Commit 5236756d authored by Nicholas Piggin's avatar Nicholas Piggin Committed by Michael Ellerman
Browse files

KVM: PPC: Book3S HV P9: Use Linux SPR save/restore to manage some host SPRs 



Linux implements SPR save/restore including storage space for registers
in the task struct for process context switching. Make use of this
similarly to the way we make use of the context switching fp/vec save
restore.

This improves code reuse, allows some stack space to be saved, and helps
with avoiding VRSAVE updates if they are not required.

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/20211123095231.1036501-39-npiggin@gmail.com
parent 022ecb96

arch/powerpc/include/asm/switch_to.h

+1 −0
Original line number Diff line number Diff line
@@ -113,6 +113,7 @@ static inline void clear_task_ebb(struct task_struct *t) 
}



void kvmppc_save_user_regs(void);

void kvmppc_save_current_sprs(void);



extern int set_thread_tidr(struct task_struct *t);

arch/powerpc/kernel/process.c

+6 −0
Original line number Diff line number Diff line
@@ -1182,6 +1182,12 @@ void kvmppc_save_user_regs(void) 
#endif

}

EXPORT_SYMBOL_GPL(kvmppc_save_user_regs);



void kvmppc_save_current_sprs(void)

{

	save_sprs(&current->thread);

}

EXPORT_SYMBOL_GPL(kvmppc_save_current_sprs);

#endif /* CONFIG_KVM_BOOK3S_HV_POSSIBLE */



static inline void restore_sprs(struct thread_struct *old_thread,

arch/powerpc/kvm/book3s_hv.c

+1 −20
Original line number Diff line number Diff line
@@ -4566,9 +4566,6 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) 
	struct kvm_run *run = vcpu->run;

	int r;

	int srcu_idx;

	unsigned long ebb_regs[3] = {};	/* shut up GCC */

	unsigned long user_tar = 0;

	unsigned int user_vrsave;

	struct kvm *kvm;

	unsigned long msr;
@@ -4629,14 +4626,7 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) 


	kvmppc_save_user_regs();



	/* Save userspace EBB and other register values */

	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {

		ebb_regs[0] = mfspr(SPRN_EBBHR);

		ebb_regs[1] = mfspr(SPRN_EBBRR);

		ebb_regs[2] = mfspr(SPRN_BESCR);

		user_tar = mfspr(SPRN_TAR);

	}

	user_vrsave = mfspr(SPRN_VRSAVE);

	kvmppc_save_current_sprs();



	vcpu->arch.waitp = &vcpu->arch.vcore->wait;

	vcpu->arch.pgdir = kvm->mm->pgd;
@@ -4677,15 +4667,6 @@ static int kvmppc_vcpu_run_hv(struct kvm_vcpu *vcpu) 
		}

	} while (is_kvmppc_resume_guest(r));



	/* Restore userspace EBB and other register values */

	if (cpu_has_feature(CPU_FTR_ARCH_207S)) {

		mtspr(SPRN_EBBHR, ebb_regs[0]);

		mtspr(SPRN_EBBRR, ebb_regs[1]);

		mtspr(SPRN_BESCR, ebb_regs[2]);

		mtspr(SPRN_TAR, user_tar);

	}

	mtspr(SPRN_VRSAVE, user_vrsave);



	vcpu->arch.state = KVMPPC_VCPU_NOTREADY;

	atomic_dec(&kvm->arch.vcpus_running);

arch/powerpc/kvm/book3s_hv.h

+0 −3
Original line number Diff line number Diff line
@@ -4,11 +4,8 @@ 
 * Privileged (non-hypervisor) host registers to save.

 */

struct p9_host_os_sprs {

	unsigned long dscr;

	unsigned long tidr;

	unsigned long iamr;

	unsigned long amr;

	unsigned long fscr;



	unsigned int pmc1;

	unsigned int pmc2;

arch/powerpc/kvm/book3s_hv_p9_entry.c

+65 −28
Original line number Diff line number Diff line
@@ -231,15 +231,26 @@ EXPORT_SYMBOL_GPL(switch_pmu_to_host); 
static void load_spr_state(struct kvm_vcpu *vcpu,

				struct p9_host_os_sprs *host_os_sprs)

{

	/* TAR is very fast */

	mtspr(SPRN_TAR, vcpu->arch.tar);



#ifdef CONFIG_ALTIVEC

	if (cpu_has_feature(CPU_FTR_ALTIVEC) &&

	    current->thread.vrsave != vcpu->arch.vrsave)

		mtspr(SPRN_VRSAVE, vcpu->arch.vrsave);

#endif



	if (vcpu->arch.hfscr & HFSCR_EBB) {

		if (current->thread.ebbhr != vcpu->arch.ebbhr)

			mtspr(SPRN_EBBHR, vcpu->arch.ebbhr);

		if (current->thread.ebbrr != vcpu->arch.ebbrr)

			mtspr(SPRN_EBBRR, vcpu->arch.ebbrr);

		if (current->thread.bescr != vcpu->arch.bescr)

			mtspr(SPRN_BESCR, vcpu->arch.bescr);

	}



	if (cpu_has_feature(CPU_FTR_P9_TIDR))

	if (cpu_has_feature(CPU_FTR_P9_TIDR) &&

			current->thread.tidr != vcpu->arch.tid)

		mtspr(SPRN_TIDR, vcpu->arch.tid);

	if (host_os_sprs->iamr != vcpu->arch.iamr)

		mtspr(SPRN_IAMR, vcpu->arch.iamr);
@@ -247,9 +258,9 @@ static void load_spr_state(struct kvm_vcpu *vcpu, 
		mtspr(SPRN_AMR, vcpu->arch.amr);

	if (vcpu->arch.uamor != 0)

		mtspr(SPRN_UAMOR, vcpu->arch.uamor);

	if (host_os_sprs->fscr != vcpu->arch.fscr)

	if (current->thread.fscr != vcpu->arch.fscr)

		mtspr(SPRN_FSCR, vcpu->arch.fscr);

	if (host_os_sprs->dscr != vcpu->arch.dscr)

	if (current->thread.dscr != vcpu->arch.dscr)

		mtspr(SPRN_DSCR, vcpu->arch.dscr);

	if (vcpu->arch.pspb != 0)

		mtspr(SPRN_PSPB, vcpu->arch.pspb);
@@ -269,20 +280,15 @@ static void store_spr_state(struct kvm_vcpu *vcpu) 
{

	vcpu->arch.tar = mfspr(SPRN_TAR);



#ifdef CONFIG_ALTIVEC

	if (cpu_has_feature(CPU_FTR_ALTIVEC))

		vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);

#endif



	if (vcpu->arch.hfscr & HFSCR_EBB) {

		vcpu->arch.ebbhr = mfspr(SPRN_EBBHR);

		vcpu->arch.ebbrr = mfspr(SPRN_EBBRR);

		vcpu->arch.bescr = mfspr(SPRN_BESCR);

		/*

		 * This is like load_fp in context switching, turn off the

		 * facility after it wraps the u8 to try avoiding saving

		 * and restoring the registers each partition switch.

		 */

		if (!vcpu->arch.nested) {

			vcpu->arch.load_ebb++;

			if (!vcpu->arch.load_ebb)

				vcpu->arch.hfscr &= ~HFSCR_EBB;

		}

	}



	if (cpu_has_feature(CPU_FTR_P9_TIDR))
@@ -324,7 +330,6 @@ bool load_vcpu_state(struct kvm_vcpu *vcpu, 
#ifdef CONFIG_ALTIVEC

	load_vr_state(&vcpu->arch.vr);

#endif

	mtspr(SPRN_VRSAVE, vcpu->arch.vrsave);



	return ret;

}
@@ -338,7 +343,6 @@ void store_vcpu_state(struct kvm_vcpu *vcpu) 
#ifdef CONFIG_ALTIVEC

	store_vr_state(&vcpu->arch.vr);

#endif

	vcpu->arch.vrsave = mfspr(SPRN_VRSAVE);



#ifdef CONFIG_PPC_TRANSACTIONAL_MEM

	if (cpu_has_feature(CPU_FTR_TM) ||
@@ -364,12 +368,8 @@ EXPORT_SYMBOL_GPL(store_vcpu_state); 


void save_p9_host_os_sprs(struct p9_host_os_sprs *host_os_sprs)

{

	if (cpu_has_feature(CPU_FTR_P9_TIDR))

		host_os_sprs->tidr = mfspr(SPRN_TIDR);

	host_os_sprs->iamr = mfspr(SPRN_IAMR);

	host_os_sprs->amr = mfspr(SPRN_AMR);

	host_os_sprs->fscr = mfspr(SPRN_FSCR);

	host_os_sprs->dscr = mfspr(SPRN_DSCR);

}

EXPORT_SYMBOL_GPL(save_p9_host_os_sprs);
@@ -377,26 +377,63 @@ EXPORT_SYMBOL_GPL(save_p9_host_os_sprs); 
void restore_p9_host_os_sprs(struct kvm_vcpu *vcpu,

			     struct p9_host_os_sprs *host_os_sprs)

{

	/*

	 * current->thread.xxx registers must all be restored to host

	 * values before a potential context switch, othrewise the context

	 * switch itself will overwrite current->thread.xxx with the values

	 * from the guest SPRs.

	 */



	mtspr(SPRN_SPRG_VDSO_WRITE, local_paca->sprg_vdso);



	if (cpu_has_feature(CPU_FTR_P9_TIDR))

		mtspr(SPRN_TIDR, host_os_sprs->tidr);

	if (cpu_has_feature(CPU_FTR_P9_TIDR) &&

			current->thread.tidr != vcpu->arch.tid)

		mtspr(SPRN_TIDR, current->thread.tidr);

	if (host_os_sprs->iamr != vcpu->arch.iamr)

		mtspr(SPRN_IAMR, host_os_sprs->iamr);

	if (vcpu->arch.uamor != 0)

		mtspr(SPRN_UAMOR, 0);

	if (host_os_sprs->amr != vcpu->arch.amr)

		mtspr(SPRN_AMR, host_os_sprs->amr);

	if (host_os_sprs->fscr != vcpu->arch.fscr)

		mtspr(SPRN_FSCR, host_os_sprs->fscr);

	if (host_os_sprs->dscr != vcpu->arch.dscr)

		mtspr(SPRN_DSCR, host_os_sprs->dscr);

	if (current->thread.fscr != vcpu->arch.fscr)

		mtspr(SPRN_FSCR, current->thread.fscr);

	if (current->thread.dscr != vcpu->arch.dscr)

		mtspr(SPRN_DSCR, current->thread.dscr);

	if (vcpu->arch.pspb != 0)

		mtspr(SPRN_PSPB, 0);



	/* Save guest CTRL register, set runlatch to 1 */

	if (!(vcpu->arch.ctrl & 1))

		mtspr(SPRN_CTRLT, 1);



#ifdef CONFIG_ALTIVEC

	if (cpu_has_feature(CPU_FTR_ALTIVEC) &&

	    vcpu->arch.vrsave != current->thread.vrsave)

		mtspr(SPRN_VRSAVE, current->thread.vrsave);

#endif

	if (vcpu->arch.hfscr & HFSCR_EBB) {

		if (vcpu->arch.bescr != current->thread.bescr)

			mtspr(SPRN_BESCR, current->thread.bescr);

		if (vcpu->arch.ebbhr != current->thread.ebbhr)

			mtspr(SPRN_EBBHR, current->thread.ebbhr);

		if (vcpu->arch.ebbrr != current->thread.ebbrr)

			mtspr(SPRN_EBBRR, current->thread.ebbrr);



		if (!vcpu->arch.nested) {

			/*

			 * This is like load_fp in context switching, turn off

			 * the facility after it wraps the u8 to try avoiding

			 * saving and restoring the registers each partition

			 * switch.

			 */

			vcpu->arch.load_ebb++;

			if (!vcpu->arch.load_ebb)

				vcpu->arch.hfscr &= ~HFSCR_EBB;

		}

	}



	if (vcpu->arch.tar != current->thread.tar)

		mtspr(SPRN_TAR, current->thread.tar);

}

EXPORT_SYMBOL_GPL(restore_p9_host_os_sprs);