Subject: Re: [PATCH V5 1/6] powerpc/powernv: don't enable SRIOV when VF BAR has non 64bit-prefetchable BAR

From: Gavin Shan <[email-masked]>
Date: Tue, 13 Oct 2015 14:20:30 +1100

On Tue, Oct 13, 2015 at 09:49:30AM +0800, Wei Yang wrote:
>On Tue, Oct 13, 2015 at 11:01:24AM +1100, Gavin Shan wrote:
>>On Fri, Oct 09, 2015 at 10:46:51AM +0800, Wei Yang wrote:
>>>On PHB_IODA2, we enable SRIOV devices by mapping IOV BAR with M64 BARs. If
>>>a SRIOV device's IOV BAR is not 64bit-prefetchable, this is not assigned
>>>from 64bit prefetchable window, which means M64 BAR can't work on it.
>>>
>>>The reason is PCI bridges support only 2 windows and the kernel code
>>>programs bridges in the way that one window is 32bit-nonprefetchable and
>>>the other one is 64bit-prefetchable. So if devices' IOV BAR is 64bit and
>>>non-prefetchable, it will be mapped into 32bit space and therefore M64
>>>cannot be used for it.
>>>
>>>This patch makes this explicit.
>>>
>>>Signed-off-by: Wei Yang <[email-masked]>
>>>Reviewed-by: Gavin Shan <[email-masked]>
>>>Acked-by: Alexey Kardashevskiy <[email-masked]>
>>>---
>>> 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 85cbc96..8c031b5 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 64bit-prefetchable IOV BAR\n");
>>>+			return -ENOSPC;
>>>+		}
>>>+
>>> 		/* Calculate available PE for required VFs */
>>> 		mutex_lock(&phb->ioda.pe_alloc_mutex);
>>> 		pdn->offset = bitmap_find_next_zero_area(
>>>@@ -2775,9 +2772,10 @@ 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;
>>
>>When the IOV BAR isn't 64-bits prefetchable one, it's going to be allocated from
>>M32 aperatus. However, the IOV BAR won't be used as the SRIOV capability on the PF
>>can't be enabled. Occasionally, the IOV BAR is huge (e.g. 4GB) and it eats up all
>>M32 space, BARs other than 64-bits prefetchable BARs on other device will fail in
>>this case. Would it a problem you ever thought of?
>>
>
>IOV BARs are in optional list during assignment.
>

The point isn't that optional list allows to be failed when assigning the resources.
The point is the system allocating resources without using them. Isn't it wasting
resources?

>>> 		}
>>>
>>> 		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>>>@@ -2796,11 +2794,6 @@ 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;
>>>-		}
>>>
>>> 		dev_dbg(&pdev->dev, " Fixing VF BAR%d: %pR to\n", i, res);
>>> 		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>>>-- 
>>>2.5.0
>>>
>
>-- 
>Richard Yang
>Help you, Help me