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MIPS: KVM: Add count frequency KVM register

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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: James 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: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
James Hogan 2014-05-29 10:16:38 +01:00 committed by Paolo Bonzini
parent f82393426a
commit f74a8e224e
5 changed files with 65 additions and 0 deletions
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1
arch/mips/include/asm/kvm_host.h
View file

@ -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);

7
arch/mips/include/uapi/asm/kvm.h
View file

@ -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

3
arch/mips/kvm/kvm_mips.c
View file

@ -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;

48
arch/mips/kvm/kvm_mips_emul.c
View file

@ -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.

6
arch/mips/kvm/kvm_trap_emul.c
View file

@ -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;
}