pci_rebar_set_size() adjusts BAR size for both normal and IOV BARs. The
struct pci_srvio keeps a cached copy of BAR size in unit of
resource_size_t in ->barsz[] which is not adjusted by
pci_rebar_set_size() but by pci_iov_resource_set_size().
pci_iov_resource_set_size() is called also from
pci_resize_resource_set_size().

The current arrangement is problematic once BAR resize algorithm starts
to roll back changes properly in case of a failure. The normal resource
fitting algorithm rolls back resource size using the struct
pci_dev_resource easily but having to call also
pci_resize_resource_set_size() or pci_iov_resource_set_size() to roll
back BAR size would be an extra burden, whereas combining ->barsz[]
update with pci_rebar_set_size() naturally rolls back it when restoring
the old BAR size on a different layer of the BAR resize operation.

Thus, rework pci_rebar_set_size() to also update ->barsz[].

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
---
 drivers/pci/iov.c       | 15 ++++-----------
 drivers/pci/pci.c       |  4 ++++
 drivers/pci/pci.h       |  5 ++---
 drivers/pci/setup-res.c | 10 ++++------
 4 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/iov.c b/drivers/pci/iov.c
index 77dee43b7858..04b675e90963 100644
--- a/drivers/pci/iov.c
+++ b/drivers/pci/iov.c
@@ -158,8 +158,7 @@ resource_size_t pci_iov_resource_size(struct pci_dev *dev, int resno)
 	return dev->sriov->barsz[pci_resource_num_to_vf_bar(resno)];
 }
 
-void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
-			       resource_size_t size)
+void pci_iov_resource_set_size(struct pci_dev *dev, int resno, int size)
 {
 	if (!pci_resource_is_iov(resno)) {
 		pci_warn(dev, "%s is not an IOV resource\n",
@@ -167,7 +166,8 @@ void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
 		return;
 	}
 
-	dev->sriov->barsz[pci_resource_num_to_vf_bar(resno)] = size;
+	resno = pci_resource_num_to_vf_bar(resno);
+	dev->sriov->barsz[resno] = pci_rebar_size_to_bytes(size);
 }
 
 bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev)
@@ -1340,7 +1340,6 @@ EXPORT_SYMBOL_GPL(pci_sriov_configure_simple);
 int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size)
 {
 	u32 sizes;
-	int ret;
 
 	if (!pci_resource_is_iov(resno))
 		return -EINVAL;
@@ -1355,13 +1354,7 @@ int pci_iov_vf_bar_set_size(struct pci_dev *dev, int resno, int size)
 	if (!(sizes & BIT(size)))
 		return -EINVAL;
 
-	ret = pci_rebar_set_size(dev, resno, size);
-	if (ret)
-		return ret;
-
-	pci_iov_resource_set_size(dev, resno, pci_rebar_size_to_bytes(size));
-
-	return 0;
+	return pci_rebar_set_size(dev, resno, size);
 }
 EXPORT_SYMBOL_GPL(pci_iov_vf_bar_set_size);
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index b14dd064006c..7dfc58b0e55e 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -3803,6 +3803,10 @@ int pci_rebar_set_size(struct pci_dev *pdev, int bar, int size)
 	ctrl &= ~PCI_REBAR_CTRL_BAR_SIZE;
 	ctrl |= FIELD_PREP(PCI_REBAR_CTRL_BAR_SIZE, size);
 	pci_write_config_dword(pdev, pos + PCI_REBAR_CTRL, ctrl);
+
+	if (pci_resource_is_iov(bar))
+		pci_iov_resource_set_size(pdev, bar, size);
+
 	return 0;
 }
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 4492b809094b..bf1a577e9623 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -808,8 +808,7 @@ void pci_iov_update_resource(struct pci_dev *dev, int resno);
 resource_size_t pci_sriov_resource_alignment(struct pci_dev *dev, int resno);
 void pci_restore_iov_state(struct pci_dev *dev);
 int pci_iov_bus_range(struct pci_bus *bus);
-void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
-			       resource_size_t size);
+void pci_iov_resource_set_size(struct pci_dev *dev, int resno, int size);
 bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev);
 static inline u16 pci_iov_vf_rebar_cap(struct pci_dev *dev)
 {
@@ -851,7 +850,7 @@ static inline int pci_iov_bus_range(struct pci_bus *bus)
 	return 0;
 }
 static inline void pci_iov_resource_set_size(struct pci_dev *dev, int resno,
-					     resource_size_t size) { }
+					     int size) { }
 static inline bool pci_iov_is_memory_decoding_enabled(struct pci_dev *dev)
 {
 	return false;
diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index c3ba4ccecd43..3d0b0b3f60c4 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -450,12 +450,10 @@ static void pci_resize_resource_set_size(struct pci_dev *dev, int resno,
 	resource_size_t res_size = pci_rebar_size_to_bytes(size);
 	struct resource *res = pci_resource_n(dev, resno);
 
-	if (!pci_resource_is_iov(resno)) {
-		resource_set_size(res, res_size);
-	} else {
-		resource_set_size(res, res_size * pci_sriov_get_totalvfs(dev));
-		pci_iov_resource_set_size(dev, resno, res_size);
-	}
+	if (pci_resource_is_iov(resno))
+		res_size *= pci_sriov_get_totalvfs(dev);
+
+	resource_set_size(res, res_size);
 }
 
 int pci_resize_resource(struct pci_dev *dev, int resno, int size)
-- 
2.39.5

On Tue, Oct 28, 2025 at 07:35:44PM +0200, Ilpo Järvinen wrote:
> pci_rebar_set_size() adjusts BAR size for both normal and IOV BARs. The
> struct pci_srvio keeps a cached copy of BAR size in unit of
> resource_size_t in ->barsz[] ...

Nit: s/pci_srvio/pci/sriov/  (fixed locally, FYI in case you post a v2)

I'm not sure what "unit of resource_size_t" adds here, maybe could be
removed to just say this?

  struct pci_srvio keeps a cached copy of BAR size in ->barsz[] ...

On Thu, 13 Nov 2025, Bjorn Helgaas wrote:

> On Tue, Oct 28, 2025 at 07:35:44PM +0200, Ilpo Järvinen wrote:
> > pci_rebar_set_size() adjusts BAR size for both normal and IOV BARs. The
> > struct pci_srvio keeps a cached copy of BAR size in unit of
> > resource_size_t in ->barsz[] ...
> 
> Nit: s/pci_srvio/pci/sriov/  (fixed locally, FYI in case you post a v2)

I just posted v2 without seeing this first. :-(

I seem to never learn to type those letters in the correct order, I don't 
know why I always keep typing them wrong.

> I'm not sure what "unit of resource_size_t" adds here, maybe could be
> removed to just say this?
> 
>   struct pci_srvio keeps a cached copy of BAR size in ->barsz[] ...

Seems okay with me. I just had it there to differentiate from "BAR size" 
which happens to often be the format directly compatible with field in the 
capability.

-- 
 i.

On Thu, Nov 13, 2025 at 06:35:26PM +0200, Ilpo Järvinen wrote:
> On Thu, 13 Nov 2025, Bjorn Helgaas wrote:
> 
> > On Tue, Oct 28, 2025 at 07:35:44PM +0200, Ilpo Järvinen wrote:
> > > pci_rebar_set_size() adjusts BAR size for both normal and IOV BARs. The
> > > struct pci_srvio keeps a cached copy of BAR size in unit of
> > > resource_size_t in ->barsz[] ...

> > I'm not sure what "unit of resource_size_t" adds here, maybe could be
> > removed to just say this?
> > 
> >   struct pci_srvio keeps a cached copy of BAR size in ->barsz[] ...
> 
> Seems okay with me. I just had it there to differentiate from "BAR size" 
> which happens to often be the format directly compatible with field in the 
> capability.

Ah, I see now, "size" used to be in bytes, but now it's the encoded
size.

On Thu, Nov 13, 2025 at 06:35:26PM +0200, Ilpo Järvinen wrote:
> On Thu, 13 Nov 2025, Bjorn Helgaas wrote:
> > On Tue, Oct 28, 2025 at 07:35:44PM +0200, Ilpo Järvinen wrote:
> > > pci_rebar_set_size() adjusts BAR size for both normal and IOV BARs. The
> > > struct pci_srvio keeps a cached copy of BAR size in unit of
> > > resource_size_t in ->barsz[] ...
> > 
> > Nit: s/pci_srvio/pci/sriov/  (fixed locally, FYI in case you post a v2)
> 
> I just posted v2 without seeing this first. :-(

Perfect, we crossed in the mail!  I'll tweak this locally.