Subject: Re: [PATCH V2 1/6] powerpc/powernv: don't enable SRIOV when VF BAR contains non M64 BAR

From: Wei Yang <[email-masked]>
Date: Thu, 6 Aug 2015 22:10:10 +0800

On Thu, Aug 06, 2015 at 02:35:57PM +1000, Gavin Shan wrote:
>On Wed, Aug 05, 2015 at 09:24:58AM +0800, Wei Yang wrote:
>>On PHB_IODA2, we enable SRIOV devices by mapping IOV BAR with M64 BARs. If
>>a SRIOV device's BAR is not 64-bit prefetchable, this is not assigned from
>>M64 windwo, which means M64 BAR can't work on it.
>>
>
>s/PHB_IODA2/PHB3
>s/windwo/window
>
>>This patch makes this explicit.
>>
>>Signed-off-by: Wei Yang <[email-masked]>
>
>The idea sounds right, but there is one question as below.
>
>>---
>> arch/powerpc/platforms/powernv/pci-ioda.c |   25 +++++++++----------------
>> 1 file changed, 9 insertions(+), 16 deletions(-)
>>
>>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>index 5738d31..9b41dba 100644
>>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>@@ -908,9 +908,6 @@ static int pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
>> 		if (!res->flags || !res->parent)
>> 			continue;
>>
>>-		if (!pnv_pci_is_mem_pref_64(res->flags))
>>-			continue;
>>-
>> 		/*
>> 		 * The actual IOV BAR range is determined by the start address
>> 		 * and the actual size for num_vfs VFs BAR.  This check is to
>>@@ -939,9 +936,6 @@ static int pnv_pci_vf_resource_shift(struct pci_dev *dev, int offset)
>> 		if (!res->flags || !res->parent)
>> 			continue;
>>
>>-		if (!pnv_pci_is_mem_pref_64(res->flags))
>>-			continue;
>>-
>> 		size = pci_iov_resource_size(dev, i + PCI_IOV_RESOURCES);
>> 		res2 = *res;
>> 		res->start += size * offset;
>>@@ -1221,9 +1215,6 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>> 		if (!res->flags || !res->parent)
>> 			continue;
>>
>>-		if (!pnv_pci_is_mem_pref_64(res->flags))
>>-			continue;
>>-
>> 		for (j = 0; j < vf_groups; j++) {
>> 			do {
>> 				win = find_next_zero_bit(&phb->ioda.m64_bar_alloc,
>>@@ -1510,6 +1501,12 @@ int pnv_pci_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
>> 	pdn = pci_get_pdn(pdev);
>>
>> 	if (phb->type == PNV_PHB_IODA2) {
>>+		if (!pdn->vfs_expanded) {
>>+			dev_info(&pdev->dev, "don't support this SRIOV device"
>>+				" with non M64 VF BAR\n");
>>+			return -EBUSY;
>>+		}
>>+
>
>It would be -ENOSPC since -EBUSY indicates the devices (VFs) are temparily
>unavailable. For this case, the VFs are permanently unavailable because of
>running out of space to accomodate M64 and non-M64 VF BARs.
>
>The error message could be printed with dev_warn() and it would be precise
>as below or something else you prefer:
>
>	dev_warn(&pdev->dev, "SRIOV not supported because of non-M64 VF BAR\n");
>

Thanks for the comment, will change accordingly.

>
>> 		/* Calculate available PE for required VFs */
>> 		mutex_lock(&phb->ioda.pe_alloc_mutex);
>> 		pdn->offset = bitmap_find_next_zero_area(
>>@@ -2774,9 +2771,10 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>> 		if (!res->flags || res->parent)
>> 			continue;
>> 		if (!pnv_pci_is_mem_pref_64(res->flags)) {
>>-			dev_warn(&pdev->dev, " non M64 VF BAR%d: %pR\n",
>>+			dev_warn(&pdev->dev, "Don't support SR-IOV with"
>>+					" non M64 VF BAR%d: %pR. \n",
>> 				 i, res);
>>-			continue;
>>+			return;
>> 		}
>>
>> 		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>>@@ -2795,11 +2793,6 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>> 		res = &pdev->resource[i + PCI_IOV_RESOURCES];
>> 		if (!res->flags || res->parent)
>> 			continue;
>>-		if (!pnv_pci_is_mem_pref_64(res->flags)) {
>>-			dev_warn(&pdev->dev, "Skipping expanding VF BAR%d: %pR\n",
>>-				 i, res);
>>-			continue;
>>-		}
>
>When any one IOV BAR on the PF is non-M64, none of the VFs can be enabled.
>Will we still allocate/assign M64 or M32 resources for the IOV BARs? If so,
>I think it can be avoided.
>

Don't get your point. You mean to avoid this function?

Or clear the IOV BAR when we found one of it is non-M64?

>>
>> 		dev_dbg(&pdev->dev, " Fixing VF BAR%d: %pR to\n", i, res);
>> 		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>>-- 
>>1.7.9.5
>>

-- 
Richard Yang
Help you, Help me