Subject: Re: [PATCH V4 5/6] powerpc/powernv: boundary the total VF BAR size instead of the individual one

From: Wei Yang <[email-masked]>
Date: Thu, 8 Oct 2015 15:13:11 +0800

On Fri, Oct 02, 2015 at 07:51:17PM +1000, Alexey Kardashevskiy wrote:
>On 08/19/2015 12:01 PM, Wei Yang wrote:
>>Each VF could have 6 BARs at most. When the total BAR size exceeds the
>>gate, after expanding it will also exhaust the M64 Window.
>>
>>This patch limits the boundary by checking the total VF BAR size instead of
>>the individual BAR.
>
>The gate is the biggest segment size in PE in shared mode, right? And this is
>64MB. Also, BARs with the same number of all VFs of the same physical adapter
>will be mapper contiguously (as one huge IOV BAR), for example, 2 VFs, 2 BARs
>each, mapping will look like:
>VF0-BAR0, VF1-BAR0, VF0-BAR1, VF1-BAR1
>but not like this:
>VF0-BAR0, VF0-BAR1, VF1-BAR0, VF1-BAR1
>Is this correct?
>

Yes, your understanding is correct. It will look like:

VF0-BAR0, VF1-BAR0, VF0-BAR1, VF1-BAR1

>
>
>>
>>Signed-off-by: Wei Yang <[email-masked]>
>>Reviewed-by: Gavin Shan <[email-masked]>
>>---
>>  arch/powerpc/platforms/powernv/pci-ioda.c |   14 ++++++++------
>>  1 file changed, 8 insertions(+), 6 deletions(-)
>>
>>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>index b8bc51f..4bc83b8 100644
>>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>@@ -2701,7 +2701,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>>  	const resource_size_t gate = phb->ioda.m64_segsize >> 2;
>>  	struct resource *res;
>>  	int i;
>>-	resource_size_t size;
>>+	resource_size_t size, total_vf_bar_sz;
>>  	struct pci_dn *pdn;
>>  	int mul, total_vfs;
>>
>>@@ -2714,6 +2714,7 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>>
>>  	total_vfs = pci_sriov_get_totalvfs(pdev);
>>  	mul = phb->ioda.total_pe;
>>+	total_vf_bar_sz = 0;
>>
>>  	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>>  		res = &pdev->resource[i + PCI_IOV_RESOURCES];
>>@@ -2726,7 +2727,8 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>>  			return;
>>  		}
>>
>>-		size = pci_iov_resource_size(pdev, i + PCI_IOV_RESOURCES);
>>+		total_vf_bar_sz += pci_iov_resource_size(pdev,
>>+				i + PCI_IOV_RESOURCES);
>
>
>Is @pdev a physical device in this context? I assume it is so
>pci_iov_resource_size() returns the entire IOV BAR size.
>For example, I have a Mellanox card with 16 VFs, each has a single 32MB BAR
>so total_vf_bar_sz will be 16*32=512MB and this will exceed the @gate size
>and we end up having m64_single_mode = true. What do I miss here?
>

@pdev is a PF here.

But pci_iov_resource_size() return VF BAR size instead of the entire IOV BAR
size.

The iov->barsz[] is set in sriov_init(). You could take a look at it.

>
>>
>>  		/*
>>  		 * If bigger than quarter of M64 segment size, just round up
>>@@ -2740,11 +2742,11 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>>  		 * limit the system flexibility.  This is a design decision to
>>  		 * set the boundary to quarter of the M64 segment size.
>>  		 */
>>-		if (size > gate) {
>>-			dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size "
>>-				"is bigger than %lld, roundup power2\n",
>>-				 i, res, gate);
>>+		if (total_vf_bar_sz > gate) {
>>  			mul = roundup_pow_of_two(total_vfs);
>>+			dev_info(&pdev->dev,
>>+				"VF BAR Total IOV size %llx > %llx, roundup to %d VFs\n",
>>+				total_vf_bar_sz, gate, mul);
>>  			pdn->m64_single_mode = true;
>>  			break;
>>  		}
>>
>
>
>-- 
>Alexey

-- 
Richard Yang
Help you, Help me