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Re: [Xen-devel] [RFC v1 07/15] vt-d: Add API to update IRTE when VT-d PI is used



On 25/03/15 12:31, Feng Wu wrote:
This patch adds an API which is used to update the IRTE
for posted-interrupt when guest changes MSI/MSI-X information.

Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
---
  xen/drivers/passthrough/vtd/intremap.c | 83 ++++++++++++++++++++++++++++++++++
  xen/drivers/passthrough/vtd/iommu.h    |  3 ++
  xen/include/asm-x86/iommu.h            |  2 +
  3 files changed, 88 insertions(+)

diff --git a/xen/drivers/passthrough/vtd/intremap.c 
b/xen/drivers/passthrough/vtd/intremap.c
index 0333686..f44e74d 100644
--- a/xen/drivers/passthrough/vtd/intremap.c
+++ b/xen/drivers/passthrough/vtd/intremap.c
@@ -898,3 +898,86 @@ void iommu_disable_x2apic_IR(void)
      for_each_drhd_unit ( drhd )
          disable_qinval(drhd->iommu);
  }
+
+/*
+ * This function is used to update the IRTE for posted-interrupt
+ * when guest changes MSI/MSI-X information
+ */
+int pi_update_irte(struct vcpu *v, struct pirq *pirq, uint32_t gvec )

Stray space after gvec.

I presume gvec means "guest vector", in which case it should be a uint8_t.

+{
+    struct irq_desc *desc;
+    struct msi_desc *msi_desc;
+    int remap_index, rc = -1;
+    struct pci_dev *pci_dev;
+    struct acpi_drhd_unit *drhd;
+    struct iommu *iommu;
+    struct ir_ctrl *ir_ctrl;
+    struct iremap_entry *iremap_entries = NULL, *p = NULL;
+    struct iremap_entry new_ire;
+    struct pi_desc *pi_desc = &v->arch.hvm_vmx.pi_desc;
+    unsigned long flags;
+
+    desc = pirq_spin_lock_irq_desc(pirq, NULL);
+    if ( !desc )
+        return -1;
+
+    msi_desc = desc->msi_desc;
+    if ( !msi_desc )
+        goto unlock_out;
+
+    remap_index = msi_desc->remap_index;
+    pci_dev = msi_desc->dev;
+    if ( !pci_dev )
+        goto unlock_out;
+
+    drhd = acpi_find_matched_drhd_unit(pci_dev);

This does an O(n^2) walk over the dhrd_units list and the unit device_cnt. As the layout will be completely static, might it be better to stash drhd information in struct pci_dev during boot?

+    if (!drhd)

Spaces inside brackets.

+    {
+        dprintk(XENLOG_INFO VTDPREFIX, "failed to get drhd!\n");

This is a useless error message, providing no useful information to identify the issue.

At the very least it should identify the domain and vcpu (%pv of v), the guest vector and pci device. Also, drop the exclamation mark - it is not useful in the log.

+        goto unlock_out;
+    }
+
+    iommu = drhd->iommu;
+    ir_ctrl = iommu_ir_ctrl(iommu);
+    if ( !ir_ctrl )
+    {
+        dprintk(XENLOG_INFO VTDPREFIX, "failed to get ir_ctrl!\n");

Needs simiarly extending with some information.

+        goto unlock_out;
+    }
+
+    spin_lock_irqsave(&ir_ctrl->iremap_lock, flags);
+
+    GET_IREMAP_ENTRY(ir_ctrl->iremap_maddr, remap_index, iremap_entries, p);
+
+    memcpy(&new_ire, p, sizeof(struct iremap_entry));

sizeof(new_ire) please

+
+    /* Setup/Update interrupt remapping table entry */
+    new_ire.lo_intpost.urg = 0;
+    new_ire.lo_intpost.vector = gvec;
+    new_ire.lo_intpost.pda_l = (((u64)virt_to_maddr(pi_desc)) >>
+                                (32 - PDA_LOW_BIT)) & ~(-1UL << PDA_LOW_BIT);
+    new_ire.hi_intpost.pda_h = (((u64)virt_to_maddr(pi_desc)) >>  32) &
+                                ~(-1UL << PDA_HIGH_BIT);

Is it possible to hide this bit manipulation in side a static inline function which takes an ire and pi_desc pointer rather than open coding it?

+
+    new_ire.lo_intpost.res_1 = 0;
+    new_ire.lo_intpost.res_2 = 0;
+    new_ire.lo_intpost.res_3 = 0;
+    new_ire.hi_intpost.res_1 = 0;
+
+    new_ire.lo_intpost.im = 1;
+
+    memcpy(p, &new_ire, sizeof(struct iremap_entry));
+    iommu_flush_cache_entry(p, sizeof(struct iremap_entry));

Same here regarding sizeof.

Furthermore, is the memcpy() safe to update the live descriptor?

If it is, why do you not update the descriptor in place using p-> rather than copying it to the stack and back?

~Andrew

+    iommu_flush_iec_index(iommu, 0, remap_index);
+
+    if ( iremap_entries )
+        unmap_vtd_domain_page(iremap_entries);
+
+    spin_unlock_irqrestore(&ir_ctrl->iremap_lock, flags);
+
+    rc = 0;
+ unlock_out:
+    spin_unlock_irq(&desc->lock);
+
+    return rc;
+}
diff --git a/xen/drivers/passthrough/vtd/iommu.h 
b/xen/drivers/passthrough/vtd/iommu.h
index cd61e12..ffa72c8 100644
--- a/xen/drivers/passthrough/vtd/iommu.h
+++ b/xen/drivers/passthrough/vtd/iommu.h
@@ -334,6 +334,9 @@ struct iremap_entry {
    };
  };
+#define PDA_LOW_BIT 26
+#define PDA_HIGH_BIT   32
+
  /* Max intr remapping table page order is 8, as max number of IRTEs is 64K */
  #define IREMAP_PAGE_ORDER  8
diff --git a/xen/include/asm-x86/iommu.h b/xen/include/asm-x86/iommu.h
index e7a65da..d233621 100644
--- a/xen/include/asm-x86/iommu.h
+++ b/xen/include/asm-x86/iommu.h
@@ -32,6 +32,8 @@ int iommu_supports_eim(void);
  int iommu_enable_x2apic_IR(void);
  void iommu_disable_x2apic_IR(void);
+int pi_update_irte(struct vcpu *v, struct pirq *pirq, uint32_t gvec);
+
  #endif /* !__ARCH_X86_IOMMU_H__ */
  /*
   * Local variables:


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