Re: [PATCH RFC 2/6] KVM: s390: provide only a single function for setting the tod

"Collin L. Walling" <walling@xxxxxxxxxxxxxxxxxx> · Wed, 7 Feb 2018 15:13:23 -0500

On 02/07/2018 06:46 AM, David Hildenbrand wrote:
Right now, SET CLOCK called in the guest does not properly take care of
the epoch index, as the call goes via the old kvm_s390_set_tod_clock()
interface. So the epoch index is neither reset to 0, if required, nor
properly set to e.g. 0xff on negative values.

Fix this by providing a single kvm_s390_set_tod_clock() function. Move
Multiple-epoch facility handling into it.

Signed-off-by: David Hildenbrand<david@xxxxxxxxxx>
---
  arch/s390/kvm/kvm-s390.c | 46 +++++++++++++++-------------------------------
  arch/s390/kvm/kvm-s390.h |  5 ++---
  arch/s390/kvm/priv.c     |  9 +++++----
  3 files changed, 22 insertions(+), 38 deletions(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ba4c7092335a..b514ee427077 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -902,12 +902,9 @@ static int kvm_s390_set_tod_ext(struct kvm *kvm, struct kvm_device_attr *attr)
  	if (copy_from_user(&gtod, (void __user *)attr->addr, sizeof(gtod)))
  		return -EFAULT;

-	if (test_kvm_facility(kvm, 139))
-		kvm_s390_set_tod_clock_ext(kvm, &gtod);
-	else if (gtod.epoch_idx == 0)
-		kvm_s390_set_tod_clock(kvm, gtod.tod);
-	else
+	if (!test_kvm_facility(kvm, 139) && gtod.epoch_idx)
  		return -EINVAL;
+	kvm_s390_set_tod_clock(kvm, &gtod);

  	VM_EVENT(kvm, 3, "SET: TOD extension: 0x%x, TOD base: 0x%llx",
  		gtod.epoch_idx, gtod.tod);
@@ -932,13 +929,14 @@ static int kvm_s390_set_tod_high(struct kvm *kvm, struct kvm_device_attr *attr)

  static int kvm_s390_set_tod_low(struct kvm *kvm, struct kvm_device_attr *attr)
  {
-	u64 gtod;
+	struct kvm_s390_vm_tod_clock gtod = { 0 };

-	if (copy_from_user(&gtod, (void __user *)attr->addr, sizeof(gtod)))
+	if (copy_from_user(&gtod.tod, (void __user *)attr->addr,
+			   sizeof(gtod.tod)))
  		return -EFAULT;

-	kvm_s390_set_tod_clock(kvm, gtod);
-	VM_EVENT(kvm, 3, "SET: TOD base: 0x%llx", gtod);
+	kvm_s390_set_tod_clock(kvm, &gtod);
+	VM_EVENT(kvm, 3, "SET: TOD base: 0x%llx", gtod.tod);
  	return 0;
  }

@@ -3021,8 +3019,8 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
  	return 0;
  }

-void kvm_s390_set_tod_clock_ext(struct kvm *kvm,
-				 const struct kvm_s390_vm_tod_clock *gtod)
+void kvm_s390_set_tod_clock(struct kvm *kvm,
+			    const struct kvm_s390_vm_tod_clock *gtod)
Nit: off by one space --------^

  {
  	struct kvm_vcpu *vcpu;
  	struct kvm_s390_tod_clock_ext htod;
@@ -3034,10 +3032,12 @@ void kvm_s390_set_tod_clock_ext(struct kvm *kvm,
  	get_tod_clock_ext((char *)&htod);

  	kvm->arch.epoch = gtod->tod - htod.tod;
-	kvm->arch.epdx = gtod->epoch_idx - htod.epoch_idx;
-
-	if (kvm->arch.epoch > gtod->tod)
-		kvm->arch.epdx -= 1;
+	kvm->arch.epdx = 0;
+	if (test_kvm_facility(kvm, 139)) {
+		kvm->arch.epdx = gtod->epoch_idx - htod.epoch_idx;
+		if (kvm->arch.epoch > gtod->tod)
+			kvm->arch.epdx -= 1;
+	}

  	kvm_s390_vcpu_block_all(kvm);
  	kvm_for_each_vcpu(i, vcpu, kvm) {
@@ -3050,22 +3050,6 @@ void kvm_s390_set_tod_clock_ext(struct kvm *kvm,
  	mutex_unlock(&kvm->lock);
  }

-void kvm_s390_set_tod_clock(struct kvm *kvm, u64 tod)
-{
-	struct kvm_vcpu *vcpu;
-	int i;
-
-	mutex_lock(&kvm->lock);
-	preempt_disable();
-	kvm->arch.epoch = tod - get_tod_clock();
-	kvm_s390_vcpu_block_all(kvm);
-	kvm_for_each_vcpu(i, vcpu, kvm)
-		vcpu->arch.sie_block->epoch = kvm->arch.epoch;
-	kvm_s390_vcpu_unblock_all(kvm);
-	preempt_enable();
-	mutex_unlock(&kvm->lock);
-}
-
  /**
   * kvm_arch_fault_in_page - fault-in guest page if necessary
   * @vcpu: The corresponding virtual cpu
diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
index bd31b37b0e6f..19d719262765 100644
--- a/arch/s390/kvm/kvm-s390.h
+++ b/arch/s390/kvm/kvm-s390.h
@@ -283,9 +283,8 @@ int kvm_s390_handle_sigp(struct kvm_vcpu *vcpu);
  int kvm_s390_handle_sigp_pei(struct kvm_vcpu *vcpu);

  /* implemented in kvm-s390.c */
-void kvm_s390_set_tod_clock_ext(struct kvm *kvm,
-				 const struct kvm_s390_vm_tod_clock *gtod);
-void kvm_s390_set_tod_clock(struct kvm *kvm, u64 tod);
+void kvm_s390_set_tod_clock(struct kvm *kvm,
+			    const struct kvm_s390_vm_tod_clock *gtod);
Same nit here.
  long kvm_arch_fault_in_page(struct kvm_vcpu *vcpu, gpa_t gpa, int writable);
  int kvm_s390_store_status_unloaded(struct kvm_vcpu *vcpu, unsigned long addr);
  int kvm_s390_vcpu_store_status(struct kvm_vcpu *vcpu, unsigned long addr);
diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
index c4c4e157c036..33505c32c48a 100644
--- a/arch/s390/kvm/priv.c
+++ b/arch/s390/kvm/priv.c
@@ -85,9 +85,10 @@ int kvm_s390_handle_e3(struct kvm_vcpu *vcpu)
  /* Handle SCK (SET CLOCK) interception */
  static int handle_set_clock(struct kvm_vcpu *vcpu)
  {
+	struct kvm_s390_vm_tod_clock gtod = { 0 };
  	int rc;
  	u8 ar;
-	u64 op2, val;
+	u64 op2;

  	vcpu->stat.instruction_sck++;

@@ -97,12 +98,12 @@ static int handle_set_clock(struct kvm_vcpu *vcpu)
  	op2 = kvm_s390_get_base_disp_s(vcpu, &ar);
  	if (op2 & 7)	/* Operand must be on a doubleword boundary */
  		return kvm_s390_inject_program_int(vcpu, PGM_SPECIFICATION);
-	rc = read_guest(vcpu, op2, ar, &val, sizeof(val));
+	rc = read_guest(vcpu, op2, ar, &gtod.tod, sizeof(gtod.tod));
  	if (rc)
  		return kvm_s390_inject_prog_cond(vcpu, rc);

-	VCPU_EVENT(vcpu, 3, "SCK: setting guest TOD to 0x%llx", val);
-	kvm_s390_set_tod_clock(vcpu->kvm, val);
+	VCPU_EVENT(vcpu, 3, "SCK: setting guest TOD to 0x%llx", gtod.tod);
+	kvm_s390_set_tod_clock(vcpu->kvm, &gtod);

  	kvm_s390_set_psw_cc(vcpu, 0);
  	return 0;
Set clock only concerns the left-most 64 bits of the TOD-Clock, right? 
(thinking out
loud) I wonder if we need to also concern ourselves about the epoch 
extension... but
perhaps current use cases of set clock do not warrant that?

--
- Collin L Walling







