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Commit f74a8e22 authored by James Hogan's avatar James Hogan Committed by Paolo Bonzini
Browse files

MIPS: KVM: Add count frequency KVM register 



Expose the KVM guest CP0_Count frequency to userland via a new
KVM_REG_MIPS_COUNT_HZ register accessible with the KVM_{GET,SET}_ONE_REG
ioctls.

When the frequency is altered the bias is adjusted such that the guest
CP0_Count doesn't jump discontinuously or lose any timer interrupts.

Signed-off-by: default avatarJames Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: kvm@vger.kernel.org
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: David Daney <david.daney@cavium.com>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f8239342

arch/mips/include/asm/kvm_host.h

+1 −0
Original line number Diff line number Diff line
@@ -720,6 +720,7 @@ void kvm_mips_write_compare(struct kvm_vcpu *vcpu, uint32_t compare); 
void kvm_mips_init_count(struct kvm_vcpu *vcpu);

int kvm_mips_set_count_ctl(struct kvm_vcpu *vcpu, s64 count_ctl);

int kvm_mips_set_count_resume(struct kvm_vcpu *vcpu, s64 count_resume);

int kvm_mips_set_count_hz(struct kvm_vcpu *vcpu, s64 count_hz);

void kvm_mips_count_enable_cause(struct kvm_vcpu *vcpu);

void kvm_mips_count_disable_cause(struct kvm_vcpu *vcpu);

enum hrtimer_restart kvm_mips_count_timeout(struct kvm_vcpu *vcpu);

arch/mips/include/uapi/asm/kvm.h

+7 −0
Original line number Diff line number Diff line
@@ -133,6 +133,13 @@ struct kvm_fpu { 
 */

#define KVM_REG_MIPS_COUNT_RESUME	(KVM_REG_MIPS | KVM_REG_SIZE_U64 | \

					 0x20000 | 1)

/*

 * CP0_Count rate in Hz

 * Specifies the rate of the CP0_Count timer in Hz. Modifications occur without

 * discontinuities in CP0_Count.

 */

#define KVM_REG_MIPS_COUNT_HZ		(KVM_REG_MIPS | KVM_REG_SIZE_U64 | \

					 0x20000 | 2)



/*

 * KVM MIPS specific structures and definitions

arch/mips/kvm/kvm_mips.c

+3 −0
Original line number Diff line number Diff line
@@ -546,6 +546,7 @@ static u64 kvm_mips_get_one_regs[] = { 


	KVM_REG_MIPS_COUNT_CTL,

	KVM_REG_MIPS_COUNT_RESUME,

	KVM_REG_MIPS_COUNT_HZ,

};



static int kvm_mips_get_reg(struct kvm_vcpu *vcpu,
@@ -627,6 +628,7 @@ static int kvm_mips_get_reg(struct kvm_vcpu *vcpu, 
	case KVM_REG_MIPS_CP0_COUNT:

	case KVM_REG_MIPS_COUNT_CTL:

	case KVM_REG_MIPS_COUNT_RESUME:

	case KVM_REG_MIPS_COUNT_HZ:

		ret = kvm_mips_callbacks->get_one_reg(vcpu, reg, &v);

		if (ret)

			return ret;
@@ -724,6 +726,7 @@ static int kvm_mips_set_reg(struct kvm_vcpu *vcpu, 
	case KVM_REG_MIPS_CP0_CAUSE:

	case KVM_REG_MIPS_COUNT_CTL:

	case KVM_REG_MIPS_COUNT_RESUME:

	case KVM_REG_MIPS_COUNT_HZ:

		return kvm_mips_callbacks->set_one_reg(vcpu, reg, v);

	default:

		return -EINVAL;

arch/mips/kvm/kvm_mips_emul.c

+48 −0
Original line number Diff line number Diff line
@@ -497,6 +497,54 @@ void kvm_mips_init_count(struct kvm_vcpu *vcpu) 
	kvm_mips_write_count(vcpu, 0);

}



/**

 * kvm_mips_set_count_hz() - Update the frequency of the timer.

 * @vcpu:	Virtual CPU.

 * @count_hz:	Frequency of CP0_Count timer in Hz.

 *

 * Change the frequency of the CP0_Count timer. This is done atomically so that

 * CP0_Count is continuous and no timer interrupt is lost.

 *

 * Returns:	-EINVAL if @count_hz is out of range.

 *		0 on success.

 */

int kvm_mips_set_count_hz(struct kvm_vcpu *vcpu, s64 count_hz)

{

	struct mips_coproc *cop0 = vcpu->arch.cop0;

	int dc;

	ktime_t now;

	u32 count;



	/* ensure the frequency is in a sensible range... */

	if (count_hz <= 0 || count_hz > NSEC_PER_SEC)

		return -EINVAL;

	/* ... and has actually changed */

	if (vcpu->arch.count_hz == count_hz)

		return 0;



	/* Safely freeze timer so we can keep it continuous */

	dc = kvm_mips_count_disabled(vcpu);

	if (dc) {

		now = kvm_mips_count_time(vcpu);

		count = kvm_read_c0_guest_count(cop0);

	} else {

		now = kvm_mips_freeze_hrtimer(vcpu, &count);

	}



	/* Update the frequency */

	vcpu->arch.count_hz = count_hz;

	vcpu->arch.count_period = div_u64((u64)NSEC_PER_SEC << 32, count_hz);

	vcpu->arch.count_dyn_bias = 0;



	/* Calculate adjusted bias so dynamic count is unchanged */

	vcpu->arch.count_bias = count - kvm_mips_ktime_to_count(vcpu, now);



	/* Update and resume hrtimer */

	if (!dc)

		kvm_mips_resume_hrtimer(vcpu, now, count);

	return 0;

}



/**

 * kvm_mips_write_compare() - Modify compare and update timer.

 * @vcpu:	Virtual CPU.

arch/mips/kvm/kvm_trap_emul.c

+6 −0
Original line number Diff line number Diff line
@@ -415,6 +415,9 @@ static int kvm_trap_emul_get_one_reg(struct kvm_vcpu *vcpu, 
	case KVM_REG_MIPS_COUNT_RESUME:

		*v = ktime_to_ns(vcpu->arch.count_resume);

		break;

	case KVM_REG_MIPS_COUNT_HZ:

		*v = vcpu->arch.count_hz;

		break;

	default:

		return -EINVAL;

	}
@@ -461,6 +464,9 @@ static int kvm_trap_emul_set_one_reg(struct kvm_vcpu *vcpu, 
	case KVM_REG_MIPS_COUNT_RESUME:

		ret = kvm_mips_set_count_resume(vcpu, v);

		break;

	case KVM_REG_MIPS_COUNT_HZ:

		ret = kvm_mips_set_count_hz(vcpu, v);

		break;

	default:

		return -EINVAL;

	}