Commit 9c5a432a authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

KVM: PPC: Book3S HV P9: Remove subcore HMI handling 



On POWER9 and newer, rather than the complex HMI synchronisation and
subcore state, have each thread un-apply the guest TB offset before
calling into the early HMI handler.

This allows the subcore state to be avoided, including subcore enter
/ exit guest, which includes an expensive divide that shows up
slightly in profiles.

Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20211123095231.1036501-54-npiggin@gmail.com
parent 6398326b

arch/powerpc/include/asm/kvm_ppc.h

+1 −0
Original line number Diff line number Diff line
@@ -759,6 +759,7 @@ void kvmppc_realmode_machine_check(struct kvm_vcpu *vcpu); 
void kvmppc_subcore_enter_guest(void);

void kvmppc_subcore_exit_guest(void);

long kvmppc_realmode_hmi_handler(void);

long kvmppc_p9_realmode_hmi_handler(struct kvm_vcpu *vcpu);

long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,

                    long pte_index, unsigned long pteh, unsigned long ptel);

long kvmppc_h_remove(struct kvm_vcpu *vcpu, unsigned long flags,

arch/powerpc/kvm/book3s_hv.c

+5 −7
Original line number Diff line number Diff line
@@ -4033,8 +4033,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, 


	vcpu->arch.ceded = 0;



	kvmppc_subcore_enter_guest();



	vcpu_vpa_increment_dispatch(vcpu);



	if (kvmhv_on_pseries()) {
@@ -4087,8 +4085,6 @@ static int kvmhv_p9_guest_entry(struct kvm_vcpu *vcpu, u64 time_limit, 


	vcpu_vpa_increment_dispatch(vcpu);



	kvmppc_subcore_exit_guest();



	return trap;

}
@@ -6102,9 +6098,11 @@ static int kvmppc_book3s_init_hv(void) 
	if (r)

		return r;



	if (!cpu_has_feature(CPU_FTR_ARCH_300)) {

		r = kvm_init_subcore_bitmap();

		if (r)

			return r;

	}



	/*

	 * We need a way of accessing the XICS interrupt controller,

arch/powerpc/kvm/book3s_hv_hmi.c

+6 −1
Original line number Diff line number Diff line
@@ -20,10 +20,15 @@ void wait_for_subcore_guest_exit(void) 


	/*

	 * NULL bitmap pointer indicates that KVM module hasn't

	 * been loaded yet and hence no guests are running.

	 * been loaded yet and hence no guests are running, or running

	 * on POWER9 or newer CPU.

	 *

	 * If no KVM is in use, no need to co-ordinate among threads

	 * as all of them will always be in host and no one is going

	 * to modify TB other than the opal hmi handler.

	 *

	 * POWER9 and newer don't need this synchronisation.

	 *

	 * Hence, just return from here.

	 */

	if (!local_paca->sibling_subcore_state)

arch/powerpc/kvm/book3s_hv_p9_entry.c

+1 −1
Original line number Diff line number Diff line
@@ -1013,7 +1013,7 @@ int kvmhv_vcpu_entry_p9(struct kvm_vcpu *vcpu, u64 time_limit, unsigned long lpc 
		kvmppc_realmode_machine_check(vcpu);



	} else if (unlikely(trap == BOOK3S_INTERRUPT_HMI)) {

		kvmppc_realmode_hmi_handler();

		kvmppc_p9_realmode_hmi_handler(vcpu);



	} else if (trap == BOOK3S_INTERRUPT_H_EMUL_ASSIST) {

		vcpu->arch.emul_inst = mfspr(SPRN_HEIR);

arch/powerpc/kvm/book3s_hv_ras.c

+54 −0
Original line number Diff line number Diff line
@@ -136,6 +136,60 @@ void kvmppc_realmode_machine_check(struct kvm_vcpu *vcpu) 
	vcpu->arch.mce_evt = mce_evt;

}





long kvmppc_p9_realmode_hmi_handler(struct kvm_vcpu *vcpu)

{

	struct kvmppc_vcore *vc = vcpu->arch.vcore;

	long ret = 0;



	/*

	 * Unapply and clear the offset first. That way, if the TB was not

	 * resynced then it will remain in host-offset, and if it was resynced

	 * then it is brought into host-offset. Then the tb offset is

	 * re-applied before continuing with the KVM exit.

	 *

	 * This way, we don't need to actually know whether not OPAL resynced

	 * the timebase or do any of the complicated dance that the P7/8

	 * path requires.

	 */

	if (vc->tb_offset_applied) {

		u64 new_tb = mftb() - vc->tb_offset_applied;

		mtspr(SPRN_TBU40, new_tb);

		if ((mftb() & 0xffffff) < (new_tb & 0xffffff)) {

			new_tb += 0x1000000;

			mtspr(SPRN_TBU40, new_tb);

		}

		vc->tb_offset_applied = 0;

	}



	local_paca->hmi_irqs++;



	if (hmi_handle_debugtrig(NULL) >= 0) {

		ret = 1;

		goto out;

	}



	if (ppc_md.hmi_exception_early)

		ppc_md.hmi_exception_early(NULL);



out:

	if (vc->tb_offset) {

		u64 new_tb = mftb() + vc->tb_offset;

		mtspr(SPRN_TBU40, new_tb);

		if ((mftb() & 0xffffff) < (new_tb & 0xffffff)) {

			new_tb += 0x1000000;

			mtspr(SPRN_TBU40, new_tb);

		}

		vc->tb_offset_applied = vc->tb_offset;

	}



	return ret;

}



/*

 * The following subcore HMI handling is all only for pre-POWER9 CPUs.

 */



/* Check if dynamic split is in force and return subcore size accordingly. */

static inline int kvmppc_cur_subcore_size(void)

{