On 08/14/2015 12:11 AM, Wei Yang wrote:
At the moment 64bit-prefetchable window can be maximum 64GB, which is
currently got from device tree. This means that in shared mode the maximum
supported VF BAR size is 64GB/256=256MB. While this size could exhaust the
whole 64bit-prefetchable window. This is a design decision to set a
boundary to 64MB of the VF BAR size. Since VF BAR size with 64MB would
occupy a quarter of the 64bit-prefetchable window, this is affordable.
This patch replaces magic limit of 64MB with (m64_segsize >> 1) and adds
comment to explain the reason for it.
Having m64_segsize divided in _halves_ is also magic (or is it a "design
decision"?).
Signed-off-by: Wei Yang <weiy...@linux.vnet.ibm.com>
---
arch/powerpc/platforms/powernv/pci-ioda.c | 22 +++++++++++++++++-----
1 file changed, 17 insertions(+), 5 deletions(-)
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c
b/arch/powerpc/platforms/powernv/pci-ioda.c
index 4da0f50..3e8c0b4 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -2688,7 +2688,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct
pci_dev *pdev)
struct pnv_phb *phb;
struct resource *res;
int i;
- resource_size_t size;
+ resource_size_t size, gate;
It should be:
const resource_size_t gate = phb->ioda.m64_segsize >> 1;
as it never changes in the function.
struct pci_dn *pdn;
int mul, total_vfs;
@@ -2704,6 +2704,17 @@ static void pnv_pci_ioda_fixup_iov_resources(struct
pci_dev *pdev)
total_vfs = pci_sriov_get_totalvfs(pdev);
mul = phb->ioda.total_pe;
+ /*
+ * If bigger than or equal to half of M64 segment size, just round up
+ * power of two.
+ *
+ * Generally, one M64 BAR maps one IOV BAR. To avoid conflict with
+ * other devices, IOV BAR size is expanded to be (total_pe *
+ * VF_BAR_size). When VF_BAR_size is half of M64 segment size , the
+ * expanded size would equal to half of the whole M64 Space size,
+ * which will exhaust the M64 Space and limit the system flexibility.
+ */
+ gate = phb->ioda.m64_segsize >> 1;
for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
res = &pdev->resource[i + PCI_IOV_RESOURCES];
@@ -2718,10 +2729,11 @@ static void pnv_pci_ioda_fixup_iov_resources(struct
pci_dev *pdev)
size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
- /* bigger than 64M */
- if (size > (1 << 26)) {
- dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size is
bigger than 64M, roundup power2\n",
- i, res);
+ /* bigger than or equal to gate */
That multiline comment is better to be here, I think.
+ if (size >= gate) {
+ dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size "
+ "is bigger than %lld, roundup power2\n",
+ i, res, gate);
mul = roundup_pow_of_two(total_vfs);
pdn->m64_single_mode = true;
break;
--
Alexey
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