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SubjectRe: [PATCH kernel] PCI: Disable IOV before pcibios_sriov_disable()
On Fri, Aug 11, 2017 at 06:19:33PM +1000, Alexey Kardashevskiy wrote:
> From: Gavin Shan <gwshan@linux.vnet.ibm.com>
>
> The PowerNV platform is the only user of pcibios_sriov_disable().
> The IOV BAR could be shifted by pci_iov_update_resource(). The
> warning message in the function is printed if the IOV capability
> is in enabled (PCI_SRIOV_CTRL_VFE && PCI_SRIOV_CTRL_MSE) state.
>
> This is the backtrace of what is happening:
> pci_disable_sriov
> sriov_disable
> pnv_pci_sriov_disable
> pnv_pci_vf_resource_shift
> pci_update_resource
> pci_iov_update_resource
>
> This fixes the issue by disabling IOV capability before calling
> pcibios_sriov_disable(). With it, the disabling path matches
> the enabling path: pcibios_sriov_enable() is called before the
> IOV capability is enabled.
>
> Cc: shan.gavin@gmail.com
> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
> Cc: Paul Mackerras <paulus@samba.org>
> Reported-by: Carol L Soto <clsoto@us.ibm.com>
> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
> Tested-by: Carol L Soto <clsoto@us.ibm.com>
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
>
> This is repost. Since Gavin left the team, I am trying to push it out.
> The previos converstion is here: https://patchwork.ozlabs.org/patch/732653/

I gave up on the previous issue. I think this patch makes sense as-is
at least as far as the fact that we can't update a struct resource
while the device is still consuming it. I reworked the changelog to
emphasize that.

I assume the fact that pci_iov_update_resource() dropped the resource
update caused some user-visible issue later on, and I might mention
that, too, if I knew what it was.

Here's what I would consider putting on pci/virtualization (the diff
is unchanged from your post):


commit 08132e7759b3929bea0ccdf8afe81ebf05351389
Author: Gavin Shan <gwshan@linux.vnet.ibm.com>
Date: Fri Aug 11 18:19:33 2017 +1000

PCI: Disable VF decoding before updating resources in pcibios_sriov_disable()

A struct resource represents the address space consumed by a device. We
should not modify that resource while the device is actively using the
address space. For VFs, pci_iov_update_resource() enforces this by
printing a warning and doing nothing if the VFE (VF Enable) and MSE (VF
Memory Space Enable) bits are set.

Previously, both sriov_enable() and sriov_disable() called the
pcibios_sriov_disable() arch hook, which may update the struct resource,
while VFE and MSE were enabled. This effectively dropped the resource
update pcibios_sriov_disable() intended to do.

Disable VF memory decoding before calling pcibios_sriov_disable().

Reported-by: Carol L Soto <clsoto@us.ibm.com>
Tested-by: Carol L Soto <clsoto@us.ibm.com>
Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: shan.gavin@gmail.com
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 120485d6f352..ac41c8be9200 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -331,7 +331,6 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
while (i--)
pci_iov_remove_virtfn(dev, i, 0);

- pcibios_sriov_disable(dev);
err_pcibios:
iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
pci_cfg_access_lock(dev);
@@ -339,6 +338,8 @@ static int sriov_enable(struct pci_dev *dev, int nr_virtfn)
ssleep(1);
pci_cfg_access_unlock(dev);

+ pcibios_sriov_disable(dev);
+
if (iov->link != dev->devfn)
sysfs_remove_link(&dev->dev.kobj, "dep_link");

@@ -357,14 +358,14 @@ static void sriov_disable(struct pci_dev *dev)
for (i = 0; i < iov->num_VFs; i++)
pci_iov_remove_virtfn(dev, i, 0);

- pcibios_sriov_disable(dev);
-
iov->ctrl &= ~(PCI_SRIOV_CTRL_VFE | PCI_SRIOV_CTRL_MSE);
pci_cfg_access_lock(dev);
pci_write_config_word(dev, iov->pos + PCI_SRIOV_CTRL, iov->ctrl);
ssleep(1);
pci_cfg_access_unlock(dev);

+ pcibios_sriov_disable(dev);
+
if (iov->link != dev->devfn)
sysfs_remove_link(&dev->dev.kobj, "dep_link");

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