linux-kernel - Re: [PATCH v2] iov: restore NumVFs register to 0 before return from virtfn_max

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Date:	Thu, 15 Oct 2015 12:16:00 -0500
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Ethan Zhao <ethan.zhao@...cle.com>
Cc:	bhelgaas@...gle.com, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iov: restore NumVFs register to 0 before return from
 virtfn_max_buses()

Hi Ethan,

On Wed, Sep 16, 2015 at 12:19:53PM +0900, Ethan Zhao wrote:
> After commit 4449f079722c ("PCI: Calculate maximum number of buses
> required for VFs"),the initial value of NumVFs register was left to
> non-zero after sriov_init() and no VFs was enabled in device driver.
> this changed the behaviour of kernel exported by lspci and sysfs etc.
> so this patch restore the NumVFs register to zero after the
> calculation of max_VF_buses was done and before return from
> virtfn_max_buses().
> 
> Tested on stable 4.1 and passed building on stable 4.3-rc1
> 
> Signed-off-by: Ethan Zhao <ethan.zhao@...cle.com>
> Tested-by: Sriharsha Yadagudde <sriharsha.devdas@...cle.com>

Can you test the patch below?  I'm trying to avoid touching
PCI_SRIOV_NUM_VF in more than one place, and I think it's OK to set it
and test offset/stride at the end, instead of setting NUM_VF to zero,
testing offset/stride, computing max_bus, then setting NUM_VF to zero
again.

Bjorn


commit 8e20e89658f23b8d16b1e21810e9f63c8625129c
Author: Bjorn Helgaas <bhelgaas@...gle.com>
Date:   Thu Oct 15 11:31:21 2015 -0500

    PCI: Set SR-IOV NumVFs to zero after enumeration
    
    The enumeration path should leave NumVFs set to zero.  But after
    4449f079722c ("PCI: Calculate maximum number of buses required for VFs"),
    we call virtfn_max_buses() in the enumeration path, which changes NumVFs.
    This NumVFs change is visible via lspci and sysfs until a driver enables
    SR-IOV.
    
    Set NumVFs to zero after virtfn_max_buses() computes the maximum number of
    buses.
    
    Fixes: 4449f079722c ("PCI: Calculate maximum number of buses required for VFs")
    Based-on-patch-by: Ethan Zhao <ethan.zhao@...cle.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index ee0ebff..0202ab0 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -384,7 +384,7 @@ static int sriov_init(struct pci_dev *dev, int pos)
 	int rc;
 	int nres;
 	u32 pgsz;
-	u16 ctrl, total, offset, stride;
+	u16 ctrl, total;
 	struct pci_sriov *iov;
 	struct resource *res;
 	struct pci_dev *pdev;
@@ -414,11 +414,6 @@ static int sriov_init(struct pci_dev *dev, int pos)
 
 found:
 	pci_write_config_word(dev, pos + PCI_SRIOV_CTRL, ctrl);
-	pci_write_config_word(dev, pos + PCI_SRIOV_NUM_VF, 0);
-	pci_read_config_word(dev, pos + PCI_SRIOV_VF_OFFSET, &offset);
-	pci_read_config_word(dev, pos + PCI_SRIOV_VF_STRIDE, &stride);
-	if (!offset || (total > 1 && !stride))
-		return -EIO;
 
 	pci_read_config_dword(dev, pos + PCI_SRIOV_SUP_PGSIZE, &pgsz);
 	i = PAGE_SHIFT > 12 ? PAGE_SHIFT - 12 : 0;
@@ -456,8 +451,6 @@ found:
 	iov->nres = nres;
 	iov->ctrl = ctrl;
 	iov->total_VFs = total;
-	iov->offset = offset;
-	iov->stride = stride;
 	iov->pgsz = pgsz;
 	iov->self = dev;
 	pci_read_config_dword(dev, pos + PCI_SRIOV_CAP, &iov->cap);
@@ -475,6 +468,11 @@ found:
 	dev->sriov = iov;
 	dev->is_physfn = 1;
 	iov->max_VF_buses = virtfn_max_buses(dev);
+	pci_iov_set_numvfs(dev, 0);
+	if (!iov->offset || (total > 1 && !iov->stride)) {
+		rc = -EIO;
+		goto failed;
+	}
 
 	return 0;
 
@@ -484,6 +482,7 @@ failed:
 		res->flags = 0;
 	}
 
+	dev->sriov = NULL;
 	kfree(iov);
 	return rc;
 }
--
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