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Commit 3421e9d8 authored by Marc Zyngier's avatar Marc Zyngier Committed by Christoffer Dall
Browse files

arm64: KVM: Simplify HYP init/teardown 



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: default avatarMarc Zyngier <marc.zyngier@arm.com>
Signed-off-by: default avatarChristoffer Dall <christoffer.dall@linaro.org>
parent 0535a3e2

arch/arm64/include/asm/kvm_host.h

+3 −9
Original line number Diff line number Diff line
@@ -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) {}

arch/arm64/kvm/hyp-init.S

+8 −53
Original line number Diff line number Diff line
@@ -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

arch/arm64/kvm/hyp/entry.S

+0 −19
Original line number Diff line number Diff line
@@ -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)

arch/arm64/kvm/hyp/hyp-entry.S

+15 −0
Original line number Diff line number Diff line
@@ -63,6 +63,21 @@ ENTRY(__vhe_hyp_call) 
	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

arch/arm64/kvm/reset.c

+0 −11
Original line number Diff line number Diff line
@@ -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);

}