on a boot
core in 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 arm64-specific cpu hotplug hook any more.

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

Signed-off-by: AKASHI Takahiro <takahiro.akashi@linaro.org>
---
arch/arm/include/asm/kvm_host.h | 10 ++++++-
arch/arm/include/asm/kvm_mmu.h | 1 +
arch/arm/kvm/arm.c | 58 ++++++++++++-------------------------
arch/arm/kvm/mmu.c | 5 ++++
arch/arm64/include/asm/kvm_host.h | 11 ++++++-
arch/arm64/include/asm/kvm_mmu.h | 1 +
arch/arm64/include/asm/virt.h | 9 ++++++
arch/arm64/kvm/hyp-init.S | 33 +++++++++++++++++++++
arch/arm64/kvm/hyp.S | 32 +++++++++++++++++---
9 files changed, 114 insertions(+), 46 deletions(-)

diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
index d71607c..8b67e11 100644
--- a/arch/arm/include/asm/kvm_host.h
+++ b/arch/arm/include/asm/kvm_host.h
@@ -213,6 +213,15 @@ 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;
@@ -230,7 +239,6 @@ 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 405aa18..dc6fadf 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 d9631ec..6833d7c 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>
@@ -85,11 +84,6 @@ 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;
@@ -891,7 +885,7 @@ long kvm_arch_vm_ioctl(struct file *filp,
}
}

-static void cpu_init_hyp_mode(void *dummy)
+int kvm_arch_hardware_enable(void)
{
phys_addr_t boot_pgd_ptr;
phys_addr_t pgd_ptr;
@@ -899,6 +893,9 @@ static void cpu_init_hyp_mode(void *dummy)
unsigned long stack_page;
unsigned long vector_ptr;

+ if (__hyp_get_vectors() != hyp_default_vectors)
+ return 0;
+
/* Switch from the HYP stub to our own HYP init vector */
__hyp_set_vectors(kvm_get_idmap_vector());

@@ -909,34 +906,31 @@ static void cpu_init_hyp_mode(void *dummy)
vector_ptr = (unsigned long)__kvm_hyp_vector;

__cpu_init_hyp_mode(boot_pgd_ptr, pgd_ptr, hyp_stack_ptr, vector_ptr);
+
+ return 0;
}

-static int hyp_init_cpu_notify(struct notifier_block *self,
- unsigned long action, void *cpu)
+void kvm_arch_hardware_disable(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;

- return NOTIFY_OK;
-}
+ if (__hyp_get_vectors() == hyp_default_vectors)
+ return;

-static struct notifier_block hyp_init_cpu_nb = {
- .notifier_call = hyp_init_cpu_notify,
-};
+ 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);
+}

#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);
+ if (cmd == CPU_PM_EXIT && kvm_arm_get_running_vcpu()) {
+ kvm_arch_hardware_enable();
return NOTIFY_OK;
}

@@ -1038,11 +1032,6 @@ 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();
@@ -1116,26 +1105,15 @@ 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 1d5accb..ce5d0a2 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_host.h b/arch/arm64/include/asm/kvm_host.h
index f0f58c9..42cf627 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -192,6 +192,7 @@ struct kvm_vcpu *kvm_arm_get_running_vcpu(void);
struct kvm_vcpu * __percpu *kvm_get_running_vcpus(void);

u64 kvm_call_hyp(void *hypfn, ...);
+void kvm_call_reset(phys_addr_t boot_pgd_ptr, phys_addr_t phys_idmap_start);
void force_vm_exit(const cpumask_t *mask);
void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);

@@ -216,6 +217,15 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
hyp_stack_ptr, vector_ptr);
}

+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_reset(boot_pgd_ptr, phys_idmap_start);
+}
+
struct vgic_sr_vectors {
void *save_vgic;
void *restore_vgic;
@@ -244,7 +254,6 @@ static inline void vgic_arch_setup(const struct vgic_params *vgic)
}
}

-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/arm64/include/asm/kvm_mmu.h b/arch/arm64/include/asm/kvm_mmu.h
index 6150567..ff5a087 100644
--- a/arch/arm64/include/asm/kvm_mmu.h
+++ b/arch/arm64/include/asm/kvm_mmu.h
@@ -98,6 +98,7 @@ 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/include/asm/virt.h b/arch/arm64/include/asm/virt.h
index 3070096..8f59ca88 100644
--- a/arch/arm64/include/asm/virt.h
+++ b/arch/arm64/include/asm/virt.h
@@ -61,6 +61,15 @@
#define BOOT_CPU_MODE_EL1 (0xe11)
#define BOOT_CPU_MODE_EL2 (0xe12)

+/*
+ * HVC_RESET - Reset cpu in EL2 to initial state.
+ *
+ * @x0: entry address in trampoline code in va
+ * @x1: identical mapping page table in pa
+ */
+
+#define HVC_RESET 5
+
#ifndef __ASSEMBLY__

/*
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 2e67a48..1925163 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -139,6 +139,39 @@ merged:
eret
ENDPROC(__kvm_hyp_init)

+ /*
+ * x0: HYP boot pgd
+ * x1: HYP phys_idmap_start
+ */
+ENTRY(__kvm_hyp_reset)
+ /* We're in trampoline code in VA, switch back to boot page tables */
+ msr ttbr0_el2, x0
+ isb
+
+ /* Invalidate the old TLBs */
+ 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_EL2_FLAGS
+ bic x0, x0, x1 // Clear SCTL_M and etc
+ msr sctlr_el2, x0
+ isb
+
+ /* Install stub vectors */
+ adrp x0, __hyp_stub_vectors
+ add x0, x0, #:lo12:__hyp_stub_vectors
+ msr vbar_el2, x0
+
+ eret
+ENDPROC(__kvm_hyp_reset)
+
.ltorg

.popsection
diff --git a/arch/arm64/kvm/hyp.S b/arch/arm64/kvm/hyp.S
index fd085ec..afe6263 100644
--- a/arch/arm64/kvm/hyp.S
+++ b/arch/arm64/kvm/hyp.S
@@ -1136,6 +1136,11 @@ ENTRY(kvm_call_hyp)
ret
ENDPROC(kvm_call_hyp)

+ENTRY(kvm_call_reset)
+ hvc #HVC_RESET
+ ret
+ENDPROC(kvm_call_reset)
+
.macro invalid_vector label, target
.align 2
\label:
@@ -1179,10 +1184,27 @@ el1_sync: // Guest trapped into EL2
cmp x18, #HVC_GET_VECTORS
b.ne 1f
mrs x0, vbar_el2
- b 2f
-
-1: /* Default to HVC_CALL_HYP. */
+ b do_eret

+ /* jump into trampoline code */
+1: cmp x18, #HVC_RESET
+ b.ne 2f
+ /*
+ * Entry point is:
+ * TRAMPOLINE_VA
+ * + (__kvm_hyp_reset - (__hyp_idmap_text_start & PAGE_MASK))
+ */
+ adrp x2, __kvm_hyp_reset
+ add x2, x2, #:lo12:__kvm_hyp_reset
+ adrp x3, __hyp_idmap_text_start
+ add x3, x3, #:lo12:__hyp_idmap_text_start
+ and x3, x3, PAGE_MASK
+ sub x2, x2, x3
+ ldr x3, =TRAMPOLINE_VA
+ add x2, x2, x3
+ br x2 // no return
+
+2: /* Default to HVC_CALL_HYP. */
push lr, xzr

/*
@@ -1196,7 +1218,9 @@ el1_sync: // Guest trapped into EL2
blr lr

pop lr, xzr
-2: eret
+
+do_eret:
+ eret

el1_trap:
/*
--
1.7.9.5


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