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@xxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Gleb Natapov <gleb@xxxxxxxxxx>
Cc: kvm@xxxxxxxxxxxxxxx
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: David Daney <david.daney@xxxxxxxxxx>
Cc: Sanjay Lal <sanjayl@xxxxxxxxxxx>
---
arch/mips/include/asm/kvm_host.h | 1 +
arch/mips/include/uapi/asm/kvm.h | 7 ++++++
arch/mips/kvm/kvm_mips.c | 3 +++
arch/mips/kvm/kvm_mips_emul.c | 48 ++++++++++++++++++++++++++++++++++++++++
arch/mips/kvm/kvm_trap_emul.c | 6 +++++
5 files changed, 65 insertions(+)
diff --git a/arch/mips/include/asm/kvm_host.h b/arch/mips/include/asm/kvm_host.h
index 1deeaecbe73e..f9c672f729ea 100644
--- a/arch/mips/include/asm/kvm_host.h
+++ b/arch/mips/include/asm/kvm_host.h
@@ -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);
diff --git a/arch/mips/include/uapi/asm/kvm.h b/arch/mips/include/uapi/asm/kvm.h
index f859fbada1f7..2c04b6d9ff85 100644
--- a/arch/mips/include/uapi/asm/kvm.h
+++ b/arch/mips/include/uapi/asm/kvm.h
@@ -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
diff --git a/arch/mips/kvm/kvm_mips.c b/arch/mips/kvm/kvm_mips.c
index 216ecaf2c18a..1472b0b3d93b 100644
--- a/arch/mips/kvm/kvm_mips.c
+++ b/arch/mips/kvm/kvm_mips.c
@@ -551,6 +551,7 @@ 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,
@@ -632,6 +633,7 @@ 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;
@@ -729,6 +731,7 @@ 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;
diff --git a/arch/mips/kvm/kvm_mips_emul.c b/arch/mips/kvm/kvm_mips_emul.c
index 65c8dea6d1f5..6d257384c9b4 100644
--- a/arch/mips/kvm/kvm_mips_emul.c
+++ b/arch/mips/kvm/kvm_mips_emul.c
@@ -498,6 +498,54 @@ void kvm_mips_init_count(struct kvm_vcpu *vcpu)
}
/**
+ * 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.
* @compare: New CP0_Compare value.
diff --git a/arch/mips/kvm/kvm_trap_emul.c b/arch/mips/kvm/kvm_trap_emul.c
index 854502bcc749..b171db324cf0 100644
--- a/arch/mips/kvm/kvm_trap_emul.c
+++ b/arch/mips/kvm/kvm_trap_emul.c
@@ -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;
}
--
1.9.3
