Re: [PATCH 23/32] KVM: s390: pci: handle refresh of PCI translations

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On 12/7/21 21:57, Matthew Rosato wrote:
Add a routine that will perform a shadow operation between a guest
and host IOAT.  A subsequent patch will invoke this in response to
an 04 RPCIT instruction intercept.

Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
  arch/s390/include/asm/kvm_pci.h |   1 +
  arch/s390/include/asm/pci_dma.h |   1 +
  arch/s390/kvm/pci.c             | 191 ++++++++++++++++++++++++++++++++
  arch/s390/kvm/pci.h             |   4 +-
  4 files changed, 196 insertions(+), 1 deletion(-)

diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
index 254275399f21..97e3a369135d 100644
--- a/arch/s390/include/asm/kvm_pci.h
+++ b/arch/s390/include/asm/kvm_pci.h
@@ -30,6 +30,7 @@ struct kvm_zdev_ioat {
  struct kvm_zdev {
  	struct zpci_dev *zdev;
  	struct kvm *kvm;
+	u64 rpcit_count;
  	struct kvm_zdev_ioat ioat;
  	struct zpci_fib fib;
  };
diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
index e1d3c1d3fc8a..0ca15e5db3d9 100644
--- a/arch/s390/include/asm/pci_dma.h
+++ b/arch/s390/include/asm/pci_dma.h
@@ -52,6 +52,7 @@ enum zpci_ioat_dtype {
  #define ZPCI_TABLE_ENTRIES		(ZPCI_TABLE_SIZE / ZPCI_TABLE_ENTRY_SIZE)
  #define ZPCI_TABLE_PAGES		(ZPCI_TABLE_SIZE >> PAGE_SHIFT)
  #define ZPCI_TABLE_ENTRIES_PAGES	(ZPCI_TABLE_ENTRIES * ZPCI_TABLE_PAGES)
+#define ZPCI_TABLE_ENTRIES_PER_PAGE	(ZPCI_TABLE_ENTRIES / ZPCI_TABLE_PAGES)
#define ZPCI_TABLE_BITS 11
  #define ZPCI_PT_BITS			8
diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index a1c0c0881332..858c5ecdc8b9 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -123,6 +123,195 @@ int kvm_s390_pci_aen_init(u8 nisc)
  	return rc;
  }

...snip...

+
+int kvm_s390_pci_refresh_trans(struct kvm_vcpu *vcpu, unsigned long req,
+			       unsigned long start, unsigned long size)
+{
+	struct zpci_dev *zdev;
+	u32 fh;
+	int rc;
+
+	/* If the device has a SHM bit on, let userspace take care of this */
+	fh = req >> 32;
+	if ((fh & aift.mdd) != 0)
+		return -EOPNOTSUPP;

I think you should make this check in the caller.

+
+	/* Make sure this is a valid device associated with this guest */
+	zdev = get_zdev_by_fh(fh);
+	if (!zdev || !zdev->kzdev || zdev->kzdev->kvm != vcpu->kvm)
+		return -EINVAL;
+
+	/* Only proceed if the device is using the assist */
+	if (zdev->kzdev->ioat.head[0] == 0)
+		return -EOPNOTSUPP;

Using the assist means using interpretation over using interception and legacy vfio-pci. right?

+
+	rc = dma_table_shadow(vcpu, zdev, start, size);
+	if (rc > 0)
+		rc = zpci_refresh_trans((u64) zdev->fh << 32, start, size);

Here you lose the status reported by the hardware.
You should directly use __rpcit(fn, addr, range, &status);


+	zdev->kzdev->rpcit_count++;
+
+	return rc;
+}
+
  /* Modify PCI: Register floating adapter interruption forwarding */
  static int kvm_zpci_set_airq(struct zpci_dev *zdev)
  {
@@ -590,4 +779,6 @@ void kvm_s390_pci_init(void)
  {
  	spin_lock_init(&aift.gait_lock);
  	mutex_init(&aift.lock);
+
+	WARN_ON(zpci_get_mdd(&aift.mdd));
  }
diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
index 3c86888fe1b3..d252a631b693 100644
--- a/arch/s390/kvm/pci.h
+++ b/arch/s390/kvm/pci.h
@@ -33,6 +33,7 @@ struct zpci_aift {
  	struct kvm_zdev **kzdev;
  	spinlock_t gait_lock; /* Protects the gait, used during AEN forward */
  	struct mutex lock; /* Protects the other structures in aift */
+	u32 mdd;
  };
static inline struct kvm *kvm_s390_pci_si_to_kvm(struct zpci_aift *aift,
@@ -47,7 +48,8 @@ struct zpci_aift *kvm_s390_pci_get_aift(void);
int kvm_s390_pci_aen_init(u8 nisc);
  void kvm_s390_pci_aen_exit(void);
-
+int kvm_s390_pci_refresh_trans(struct kvm_vcpu *vcpu, unsigned long req,
+			       unsigned long start, unsigned long end);
  void kvm_s390_pci_init(void);
#endif /* __KVM_S390_PCI_H */


--
Pierre Morel
IBM Lab Boeblingen



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