Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 97c4cfbe authored by Alexander Graf's avatar Alexander Graf Committed by Marcelo Tosatti
Browse files

KVM: PPC: Enable lightweight exits again 



The PowerPC C ABI defines that registers r14-r31 need to be preserved across
function calls. Since our exit handler is written in C, we can make use of that
and don't need to reload r14-r31 on every entry/exit cycle.

This technique is also used in the BookE code and is called "lightweight exits"
there. To follow the tradition, it's called the same in Book3S.

So far this optimization was disabled though, as the code didn't do what it was
expected to do, but failed to work.

This patch fixes and enables lightweight exits again.

Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
Signed-off-by: default avatarMarcelo Tosatti <mtosatti@redhat.com>
parent b480f780

arch/powerpc/kvm/book3s.c

+1 −3
Original line number Diff line number Diff line
@@ -539,8 +539,6 @@ int kvmppc_handle_pagefault(struct kvm_run *run, struct kvm_vcpu *vcpu, 
		r = kvmppc_emulate_mmio(run, vcpu);

		if ( r == RESUME_HOST_NV )

			r = RESUME_HOST;

		if ( r == RESUME_GUEST_NV )

			r = RESUME_GUEST;

	}



	return r;
@@ -645,7 +643,7 @@ int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu, 
		er = kvmppc_emulate_instruction(run, vcpu);

		switch (er) {

		case EMULATE_DONE:

			r = RESUME_GUEST;

			r = RESUME_GUEST_NV;

			break;

		case EMULATE_FAIL:

			printk(KERN_CRIT "%s: emulation at %lx failed (%08x)\n",

arch/powerpc/kvm/book3s_64_interrupts.S

+56 −50
Original line number Diff line number Diff line
@@ -40,6 +40,26 @@ 
       mtmsrd  r0,1

.endm



#define VCPU_LOAD_NVGPRS(vcpu) \

	ld	r14, VCPU_GPR(r14)(vcpu); \

	ld	r15, VCPU_GPR(r15)(vcpu); \

	ld	r16, VCPU_GPR(r16)(vcpu); \

	ld	r17, VCPU_GPR(r17)(vcpu); \

	ld	r18, VCPU_GPR(r18)(vcpu); \

	ld	r19, VCPU_GPR(r19)(vcpu); \

	ld	r20, VCPU_GPR(r20)(vcpu); \

	ld	r21, VCPU_GPR(r21)(vcpu); \

	ld	r22, VCPU_GPR(r22)(vcpu); \

	ld	r23, VCPU_GPR(r23)(vcpu); \

	ld	r24, VCPU_GPR(r24)(vcpu); \

	ld	r25, VCPU_GPR(r25)(vcpu); \

	ld	r26, VCPU_GPR(r26)(vcpu); \

	ld	r27, VCPU_GPR(r27)(vcpu); \

	ld	r28, VCPU_GPR(r28)(vcpu); \

	ld	r29, VCPU_GPR(r29)(vcpu); \

	ld	r30, VCPU_GPR(r30)(vcpu); \

	ld	r31, VCPU_GPR(r31)(vcpu); \



/*****************************************************************************

 *                                                                           *

 *     Guest entry / exit code that is in kernel module memory (highmem)     *
@@ -67,12 +87,16 @@ kvm_start_entry: 
	SAVE_NVGPRS(r1)



	/* Save LR */

	mflr	r14

	std	r14, _LINK(r1)

	std	r0, _LINK(r1)



	/* Load non-volatile guest state from the vcpu */

	VCPU_LOAD_NVGPRS(r4)



/* XXX optimize non-volatile loading away */

kvm_start_lightweight:



	ld	r9, VCPU_PC(r4)			/* r9 = vcpu->arch.pc */

	ld	r10, VCPU_SHADOW_MSR(r4)	/* r10 = vcpu->arch.shadow_msr */



	DISABLE_INTERRUPTS



	/* Save R1/R2 in the PACA */
@@ -81,29 +105,6 @@ kvm_start_lightweight: 
	ld	r3, VCPU_HIGHMEM_HANDLER(r4)

	std	r3, PACASAVEDMSR(r13)



	/* Load non-volatile guest state from the vcpu */

	ld	r14, VCPU_GPR(r14)(r4)

	ld	r15, VCPU_GPR(r15)(r4)

	ld	r16, VCPU_GPR(r16)(r4)

	ld	r17, VCPU_GPR(r17)(r4)

	ld	r18, VCPU_GPR(r18)(r4)

	ld	r19, VCPU_GPR(r19)(r4)

	ld	r20, VCPU_GPR(r20)(r4)

	ld	r21, VCPU_GPR(r21)(r4)

	ld	r22, VCPU_GPR(r22)(r4)

	ld	r23, VCPU_GPR(r23)(r4)

	ld	r24, VCPU_GPR(r24)(r4)

	ld	r25, VCPU_GPR(r25)(r4)

	ld	r26, VCPU_GPR(r26)(r4)

	ld	r27, VCPU_GPR(r27)(r4)

	ld	r28, VCPU_GPR(r28)(r4)

	ld	r29, VCPU_GPR(r29)(r4)

	ld	r30, VCPU_GPR(r30)(r4)

	ld	r31, VCPU_GPR(r31)(r4)



	ld	r9, VCPU_PC(r4)			/* r9 = vcpu->arch.pc */

	ld	r10, VCPU_SHADOW_MSR(r4)	/* r10 = vcpu->arch.shadow_msr */



	ld	r3, VCPU_TRAMPOLINE_ENTER(r4)

	mtsrr0	r3
@@ -247,7 +248,6 @@ kvmppc_handler_highmem: 


no_dcbz32_off:



	/* XXX maybe skip on lightweight? */

	std	r14, VCPU_GPR(r14)(r12)

	std	r15, VCPU_GPR(r15)(r12)

	std	r16, VCPU_GPR(r16)(r12)
@@ -267,9 +267,6 @@ no_dcbz32_off: 
	std	r30, VCPU_GPR(r30)(r12)

	std	r31, VCPU_GPR(r31)(r12)



	/* Restore non-volatile host registers (r14 - r31) */

	REST_NVGPRS(r1)



	/* Save guest PC (R10) */

	std	r10, VCPU_PC(r12)
@@ -351,42 +348,51 @@ kvm_return_point: 


	/* Jump back to lightweight entry if we're supposed to */

	/* go back into the guest */



	/* Pass the exit number as 3rd argument to kvmppc_handle_exit */

	mr	r5, r3



	/* Restore r3 (kvm_run) and r4 (vcpu) */

	REST_2GPRS(3, r1)

	bl	KVMPPC_HANDLE_EXIT



#if 0 /* XXX get lightweight exits back */

	/* If RESUME_GUEST, get back in the loop */

	cmpwi	r3, RESUME_GUEST

	bne	kvm_exit_heavyweight

	beq	kvm_loop_lightweight



	/* put VCPU and KVM_RUN back into place and roll again! */

	REST_2GPRS(3, r1)

	b	kvm_start_lightweight

	cmpwi	r3, RESUME_GUEST_NV

	beq	kvm_loop_heavyweight



kvm_exit_heavyweight:

	/* Restore non-volatile host registers */

	ld	r14, _LINK(r1)

	mtlr	r14

	REST_NVGPRS(r1)

kvm_exit_loop:



	addi    r1, r1, SWITCH_FRAME_SIZE

#else

	ld	r4, _LINK(r1)

	mtlr	r4



	cmpwi	r3, RESUME_GUEST

	bne	kvm_exit_heavyweight

	/* Restore non-volatile host registers (r14 - r31) */

	REST_NVGPRS(r1)



	addi    r1, r1, SWITCH_FRAME_SIZE

	blr



kvm_loop_heavyweight:



	ld	r4, _LINK(r1)

	std     r4, (16 + SWITCH_FRAME_SIZE)(r1)



	/* Load vcpu and cpu_run */

	REST_2GPRS(3, r1)



	addi    r1, r1, SWITCH_FRAME_SIZE

	/* Load non-volatile guest state from the vcpu */

	VCPU_LOAD_NVGPRS(r4)



	b	kvm_start_entry

	/* Jump back into the beginning of this function */

	b	kvm_start_lightweight



kvm_exit_heavyweight:

kvm_loop_lightweight:



	addi    r1, r1, SWITCH_FRAME_SIZE

#endif

	/* We'll need the vcpu pointer */

	REST_GPR(4, r1)



	/* Jump back into the beginning of this function */

	b	kvm_start_lightweight

	blr