Subject: Re: [PATCH] powerpc/powernv: use one M64 BAR in Single PE mode for one VF BAR

From: Wei Yang <[email-masked]>
Date: Thu, 30 Jul 2015 13:43:59 +0800

On Thu, Jul 30, 2015 at 11:15:01AM +1000, Gavin Shan wrote:
>On Wed, Jul 29, 2015 at 03:22:07PM +0800, Wei Yang wrote:
>>In current implementation, when VF BAR is bigger than 64MB, it uses 4 M64
>>BAR in Single PE mode to cover the number of VFs required to be enabled.
>>By doing so, several VFs would be in one VF Group and leads to interference
>>between VFs in the same group.
>>
>>This patch changes the design by using one M64 BAR in Single PE mode for
>>one VF BAR. This gives absolute isolation for VFs.
>>
>>Signed-off-by: Wei Yang <[email-masked]>
>>---
>> arch/powerpc/include/asm/pci-bridge.h     |    5 +-
>> arch/powerpc/platforms/powernv/pci-ioda.c |  104 +++++------------------------
>> 2 files changed, 18 insertions(+), 91 deletions(-)
>>
>
>questions regarding this:
>
>(1) When M64 BAR is running in single-PE-mode for VFs, the alignment for one
>    particular IOV BAR still have to be (IOV_BAR_size * max_vf_number), or
>    M64 segment size of last BAR (0x10000000) is fine? If the later one is fine,
>    more M64 space would be saved. On the other hand, if the IOV BAR size
>    (for all VFs) is less than 256MB, will the allocated resource conflict
>    with the M64 segments in last BAR?

Not need to be IOV BAR size aligned, be individual VF BAR size aligned is fine.

IOV BAR size = VF BAR size * expended_num_vfs

>(2) When M64 BAR is in single-PE-mode, the PE numbers allocated for VFs need
>    continuous or not.

No, not need.

>(3) Each PF could have 6 IOV BARs and there're 15 available M64 BAR. It means
>    only two VFs can be enabled in the extreme case. Would it be a problem?
>

Yes, you are right.

Based on Alexey's mail, full isolation is more important than more VFs.

>>diff --git a/arch/powerpc/include/asm/pci-bridge.h b/arch/powerpc/include/asm/pci-bridge.h
>>index 712add5..1997e5d 100644
>>--- a/arch/powerpc/include/asm/pci-bridge.h
>>+++ b/arch/powerpc/include/asm/pci-bridge.h
>>@@ -214,10 +214,9 @@ struct pci_dn {
>> 	u16     vfs_expanded;		/* number of VFs IOV BAR expanded */
>> 	u16     num_vfs;		/* number of VFs enabled*/
>> 	int     offset;			/* PE# for the first VF PE */
>>-#define M64_PER_IOV 4
>>-	int     m64_per_iov;
>>+#define MAX_M64_WINDOW  16
>> #define IODA_INVALID_M64        (-1)
>>-	int     m64_wins[PCI_SRIOV_NUM_BARS][M64_PER_IOV];
>>+	int     m64_wins[PCI_SRIOV_NUM_BARS][MAX_M64_WINDOW];
>> #endif /* CONFIG_PCI_IOV */
>> #endif
>
>The "m64_wins" would be renamed to "m64_map". Also, it would have dynamic size:
>
>- When the IOV BAR is extended to 256 segments, its size is sizeof(int) * PCI_SRIOV_NUM_BARS;
>- When the IOV BAR is extended to max_vf_num, its size is sizeof(int) * max_vf_num;
>
>> 	struct list_head child_list;
>>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>index 5738d31..b3e7909 100644
>>--- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>@@ -1168,7 +1168,7 @@ static int pnv_pci_vf_release_m64(struct pci_dev *pdev)
>> 	pdn = pci_get_pdn(pdev);
>>
>> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++)
>>-		for (j = 0; j < M64_PER_IOV; j++) {
>>+		for (j = 0; j < MAX_M64_WINDOW; j++) {
>> 			if (pdn->m64_wins[i][j] == IODA_INVALID_M64)
>> 				continue;
>> 			opal_pci_phb_mmio_enable(phb->opal_id,
>>@@ -1193,8 +1193,7 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>> 	int                    total_vfs;
>> 	resource_size_t        size, start;
>> 	int                    pe_num;
>>-	int                    vf_groups;
>>-	int                    vf_per_group;
>>+	int                    m64s;
>
>"m64s" could have better name. For example, "vfs_per_m64_bar"...
>

m64s is used to represent number of M64 BARs necessary to enable num_vfs.
vfs_per_m64_bar may be misleading.

How about "m64_bars" ?

>>
>> 	bus = pdev->bus;
>> 	hose = pci_bus_to_host(bus);
>>@@ -1204,17 +1203,13 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>>
>> 	/* Initialize the m64_wins to IODA_INVALID_M64 */
>> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++)
>>-		for (j = 0; j < M64_PER_IOV; j++)
>>+		for (j = 0; j < MAX_M64_WINDOW; j++)
>> 			pdn->m64_wins[i][j] = IODA_INVALID_M64;
>>
>>-	if (pdn->m64_per_iov == M64_PER_IOV) {
>>-		vf_groups = (num_vfs <= M64_PER_IOV) ? num_vfs: M64_PER_IOV;
>>-		vf_per_group = (num_vfs <= M64_PER_IOV)? 1:
>>-			roundup_pow_of_two(num_vfs) / pdn->m64_per_iov;
>>-	} else {
>>-		vf_groups = 1;
>>-		vf_per_group = 1;
>>-	}
>>+	if (pdn->vfs_expanded != phb->ioda.total_pe)
>>+		m64s = num_vfs;
>>+	else
>>+		m64s = 1;
>
>The condition (pdn->vfs_expanded != phb->ioda.total_pe) isn't precise enough as
>explained below.
>
>>
>> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>> 		res = &pdev->resource[i + PCI_IOV_RESOURCES];
>>@@ -1224,7 +1219,7 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>> 		if (!pnv_pci_is_mem_pref_64(res->flags))
>> 			continue;
>>
>>-		for (j = 0; j < vf_groups; j++) {
>>+		for (j = 0; j < m64s; j++) {
>> 			do {
>> 				win = find_next_zero_bit(&phb->ioda.m64_bar_alloc,
>> 						phb->ioda.m64_bar_idx + 1, 0);
>>@@ -1235,10 +1230,9 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>>
>> 			pdn->m64_wins[i][j] = win;
>>
>>-			if (pdn->m64_per_iov == M64_PER_IOV) {
>>+			if (pdn->vfs_expanded != phb->ioda.total_pe) {
>> 				size = pci_iov_resource_size(pdev,
>> 							PCI_IOV_RESOURCES + i);
>>-				size = size * vf_per_group;
>> 				start = res->start + size * j;
>> 			} else {
>> 				size = resource_size(res);
>>@@ -1246,7 +1240,7 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>> 			}
>>
>> 			/* Map the M64 here */
>>-			if (pdn->m64_per_iov == M64_PER_IOV) {
>>+			if (pdn->vfs_expanded != phb->ioda.total_pe) {
>> 				pe_num = pdn->offset + j;
>> 				rc = opal_pci_map_pe_mmio_window(phb->opal_id,
>> 						pe_num, OPAL_M64_WINDOW_TYPE,
>>@@ -1267,7 +1261,7 @@ static int pnv_pci_vf_assign_m64(struct pci_dev *pdev, u16 num_vfs)
>> 				goto m64_failed;
>> 			}
>>
>>-			if (pdn->m64_per_iov == M64_PER_IOV)
>>+			if (pdn->vfs_expanded != phb->ioda.total_pe)
>> 				rc = opal_pci_phb_mmio_enable(phb->opal_id,
>> 				     OPAL_M64_WINDOW_TYPE, pdn->m64_wins[i][j], 2);
>> 			else
>>@@ -1311,15 +1305,13 @@ static void pnv_pci_ioda2_release_dma_pe(struct pci_dev *dev, struct pnv_ioda_pe
>> 	iommu_free_table(tbl, of_node_full_name(dev->dev.of_node));
>> }
>>
>>-static void pnv_ioda_release_vf_PE(struct pci_dev *pdev, u16 num_vfs)
>>+static void pnv_ioda_release_vf_PE(struct pci_dev *pdev)
>> {
>> 	struct pci_bus        *bus;
>> 	struct pci_controller *hose;
>> 	struct pnv_phb        *phb;
>> 	struct pnv_ioda_pe    *pe, *pe_n;
>> 	struct pci_dn         *pdn;
>>-	u16                    vf_index;
>>-	int64_t                rc;
>>
>> 	bus = pdev->bus;
>> 	hose = pci_bus_to_host(bus);
>>@@ -1329,35 +1321,6 @@ static void pnv_ioda_release_vf_PE(struct pci_dev *pdev, u16 num_vfs)
>> 	if (!pdev->is_physfn)
>> 		return;
>>
>>-	if (pdn->m64_per_iov == M64_PER_IOV && num_vfs > M64_PER_IOV) {
>>-		int   vf_group;
>>-		int   vf_per_group;
>>-		int   vf_index1;
>>-
>>-		vf_per_group = roundup_pow_of_two(num_vfs) / pdn->m64_per_iov;
>>-
>>-		for (vf_group = 0; vf_group < M64_PER_IOV; vf_group++)
>>-			for (vf_index = vf_group * vf_per_group;
>>-				vf_index < (vf_group + 1) * vf_per_group &&
>>-				vf_index < num_vfs;
>>-				vf_index++)
>>-				for (vf_index1 = vf_group * vf_per_group;
>>-					vf_index1 < (vf_group + 1) * vf_per_group &&
>>-					vf_index1 < num_vfs;
>>-					vf_index1++){
>>-
>>-					rc = opal_pci_set_peltv(phb->opal_id,
>>-						pdn->offset + vf_index,
>>-						pdn->offset + vf_index1,
>>-						OPAL_REMOVE_PE_FROM_DOMAIN);
>>-
>>-					if (rc)
>>-					    dev_warn(&pdev->dev, "%s: Failed to unlink same group PE#%d(%lld)\n",
>>-						__func__,
>>-						pdn->offset + vf_index1, rc);
>>-				}
>>-	}
>>-
>> 	list_for_each_entry_safe(pe, pe_n, &phb->ioda.pe_list, list) {
>> 		if (pe->parent_dev != pdev)
>> 			continue;
>>@@ -1392,10 +1355,10 @@ void pnv_pci_sriov_disable(struct pci_dev *pdev)
>> 	num_vfs = pdn->num_vfs;
>>
>> 	/* Release VF PEs */
>>-	pnv_ioda_release_vf_PE(pdev, num_vfs);
>>+	pnv_ioda_release_vf_PE(pdev);
>>
>> 	if (phb->type == PNV_PHB_IODA2) {
>>-		if (pdn->m64_per_iov == 1)
>>+		if (pdn->vfs_expanded == phb->ioda.total_pe)
>> 			pnv_pci_vf_resource_shift(pdev, -pdn->offset);
>>
>> 		/* Release M64 windows */
>>@@ -1418,7 +1381,6 @@ static void pnv_ioda_setup_vf_PE(struct pci_dev *pdev, u16 num_vfs)
>> 	int                    pe_num;
>> 	u16                    vf_index;
>> 	struct pci_dn         *pdn;
>>-	int64_t                rc;
>>
>> 	bus = pdev->bus;
>> 	hose = pci_bus_to_host(bus);
>>@@ -1463,37 +1425,6 @@ static void pnv_ioda_setup_vf_PE(struct pci_dev *pdev, u16 num_vfs)
>>
>> 		pnv_pci_ioda2_setup_dma_pe(phb, pe);
>> 	}
>>-
>>-	if (pdn->m64_per_iov == M64_PER_IOV && num_vfs > M64_PER_IOV) {
>>-		int   vf_group;
>>-		int   vf_per_group;
>>-		int   vf_index1;
>>-
>>-		vf_per_group = roundup_pow_of_two(num_vfs) / pdn->m64_per_iov;
>>-
>>-		for (vf_group = 0; vf_group < M64_PER_IOV; vf_group++) {
>>-			for (vf_index = vf_group * vf_per_group;
>>-			     vf_index < (vf_group + 1) * vf_per_group &&
>>-			     vf_index < num_vfs;
>>-			     vf_index++) {
>>-				for (vf_index1 = vf_group * vf_per_group;
>>-				     vf_index1 < (vf_group + 1) * vf_per_group &&
>>-				     vf_index1 < num_vfs;
>>-				     vf_index1++) {
>>-
>>-					rc = opal_pci_set_peltv(phb->opal_id,
>>-						pdn->offset + vf_index,
>>-						pdn->offset + vf_index1,
>>-						OPAL_ADD_PE_TO_DOMAIN);
>>-
>>-					if (rc)
>>-					    dev_warn(&pdev->dev, "%s: Failed to link same group PE#%d(%lld)\n",
>>-						__func__,
>>-						pdn->offset + vf_index1, rc);
>>-				}
>>-			}
>>-		}
>>-	}
>> }
>>
>> int pnv_pci_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
>>@@ -1537,7 +1468,7 @@ int pnv_pci_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
>> 		 * the IOV BAR according to the PE# allocated to the VFs.
>> 		 * Otherwise, the PE# for the VF will conflict with others.
>> 		 */
>>-		if (pdn->m64_per_iov == 1) {
>>+		if (pdn->vfs_expanded == phb->ioda.total_pe) {
>
>This condition isn't precise enough. When PF occasionally supports 256 VFs
>and the summed size of all IOV BARs (explained below) exceeds 64MB, we're
>expecting to use singole-pe-mode M64 BARs, not shared-mode.
>

Yes, you are right. The vfs_expanded is not reliable.

>> 			ret = pnv_pci_vf_resource_shift(pdev, pdn->offset);
>> 			if (ret)
>> 				goto m64_failed;
>>@@ -1570,8 +1501,7 @@ int pcibios_sriov_enable(struct pci_dev *pdev, u16 num_vfs)
>> 	/* Allocate PCI data */
>> 	add_dev_pci_data(pdev);
>>
>>-	pnv_pci_sriov_enable(pdev, num_vfs);
>>-	return 0;
>>+	return pnv_pci_sriov_enable(pdev, num_vfs);
>> }
>> #endif /* CONFIG_PCI_IOV */
>>
>>@@ -2766,7 +2696,6 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>> 	pdn->vfs_expanded = 0;
>>
>> 	total_vfs = pci_sriov_get_totalvfs(pdev);
>>-	pdn->m64_per_iov = 1;
>> 	mul = phb->ioda.total_pe;
>>
>> 	for (i = 0; i < PCI_SRIOV_NUM_BARS; i++) {
>>@@ -2785,7 +2714,6 @@ static void pnv_pci_ioda_fixup_iov_resources(struct pci_dev *pdev)
>> 		if (size > (1 << 26)) {
>
>Actually, the condition isn't precise enough. In theory, every PF can have 6 IOV BARs.
>If all of their size are 64MB, we will have 256 extended VFs. The total MMIO size needed
>is: 96GB = (6 * 64MB * 256), which exceeds 64GB. The original idea would be to have
>the scheme other than extending to 256 VFs when the sum of all IOV BARs is bigger
>than 64MB, not single M64 BAR. It's different issue and you can fix it up in another
>patch if you want.
>

I didn't get your point here.

You mean it is necessary to check the sum of IOV BAR instead of a single one?

>> 			dev_info(&pdev->dev, "PowerNV: VF BAR%d: %pR IOV size is bigger than 64M, roundup power2\n",
>> 				 i, res);
>>-			pdn->m64_per_iov = M64_PER_IOV;
>> 			mul = roundup_pow_of_two(total_vfs);
>> 			break;
>> 		}
>>-- 
>>1.7.9.5
>>

-- 
Richard Yang
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