On Sat, Aug 15, 2015 at 08:27:04PM +1000, Alexey Kardashevskiy wrote:
>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"?).
>
Hmm... as the last sentence in previous paragraph said, 64MB VF BAR would
occupy a quarter of the 64bit-prefetchable window which is affordable.
Maybe I could change to this:
This patch replaces magic limit of 64MB with "gate", which is 1/4 of the
M64 Segment Size(m64_segsize >> 2) and adds comment to explain the reason
for it.
This time I use (m64_segsize >> 2) instead of (m64_segsize >> 1), since I
decide to still use ">" instead of ">=". By doing so, the explanation in
commit log is consistent with the code.
>
>>
>>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.
Good.
>
>
>> 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.
>
As you wish.
>
>>+ 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
--
Richard Yang
Help you, Help me
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