[PATCH 09/15] arm64: KVM: Simplify HYP init/teardown

Marc Zyngier
2016-06-07T10:58:29Z

Now that we only have the "merged page tables" case to deal with,
there is a bunch of things we can simplify in the HYP code (both
at init and teardown time).

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
arch/arm64/include/asm/kvm_host.h | 12 ++------
arch/arm64/kvm/hyp-init.S | 61 +++++----------------------------------
arch/arm64/kvm/hyp/entry.S | 19 ------------
arch/arm64/kvm/hyp/hyp-entry.S | 15 ++++++++++
arch/arm64/kvm/reset.c | 11 -------
5 files changed, 26 insertions(+), 92 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 49095fc..88462c3 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -48,7 +48,6 @@
int __attribute_const__ kvm_target_cpu(void);
int kvm_reset_vcpu(struct kvm_vcpu *vcpu);
int kvm_arch_dev_ioctl_check_extension(long ext);
-unsigned long kvm_hyp_reset_entry(void);
void __extended_idmap_trampoline(phys_addr_t boot_pgd, phys_addr_t idmap_start);

struct kvm_arch {
@@ -357,19 +356,14 @@ static inline void __cpu_init_hyp_mode(phys_addr_t boot_pgd_ptr,
* Call initialization code, and switch to the full blown
* HYP code.
*/
- __kvm_call_hyp((void *)boot_pgd_ptr, pgd_ptr,
- hyp_stack_ptr, vector_ptr);
+ __kvm_call_hyp((void *)pgd_ptr, hyp_stack_ptr, vector_ptr);
}

+void __kvm_hyp_teardown(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.
- * Uses __kvm_call_hyp() to avoid kaslr's kvm_ksym_ref() translation.
- */
- __kvm_call_hyp((void *)kvm_hyp_reset_entry(),
- boot_pgd_ptr, phys_idmap_start);
+ kvm_call_hyp(__kvm_hyp_teardown, phys_idmap_start);
}

static inline void kvm_arch_hardware_unsetup(void) {}
diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index a873a6d..6b29d3d 100644
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -53,10 +53,9 @@ __invalid:
b .

/*
- * x0: HYP boot pgd
- * x1: HYP pgd
- * x2: HYP stack
- * x3: HYP vectors
+ * x0: HYP pgd
+ * x1: HYP stack
+ * x2: HYP vectors
*/
__do_hyp_init:

@@ -110,71 +109,27 @@ __do_hyp_init:
msr sctlr_el2, x4
isb

- /* Skip the trampoline dance if we merged the boot and runtime PGDs */
- cmp x0, x1
- b.eq merged
-
- /* MMU is now enabled. Get ready for the trampoline dance */
- ldr x4, =TRAMPOLINE_VA
- adr x5, target
- bfi x4, x5, #0, #PAGE_SHIFT
- br x4
-
-target: /* We're now in the trampoline code, switch page tables */
- msr ttbr0_el2, x1
- isb
-
- /* Invalidate the old TLBs */
- tlbi alle2
- dsb sy
-
-merged:
/* Set the stack and new vectors */
+ kern_hyp_va x1
+ mov sp, x1
kern_hyp_va x2
- mov sp, x2
- kern_hyp_va x3
- msr vbar_el2, x3
+ msr vbar_el2, x2

/* Hello, World! */
eret
ENDPROC(__kvm_hyp_init)

/*
- * Reset kvm back to the hyp stub. This is the trampoline dance in
- * reverse. If kvm used an extended idmap, __extended_idmap_trampoline
- * calls this code directly in the idmap. In this case switching to the
- * boot tables is a no-op.
- *
- * x0: HYP boot pgd
- * x1: HYP phys_idmap_start
+ * Reset kvm back to the hyp stub.
*/
ENTRY(__kvm_hyp_reset)
- /* 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 or stale code. */
- ic iallu
- tlbi alle2
- dsb sy
- isb
-
- /* 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
+ 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
diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
index 70254a6..ce9e5e5 100644
--- a/arch/arm64/kvm/hyp/entry.S
+++ b/arch/arm64/kvm/hyp/entry.S
@@ -164,22 +164,3 @@ alternative_endif

eret
ENDPROC(__fpsimd_guest_restore)
-
-/*
- * When using the extended idmap, we don't have a trampoline page we can use
- * while we switch pages tables during __kvm_hyp_reset. Accessing the idmap
- * directly would be ideal, but if we're using the extended idmap then the
- * idmap is located above HYP_PAGE_OFFSET, and the address will be masked by
- * kvm_call_hyp using kern_hyp_va.
- *
- * x0: HYP boot pgd
- * x1: HYP phys_idmap_start
- */
-ENTRY(__extended_idmap_trampoline)
- mov x4, x1
- adr_l x3, __kvm_hyp_reset
-
- /* insert __kvm_hyp_reset()s offset into phys_idmap_start */
- bfi x4, x3, #0, #PAGE_SHIFT
- br x4
-ENDPROC(__extended_idmap_trampoline)
diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
index 2d87f36..f6d9694 100644
--- a/arch/arm64/kvm/hyp/hyp-entry.S
+++ b/arch/arm64/kvm/hyp/hyp-entry.S
@@ -62,6 +62,21 @@ ENTRY(__vhe_hyp_call)
isb
ret
ENDPROC(__vhe_hyp_call)
+
+/*
+ * Compute the idmap address of __kvm_hyp_reset based on the idmap
+ * start passed as a parameter, and jump there.
+ *
+ * x0: HYP phys_idmap_start
+ */
+ENTRY(__kvm_hyp_teardown)
+ mov x4, x0
+ adr_l x3, __kvm_hyp_reset
+
+ /* insert __kvm_hyp_reset()s offset into phys_idmap_start */
+ bfi x4, x3, #0, #PAGE_SHIFT
+ br x4
+ENDPROC(__kvm_hyp_teardown)

el1_sync: // Guest trapped into EL2
save_x0_to_x3
diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index d044ca3..deee1b1 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -132,14 +132,3 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
/* Reset timer */
return kvm_timer_vcpu_reset(vcpu, cpu_vtimer_irq);
}
-
-unsigned long kvm_hyp_reset_entry(void)
-{
- /*
- * KVM is running with merged page tables, which don't have the
- * trampoline page mapped. We know the idmap is still mapped,
- * but can't be called into directly. Use
- * __extended_idmap_trampoline to do the call.
- */
- return (unsigned long)kvm_ksym_ref(__extended_idmap_trampoline);
-}
--
2.1.4