Re: [PATCH v2 20/30] KVM: s390: pci: provide routines for enabling/disabling IOAT assist

Pierre Morel <pmorel@xxxxxxxxxxxxx> · Tue, 25 Jan 2022 14:29:57 +0100

On 1/14/22 21:31, Matthew Rosato wrote:
These routines will be wired into the vfio_pci_zdev ioctl handlers to
respond to requests to enable / disable a device for PCI I/O Address
Translation assistance.

Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
  arch/s390/include/asm/kvm_pci.h |  15 ++++
  arch/s390/include/asm/pci_dma.h |   2 +
  arch/s390/kvm/pci.c             | 139 ++++++++++++++++++++++++++++++++
  arch/s390/kvm/pci.h             |   2 +
  4 files changed, 158 insertions(+)

diff --git a/arch/s390/include/asm/kvm_pci.h b/arch/s390/include/asm/kvm_pci.h
index 01fe14fffd7a..770849f13a70 100644
--- a/arch/s390/include/asm/kvm_pci.h
+++ b/arch/s390/include/asm/kvm_pci.h
@@ -16,11 +16,21 @@
  #include <linux/kvm_host.h>
  #include <linux/kvm.h>
  #include <linux/pci.h>
+#include <linux/mutex.h>
  #include <asm/pci_insn.h>
+#include <asm/pci_dma.h>
+
+struct kvm_zdev_ioat {
+	unsigned long *head[ZPCI_TABLE_PAGES];
+	unsigned long **seg;
+	unsigned long ***pt;
+	struct mutex lock;

Can we please rename the mutex ioat_lock to have a unique name easy to 
follow for maintenance.
Can you please add a description about when the lock should be used?

+};
  
  struct kvm_zdev {
  	struct zpci_dev *zdev;
  	struct kvm *kvm;
+	struct kvm_zdev_ioat ioat;
  	struct zpci_fib fib;
  };
  
@@ -33,6 +43,11 @@ int kvm_s390_pci_aif_enable(struct zpci_dev *zdev, struct zpci_fib *fib,
  			    bool assist);
  int kvm_s390_pci_aif_disable(struct zpci_dev *zdev);
  
+int kvm_s390_pci_ioat_probe(struct zpci_dev *zdev);
+int kvm_s390_pci_ioat_enable(struct zpci_dev *zdev, u64 iota);
+int kvm_s390_pci_ioat_disable(struct zpci_dev *zdev);
+u8 kvm_s390_pci_get_dtsm(struct zpci_dev *zdev);
+
  int kvm_s390_pci_interp_probe(struct zpci_dev *zdev);
  int kvm_s390_pci_interp_enable(struct zpci_dev *zdev);
  int kvm_s390_pci_interp_disable(struct zpci_dev *zdev);
diff --git a/arch/s390/include/asm/pci_dma.h b/arch/s390/include/asm/pci_dma.h
index 91e63426bdc5..69e616d0712c 100644
--- a/arch/s390/include/asm/pci_dma.h
+++ b/arch/s390/include/asm/pci_dma.h
@@ -50,6 +50,8 @@ enum zpci_ioat_dtype {
  #define ZPCI_TABLE_ALIGN		ZPCI_TABLE_SIZE
  #define ZPCI_TABLE_ENTRY_SIZE		(sizeof(unsigned long))
  #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_BITS			11
  #define ZPCI_PT_BITS			8
diff --git a/arch/s390/kvm/pci.c b/arch/s390/kvm/pci.c
index 7ed9abc476b6..39c13c25a700 100644
--- a/arch/s390/kvm/pci.c
+++ b/arch/s390/kvm/pci.c
@@ -13,12 +13,15 @@
  #include <asm/pci.h>
  #include <asm/pci_insn.h>
  #include <asm/pci_io.h>
+#include <asm/pci_dma.h>
  #include <asm/sclp.h>
  #include "pci.h"
  #include "kvm-s390.h"
  
  struct zpci_aift *aift;
  
+#define shadow_ioat_init zdev->kzdev->ioat.head[0]
+
  static inline int __set_irq_noiib(u16 ctl, u8 isc)
  {
  	union zpci_sic_iib iib = {{0}};
@@ -344,6 +347,135 @@ int kvm_s390_pci_aif_disable(struct zpci_dev *zdev)
  }
  EXPORT_SYMBOL_GPL(kvm_s390_pci_aif_disable);
  
+int kvm_s390_pci_ioat_probe(struct zpci_dev *zdev)
+{
+	/* Must have a KVM association registered */

may be add something like : "The ioat structure is embeded in kzdev"

+	if (!zdev->kzdev || !zdev->kzdev->kvm)

Why do we need to check for kvm ?
Having kzdev is already tested by the unique caller.

+		return -EINVAL;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_s390_pci_ioat_probe);
+
+int kvm_s390_pci_ioat_enable(struct zpci_dev *zdev, u64 iota)
+{
+	gpa_t gpa = (gpa_t)(iota & ZPCI_RTE_ADDR_MASK);
+	struct kvm_zdev_ioat *ioat;
+	struct page *page;
+	struct kvm *kvm;
+	unsigned int idx;
+	void *iaddr;
+	int i, rc = 0;

no need to initialize rc

+
+	if (shadow_ioat_init)
+		return -EINVAL;
+
+	/* Ensure supported type specified */
+	if ((iota & ZPCI_IOTA_RTTO_FLAG) != ZPCI_IOTA_RTTO_FLAG)
+		return -EINVAL;
+
+	kvm = zdev->kzdev->kvm;
+	ioat = &zdev->kzdev->ioat;
+	mutex_lock(&ioat->lock);
+	idx = srcu_read_lock(&kvm->srcu);
+	for (i = 0; i < ZPCI_TABLE_PAGES; i++) {
+		page = gfn_to_page(kvm, gpa_to_gfn(gpa));
+		if (is_error_page(page)) {
+			srcu_read_unlock(&kvm->srcu, idx);
+			rc = -EIO;
+			goto out;

			goto unpin ?

+		}
+		iaddr = page_to_virt(page) + (gpa & ~PAGE_MASK);
+		ioat->head[i] = (unsigned long *)iaddr;
+		gpa += PAGE_SIZE;
+	}
+	srcu_read_unlock(&kvm->srcu, idx);
+
+	zdev->kzdev->ioat.seg = kcalloc(ZPCI_TABLE_ENTRIES_PAGES,
+					sizeof(unsigned long *), GFP_KERNEL);

What about:

        ioat->seg = kcalloc(ZPCI_TABLE_ENTRIES_PAGES,
                            sizeof(*ioat->seg), GFP_KERNEL);
	if (!ioat->seg)
...
	ioat->pt = ...
?

+	if (!zdev->kzdev->ioat.seg)
+		goto unpin;
+	zdev->kzdev->ioat.pt = kcalloc(ZPCI_TABLE_ENTRIES,
+				       sizeof(unsigned long **), GFP_KERNEL);
+	if (!zdev->kzdev->ioat.pt)
+		goto free_seg;
+
+out:
+	mutex_unlock(&ioat->lock);
+	return rc;

	return 0 ?

+
+free_seg:
+	kfree(zdev->kzdev->ioat.seg);

kfree(ioat->seg) ?
rc = -ENOMEM;

+unpin:
+	for (i = 0; i < ZPCI_TABLE_PAGES; i++) {
+		kvm_release_pfn_dirty((u64)ioat->head[i] >> PAGE_SHIFT);
+		ioat->head[i] = 0;
+	}
+	mutex_unlock(&ioat->lock);
+	return -ENOMEM;

	return rc;

+}
...snip...

--
Pierre Morel
IBM Lab Boeblingen






