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Commit 27025a60 authored by Liu Ping Fan's avatar Liu Ping Fan Committed by Alexander Graf
Browse files

powerpc: kvm: optimize "sc 1" as fast return 



In some scene, e.g openstack CI, PR guest can trigger "sc 1" frequently,
this patch optimizes the path by directly delivering BOOK3S_INTERRUPT_SYSCALL
to HV guest, so powernv can return to HV guest without heavy exit, i.e,
no need to swap TLB, HTAB,.. etc

Signed-off-by: default avatarLiu Ping Fan <pingfank@linux.vnet.ibm.com>
Signed-off-by: default avatarAlexander Graf <agraf@suse.de>
parent 8a3caa6d

arch/powerpc/kvm/book3s_hv.c

+4 −6
Original line number Diff line number Diff line
@@ -669,12 +669,10 @@ static int kvmppc_handle_exit_hv(struct kvm_run *run, struct kvm_vcpu *vcpu, 
		/* hcall - punt to userspace */

		int i;



		if (vcpu->arch.shregs.msr & MSR_PR) {

			/* sc 1 from userspace - reflect to guest syscall */

			kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_SYSCALL);

			r = RESUME_GUEST;

			break;

		}

		/* hypercall with MSR_PR has already been handled in rmode,

		 * and never reaches here.

		 */



		run->papr_hcall.nr = kvmppc_get_gpr(vcpu, 3);

		for (i = 0; i < 9; ++i)

			run->papr_hcall.args[i] = kvmppc_get_gpr(vcpu, 4 + i);

arch/powerpc/kvm/book3s_hv_rmhandlers.S

+18 −1
Original line number Diff line number Diff line
@@ -686,6 +686,13 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_206) 
5:	mtspr	SPRN_SRR0, r6

	mtspr	SPRN_SRR1, r7



/*

 * Required state:

 * R4 = vcpu

 * R10: value for HSRR0

 * R11: value for HSRR1

 * R13 = PACA

 */

fast_guest_return:

	li	r0,0

	stb	r0,VCPU_CEDED(r4)	/* cancel cede */
@@ -1471,7 +1478,8 @@ kvmppc_hisi: 
hcall_try_real_mode:

	ld	r3,VCPU_GPR(R3)(r9)

	andi.	r0,r11,MSR_PR

	bne	guest_exit_cont

	/* sc 1 from userspace - reflect to guest syscall */

	bne	sc_1_fast_return

	clrrdi	r3,r3,2

	cmpldi	r3,hcall_real_table_end - hcall_real_table

	bge	guest_exit_cont
@@ -1492,6 +1500,15 @@ hcall_try_real_mode: 
	ld	r11,VCPU_MSR(r4)

	b	fast_guest_return



sc_1_fast_return:

	mtspr	SPRN_SRR0,r10

	mtspr	SPRN_SRR1,r11

	li	r10, BOOK3S_INTERRUPT_SYSCALL

	li	r11, (MSR_ME << 1) | 1  /* synthesize MSR_SF | MSR_ME */

	rotldi	r11, r11, 63

	mr	r4,r9

	b	fast_guest_return



	/* We've attempted a real mode hcall, but it's punted it back

	 * to userspace.  We need to restore some clobbered volatiles

	 * before resuming the pass-it-to-qemu path */