[PATCH] PCI: Probe bridge window attributes once at enumeration-time

[PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Bjorn Helgaas]

From: Bjorn Helgaas <bhelgaas@google.com>

pci_bridge_check_ranges() determines whether a bridge supports the optional
I/O and prefetchable memory windows and sets the flag bits in the bridge
resources.  This *could* be done once during enumeration except that the
resource allocation code completely clears the flag bits, e.g., in the
pci_assign_unassigned_bridge_resources() path.

The problem with pci_bridge_check_ranges() in the resource allocation path
is that we may allocate resources after devices have been claimed by
drivers, and pci_bridge_check_ranges() *changes* the window registers to
determine whether they're writable.  This may break concurrent accesses to
devices behind the bridge.

Add a new pci_read_bridge_windows() to determine whether a bridge supports
the optional windows, call it once during enumeration, remember the
results, and change pci_bridge_check_ranges() so it doesn't touch the
bridge windows but sets the flag bits based on those remembered results.

Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html
Reported-by: xuyandong <xuyandong2@huawei.com>
Tested-by: xuyandong <xuyandong2@huawei.com>
Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Ofer Hayut <ofer@lightbitslabs.com>
Cc: Roy Shterman <roys@lightbitslabs.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Zhou Wang <wangzhou1@hisilicon.com>
---
 drivers/pci/probe.c     |   52 +++++++++++++++++++++++++++++++++++++++++++++++
 drivers/pci/setup-bus.c |   45 ++++-------------------------------------
 include/linux/pci.h     |    3 +++
 3 files changed, 59 insertions(+), 41 deletions(-)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 257b9f6f2ebb..2ef8b954c65a 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
 	}
 }
 
+static void pci_read_bridge_windows(struct pci_dev *bridge)
+{
+	u16 io;
+	u32 pmem, tmp;
+
+	pci_read_config_word(bridge, PCI_IO_BASE, &io);
+	if (!io) {
+		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
+		pci_read_config_word(bridge, PCI_IO_BASE, &io);
+		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
+	}
+	if (io)
+		bridge->io_window = 1;
+
+	/*
+	 * DECchip 21050 pass 2 errata: the bridge may miss an address
+	 * disconnect boundary by one PCI data phase.  Workaround: do not
+	 * use prefetching on this device.
+	 */
+	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
+		return;
+
+	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
+	if (!pmem) {
+		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
+					       0xffe0fff0);
+		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
+		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
+	}
+	if (!pmem)
+		return;
+
+	bridge->pref_window = 1;
+
+	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
+
+		/*
+		 * Bridge claims to have a 64-bit prefetchable memory
+		 * window; verify that the upper bits are actually
+		 * writable.
+		 */
+		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);
+		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
+				       0xffffffff);
+		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
+		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);
+		if (tmp)
+			bridge->pref_64_window = 1;
+	}
+}
+
 static void pci_read_bridge_io(struct pci_bus *child)
 {
 	struct pci_dev *dev = child->self;
@@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev)
 		pci_read_irq(dev);
 		dev->transparent = ((dev->class & 0xff) == 1);
 		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
+		pci_read_bridge_windows(dev);
 		set_pcie_hotplug_bridge(dev);
 		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
 		if (pos) {
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index ed960436df5e..1941bb0a6c13 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
    base/limit registers must be read-only and read as 0. */
 static void pci_bridge_check_ranges(struct pci_bus *bus)
 {
-	u16 io;
-	u32 pmem;
 	struct pci_dev *bridge = bus->self;
-	struct resource *b_res;
+	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
 
-	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
 	b_res[1].flags |= IORESOURCE_MEM;
 
-	pci_read_config_word(bridge, PCI_IO_BASE, &io);
-	if (!io) {
-		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
-		pci_read_config_word(bridge, PCI_IO_BASE, &io);
-		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
-	}
-	if (io)
+	if (bridge->io_window)
 		b_res[0].flags |= IORESOURCE_IO;
 
-	/*  DECchip 21050 pass 2 errata: the bridge may miss an address
-	    disconnect boundary by one PCI data phase.
-	    Workaround: do not use prefetching on this device. */
-	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
-		return;
-
-	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
-	if (!pmem) {
-		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
-					       0xffe0fff0);
-		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
-		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
-	}
-	if (pmem) {
+	if (bridge->pref_window) {
 		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
-		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
-		    PCI_PREF_RANGE_TYPE_64) {
+		if (bridge->pref_64_window) {
 			b_res[2].flags |= IORESOURCE_MEM_64;
 			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
 		}
 	}
-
-	/* double check if bridge does support 64 bit pref */
-	if (b_res[2].flags & IORESOURCE_MEM_64) {
-		u32 mem_base_hi, tmp;
-		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,
-					 &mem_base_hi);
-		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
-					       0xffffffff);
-		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
-		if (!tmp)
-			b_res[2].flags &= ~IORESOURCE_MEM_64;
-		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
-				       mem_base_hi);
-	}
 }
 
 /* Helper function for sizing routines: find first available
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 65f1d8c2f082..40b327b814aa 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -373,6 +373,9 @@ struct pci_dev {
 	bool		match_driver;		/* Skip attaching driver */
 
 	unsigned int	transparent:1;		/* Subtractive decode bridge */
+	unsigned int	io_window:1;		/* Bridge has I/O window */
+	unsigned int	pref_window:1;		/* Bridge has pref mem window */
+	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */
 	unsigned int	multifunction:1;	/* Multi-function device */
 
 	unsigned int	is_busmaster:1;		/* Is busmaster */

Re: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Bjorn Helgaas]

On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> From: Bjorn Helgaas <bhelgaas@google.com>
> 
> pci_bridge_check_ranges() determines whether a bridge supports the optional
> I/O and prefetchable memory windows and sets the flag bits in the bridge
> resources.  This *could* be done once during enumeration except that the
> resource allocation code completely clears the flag bits, e.g., in the
> pci_assign_unassigned_bridge_resources() path.
> 
> The problem with pci_bridge_check_ranges() in the resource allocation path
> is that we may allocate resources after devices have been claimed by
> drivers, and pci_bridge_check_ranges() *changes* the window registers to
> determine whether they're writable.  This may break concurrent accesses to
> devices behind the bridge.
> 
> Add a new pci_read_bridge_windows() to determine whether a bridge supports
> the optional windows, call it once during enumeration, remember the
> results, and change pci_bridge_check_ranges() so it doesn't touch the
> bridge windows but sets the flag bits based on those remembered results.
> 
> Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
> Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html
> Reported-by: xuyandong <xuyandong2@huawei.com>
> Tested-by: xuyandong <xuyandong2@huawei.com>
> Cc: Sagi Grimberg <sagi@grimberg.me>
> Cc: Ofer Hayut <ofer@lightbitslabs.com>
> Cc: Roy Shterman <roys@lightbitslabs.com>
> Cc: Keith Busch <keith.busch@intel.com>
> Cc: Zhou Wang <wangzhou1@hisilicon.com>

Applied to pci/enumeration for v5.1.

This is fairly simple in concept, but doesn't meet the letter of the
restrictions in Documentation/process/stable-kernel-rules.rst, so I
didn't tag it for stable.

Is there a compelling argument to mark it for stable?

> ---
>  drivers/pci/probe.c     |   52 +++++++++++++++++++++++++++++++++++++++++++++++
>  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
>  include/linux/pci.h     |    3 +++
>  3 files changed, 59 insertions(+), 41 deletions(-)
> 
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 257b9f6f2ebb..2ef8b954c65a 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
>  	}
>  }
>  
> +static void pci_read_bridge_windows(struct pci_dev *bridge)
> +{
> +	u16 io;
> +	u32 pmem, tmp;
> +
> +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> +	if (!io) {
> +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> +	}
> +	if (io)
> +		bridge->io_window = 1;
> +
> +	/*
> +	 * DECchip 21050 pass 2 errata: the bridge may miss an address
> +	 * disconnect boundary by one PCI data phase.  Workaround: do not
> +	 * use prefetching on this device.
> +	 */
> +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> +		return;
> +
> +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> +	if (!pmem) {
> +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> +					       0xffe0fff0);
> +		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> +	}
> +	if (!pmem)
> +		return;
> +
> +	bridge->pref_window = 1;
> +
> +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
> +
> +		/*
> +		 * Bridge claims to have a 64-bit prefetchable memory
> +		 * window; verify that the upper bits are actually
> +		 * writable.
> +		 */
> +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);
> +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> +				       0xffffffff);
> +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);
> +		if (tmp)
> +			bridge->pref_64_window = 1;
> +	}
> +}
> +
>  static void pci_read_bridge_io(struct pci_bus *child)
>  {
>  	struct pci_dev *dev = child->self;
> @@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev)
>  		pci_read_irq(dev);
>  		dev->transparent = ((dev->class & 0xff) == 1);
>  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> +		pci_read_bridge_windows(dev);
>  		set_pcie_hotplug_bridge(dev);
>  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
>  		if (pos) {
> diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> index ed960436df5e..1941bb0a6c13 100644
> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
>     base/limit registers must be read-only and read as 0. */
>  static void pci_bridge_check_ranges(struct pci_bus *bus)
>  {
> -	u16 io;
> -	u32 pmem;
>  	struct pci_dev *bridge = bus->self;
> -	struct resource *b_res;
> +	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
>  
> -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
>  	b_res[1].flags |= IORESOURCE_MEM;
>  
> -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> -	if (!io) {
> -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> -	}
> -	if (io)
> +	if (bridge->io_window)
>  		b_res[0].flags |= IORESOURCE_IO;
>  
> -	/*  DECchip 21050 pass 2 errata: the bridge may miss an address
> -	    disconnect boundary by one PCI data phase.
> -	    Workaround: do not use prefetching on this device. */
> -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> -		return;
> -
> -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> -	if (!pmem) {
> -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> -					       0xffe0fff0);
> -		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> -	}
> -	if (pmem) {
> +	if (bridge->pref_window) {
>  		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
> -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> -		    PCI_PREF_RANGE_TYPE_64) {
> +		if (bridge->pref_64_window) {
>  			b_res[2].flags |= IORESOURCE_MEM_64;
>  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
>  		}
>  	}
> -
> -	/* double check if bridge does support 64 bit pref */
> -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> -		u32 mem_base_hi, tmp;
> -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> -					 &mem_base_hi);
> -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> -					       0xffffffff);
> -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> -		if (!tmp)
> -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> -				       mem_base_hi);
> -	}
>  }
>  
>  /* Helper function for sizing routines: find first available
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 65f1d8c2f082..40b327b814aa 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -373,6 +373,9 @@ struct pci_dev {
>  	bool		match_driver;		/* Skip attaching driver */
>  
>  	unsigned int	transparent:1;		/* Subtractive decode bridge */
> +	unsigned int	io_window:1;		/* Bridge has I/O window */
> +	unsigned int	pref_window:1;		/* Bridge has pref mem window */
> +	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */
>  	unsigned int	multifunction:1;	/* Multi-function device */
>  
>  	unsigned int	is_busmaster:1;		/* Is busmaster */
> 

Re: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Michael S. Tsirkin]

On Tue, Jan 29, 2019 at 04:43:33PM -0600, Bjorn Helgaas wrote:
> On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@google.com>
> > 
> > pci_bridge_check_ranges() determines whether a bridge supports the optional
> > I/O and prefetchable memory windows and sets the flag bits in the bridge
> > resources.  This *could* be done once during enumeration except that the
> > resource allocation code completely clears the flag bits, e.g., in the
> > pci_assign_unassigned_bridge_resources() path.
> > 
> > The problem with pci_bridge_check_ranges() in the resource allocation path
> > is that we may allocate resources after devices have been claimed by
> > drivers, and pci_bridge_check_ranges() *changes* the window registers to
> > determine whether they're writable.  This may break concurrent accesses to
> > devices behind the bridge.
> > 
> > Add a new pci_read_bridge_windows() to determine whether a bridge supports
> > the optional windows, call it once during enumeration, remember the
> > results, and change pci_bridge_check_ranges() so it doesn't touch the
> > bridge windows but sets the flag bits based on those remembered results.
> > 
> > Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
> > Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html
> > Reported-by: xuyandong <xuyandong2@huawei.com>
> > Tested-by: xuyandong <xuyandong2@huawei.com>
> > Cc: Sagi Grimberg <sagi@grimberg.me>
> > Cc: Ofer Hayut <ofer@lightbitslabs.com>
> > Cc: Roy Shterman <roys@lightbitslabs.com>
> > Cc: Keith Busch <keith.busch@intel.com>
> > Cc: Zhou Wang <wangzhou1@hisilicon.com>
> 
> Applied to pci/enumeration for v5.1.
> 
> This is fairly simple in concept, but doesn't meet the letter of the
> restrictions in Documentation/process/stable-kernel-rules.rst, so I
> didn't tag it for stable.
> 
> Is there a compelling argument to mark it for stable?

Well it's needed downstream.
It's a bit above 100 lines with context. Is this what you mean?
If yes how about using my patch for stable as an alternative?
The rules allow for equivalent patches.


> > ---
> >  drivers/pci/probe.c     |   52 +++++++++++++++++++++++++++++++++++++++++++++++
> >  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
> >  include/linux/pci.h     |    3 +++
> >  3 files changed, 59 insertions(+), 41 deletions(-)
> > 
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index 257b9f6f2ebb..2ef8b954c65a 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
> >  	}
> >  }
> >  
> > +static void pci_read_bridge_windows(struct pci_dev *bridge)
> > +{
> > +	u16 io;
> > +	u32 pmem, tmp;
> > +
> > +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > +	if (!io) {
> > +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > +	}
> > +	if (io)
> > +		bridge->io_window = 1;
> > +
> > +	/*
> > +	 * DECchip 21050 pass 2 errata: the bridge may miss an address
> > +	 * disconnect boundary by one PCI data phase.  Workaround: do not
> > +	 * use prefetching on this device.
> > +	 */
> > +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > +		return;
> > +
> > +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > +	if (!pmem) {
> > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > +					       0xffe0fff0);
> > +		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > +	}
> > +	if (!pmem)
> > +		return;
> > +
> > +	bridge->pref_window = 1;
> > +
> > +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
> > +
> > +		/*
> > +		 * Bridge claims to have a 64-bit prefetchable memory
> > +		 * window; verify that the upper bits are actually
> > +		 * writable.
> > +		 */
> > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);
> > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > +				       0xffffffff);
> > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);
> > +		if (tmp)
> > +			bridge->pref_64_window = 1;
> > +	}
> > +}
> > +
> >  static void pci_read_bridge_io(struct pci_bus *child)
> >  {
> >  	struct pci_dev *dev = child->self;
> > @@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev)
> >  		pci_read_irq(dev);
> >  		dev->transparent = ((dev->class & 0xff) == 1);
> >  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> > +		pci_read_bridge_windows(dev);
> >  		set_pcie_hotplug_bridge(dev);
> >  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
> >  		if (pos) {
> > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > index ed960436df5e..1941bb0a6c13 100644
> > --- a/drivers/pci/setup-bus.c
> > +++ b/drivers/pci/setup-bus.c
> > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
> >     base/limit registers must be read-only and read as 0. */
> >  static void pci_bridge_check_ranges(struct pci_bus *bus)
> >  {
> > -	u16 io;
> > -	u32 pmem;
> >  	struct pci_dev *bridge = bus->self;
> > -	struct resource *b_res;
> > +	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> >  
> > -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> >  	b_res[1].flags |= IORESOURCE_MEM;
> >  
> > -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > -	if (!io) {
> > -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > -	}
> > -	if (io)
> > +	if (bridge->io_window)
> >  		b_res[0].flags |= IORESOURCE_IO;
> >  
> > -	/*  DECchip 21050 pass 2 errata: the bridge may miss an address
> > -	    disconnect boundary by one PCI data phase.
> > -	    Workaround: do not use prefetching on this device. */
> > -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > -		return;
> > -
> > -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > -	if (!pmem) {
> > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > -					       0xffe0fff0);
> > -		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > -	}
> > -	if (pmem) {
> > +	if (bridge->pref_window) {
> >  		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
> > -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > -		    PCI_PREF_RANGE_TYPE_64) {
> > +		if (bridge->pref_64_window) {
> >  			b_res[2].flags |= IORESOURCE_MEM_64;
> >  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> >  		}
> >  	}
> > -
> > -	/* double check if bridge does support 64 bit pref */
> > -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> > -		u32 mem_base_hi, tmp;
> > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > -					 &mem_base_hi);
> > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > -					       0xffffffff);
> > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > -		if (!tmp)
> > -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > -				       mem_base_hi);
> > -	}
> >  }
> >  
> >  /* Helper function for sizing routines: find first available
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 65f1d8c2f082..40b327b814aa 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -373,6 +373,9 @@ struct pci_dev {
> >  	bool		match_driver;		/* Skip attaching driver */
> >  
> >  	unsigned int	transparent:1;		/* Subtractive decode bridge */
> > +	unsigned int	io_window:1;		/* Bridge has I/O window */
> > +	unsigned int	pref_window:1;		/* Bridge has pref mem window */
> > +	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */
> >  	unsigned int	multifunction:1;	/* Multi-function device */
> >  
> >  	unsigned int	is_busmaster:1;		/* Is busmaster */
> > 

Re: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Bjorn Helgaas]

On Tue, Jan 29, 2019 at 05:47:32PM -0500, Michael S. Tsirkin wrote:
> On Tue, Jan 29, 2019 at 04:43:33PM -0600, Bjorn Helgaas wrote:
> > On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > 
> > > pci_bridge_check_ranges() determines whether a bridge supports the optional
> > > I/O and prefetchable memory windows and sets the flag bits in the bridge
> > > resources.  This *could* be done once during enumeration except that the
> > > resource allocation code completely clears the flag bits, e.g., in the
> > > pci_assign_unassigned_bridge_resources() path.
> > > 
> > > The problem with pci_bridge_check_ranges() in the resource allocation path
> > > is that we may allocate resources after devices have been claimed by
> > > drivers, and pci_bridge_check_ranges() *changes* the window registers to
> > > determine whether they're writable.  This may break concurrent accesses to
> > > devices behind the bridge.
> > > 
> > > Add a new pci_read_bridge_windows() to determine whether a bridge supports
> > > the optional windows, call it once during enumeration, remember the
> > > results, and change pci_bridge_check_ranges() so it doesn't touch the
> > > bridge windows but sets the flag bits based on those remembered results.
> > > 
> > > Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
> > > Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html
> > > Reported-by: xuyandong <xuyandong2@huawei.com>
> > > Tested-by: xuyandong <xuyandong2@huawei.com>
> > > Cc: Sagi Grimberg <sagi@grimberg.me>
> > > Cc: Ofer Hayut <ofer@lightbitslabs.com>
> > > Cc: Roy Shterman <roys@lightbitslabs.com>
> > > Cc: Keith Busch <keith.busch@intel.com>
> > > Cc: Zhou Wang <wangzhou1@hisilicon.com>
> > 
> > Applied to pci/enumeration for v5.1.
> > 
> > This is fairly simple in concept, but doesn't meet the letter of the
> > restrictions in Documentation/process/stable-kernel-rules.rst, so I
> > didn't tag it for stable.
> > 
> > Is there a compelling argument to mark it for stable?
> 
> Well it's needed downstream.
> It's a bit above 100 lines with context. Is this what you mean?

Yep, I should have been explicit about that.

> If yes how about using my patch for stable as an alternative?
> The rules allow for equivalent patches.

Well, yes, that would be a possibility.

I would rather develop an argument for marking *this* patch for
stable.  Even though it is technically too large, I think we could
make it work if we have compelling reasons.

Those would need to be fleshed out a little more than "needed
downstream" -- something about the scenarios where this happens, what
the serious problem is, etc.

The *ideal* thing would be to have an actual bugzilla.kernel.org
report of the problem with a way to reproduce it and dmesg
illustrating the problem.

> > > ---
> > >  drivers/pci/probe.c     |   52 +++++++++++++++++++++++++++++++++++++++++++++++
> > >  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
> > >  include/linux/pci.h     |    3 +++
> > >  3 files changed, 59 insertions(+), 41 deletions(-)
> > > 
> > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > > index 257b9f6f2ebb..2ef8b954c65a 100644
> > > --- a/drivers/pci/probe.c
> > > +++ b/drivers/pci/probe.c
> > > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
> > >  	}
> > >  }
> > >  
> > > +static void pci_read_bridge_windows(struct pci_dev *bridge)
> > > +{
> > > +	u16 io;
> > > +	u32 pmem, tmp;
> > > +
> > > +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > +	if (!io) {
> > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > +	}
> > > +	if (io)
> > > +		bridge->io_window = 1;
> > > +
> > > +	/*
> > > +	 * DECchip 21050 pass 2 errata: the bridge may miss an address
> > > +	 * disconnect boundary by one PCI data phase.  Workaround: do not
> > > +	 * use prefetching on this device.
> > > +	 */
> > > +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > > +		return;
> > > +
> > > +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > +	if (!pmem) {
> > > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > > +					       0xffe0fff0);
> > > +		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > > +	}
> > > +	if (!pmem)
> > > +		return;
> > > +
> > > +	bridge->pref_window = 1;
> > > +
> > > +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
> > > +
> > > +		/*
> > > +		 * Bridge claims to have a 64-bit prefetchable memory
> > > +		 * window; verify that the upper bits are actually
> > > +		 * writable.
> > > +		 */
> > > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);
> > > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > +				       0xffffffff);
> > > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);
> > > +		if (tmp)
> > > +			bridge->pref_64_window = 1;
> > > +	}
> > > +}
> > > +
> > >  static void pci_read_bridge_io(struct pci_bus *child)
> > >  {
> > >  	struct pci_dev *dev = child->self;
> > > @@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev)
> > >  		pci_read_irq(dev);
> > >  		dev->transparent = ((dev->class & 0xff) == 1);
> > >  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> > > +		pci_read_bridge_windows(dev);
> > >  		set_pcie_hotplug_bridge(dev);
> > >  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
> > >  		if (pos) {
> > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > > index ed960436df5e..1941bb0a6c13 100644
> > > --- a/drivers/pci/setup-bus.c
> > > +++ b/drivers/pci/setup-bus.c
> > > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
> > >     base/limit registers must be read-only and read as 0. */
> > >  static void pci_bridge_check_ranges(struct pci_bus *bus)
> > >  {
> > > -	u16 io;
> > > -	u32 pmem;
> > >  	struct pci_dev *bridge = bus->self;
> > > -	struct resource *b_res;
> > > +	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > >  
> > > -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > >  	b_res[1].flags |= IORESOURCE_MEM;
> > >  
> > > -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > -	if (!io) {
> > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > -	}
> > > -	if (io)
> > > +	if (bridge->io_window)
> > >  		b_res[0].flags |= IORESOURCE_IO;
> > >  
> > > -	/*  DECchip 21050 pass 2 errata: the bridge may miss an address
> > > -	    disconnect boundary by one PCI data phase.
> > > -	    Workaround: do not use prefetching on this device. */
> > > -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > > -		return;
> > > -
> > > -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > -	if (!pmem) {
> > > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > > -					       0xffe0fff0);
> > > -		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > > -	}
> > > -	if (pmem) {
> > > +	if (bridge->pref_window) {
> > >  		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
> > > -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > -		    PCI_PREF_RANGE_TYPE_64) {
> > > +		if (bridge->pref_64_window) {
> > >  			b_res[2].flags |= IORESOURCE_MEM_64;
> > >  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> > >  		}
> > >  	}
> > > -
> > > -	/* double check if bridge does support 64 bit pref */
> > > -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> > > -		u32 mem_base_hi, tmp;
> > > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > -					 &mem_base_hi);
> > > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > -					       0xffffffff);
> > > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > > -		if (!tmp)
> > > -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> > > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > -				       mem_base_hi);
> > > -	}
> > >  }
> > >  
> > >  /* Helper function for sizing routines: find first available
> > > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > > index 65f1d8c2f082..40b327b814aa 100644
> > > --- a/include/linux/pci.h
> > > +++ b/include/linux/pci.h
> > > @@ -373,6 +373,9 @@ struct pci_dev {
> > >  	bool		match_driver;		/* Skip attaching driver */
> > >  
> > >  	unsigned int	transparent:1;		/* Subtractive decode bridge */
> > > +	unsigned int	io_window:1;		/* Bridge has I/O window */
> > > +	unsigned int	pref_window:1;		/* Bridge has pref mem window */
> > > +	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */
> > >  	unsigned int	multifunction:1;	/* Multi-function device */
> > >  
> > >  	unsigned int	is_busmaster:1;		/* Is busmaster */
> > > 

Re: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Michael S. Tsirkin]

On Tue, Jan 29, 2019 at 05:02:26PM -0600, Bjorn Helgaas wrote:
> On Tue, Jan 29, 2019 at 05:47:32PM -0500, Michael S. Tsirkin wrote:
> > On Tue, Jan 29, 2019 at 04:43:33PM -0600, Bjorn Helgaas wrote:
> > > On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > > 
> > > > pci_bridge_check_ranges() determines whether a bridge supports the optional
> > > > I/O and prefetchable memory windows and sets the flag bits in the bridge
> > > > resources.  This *could* be done once during enumeration except that the
> > > > resource allocation code completely clears the flag bits, e.g., in the
> > > > pci_assign_unassigned_bridge_resources() path.
> > > > 
> > > > The problem with pci_bridge_check_ranges() in the resource allocation path
> > > > is that we may allocate resources after devices have been claimed by
> > > > drivers, and pci_bridge_check_ranges() *changes* the window registers to
> > > > determine whether they're writable.  This may break concurrent accesses to
> > > > devices behind the bridge.
> > > > 
> > > > Add a new pci_read_bridge_windows() to determine whether a bridge supports
> > > > the optional windows, call it once during enumeration, remember the
> > > > results, and change pci_bridge_check_ranges() so it doesn't touch the
> > > > bridge windows but sets the flag bits based on those remembered results.
> > > > 
> > > > Link: https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-email-wangzhou1@hisilicon.com
> > > > Link: https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.html
> > > > Reported-by: xuyandong <xuyandong2@huawei.com>
> > > > Tested-by: xuyandong <xuyandong2@huawei.com>
> > > > Cc: Sagi Grimberg <sagi@grimberg.me>
> > > > Cc: Ofer Hayut <ofer@lightbitslabs.com>
> > > > Cc: Roy Shterman <roys@lightbitslabs.com>
> > > > Cc: Keith Busch <keith.busch@intel.com>
> > > > Cc: Zhou Wang <wangzhou1@hisilicon.com>
> > > 
> > > Applied to pci/enumeration for v5.1.
> > > 
> > > This is fairly simple in concept, but doesn't meet the letter of the
> > > restrictions in Documentation/process/stable-kernel-rules.rst, so I
> > > didn't tag it for stable.
> > > 
> > > Is there a compelling argument to mark it for stable?
> > 
> > Well it's needed downstream.
> > It's a bit above 100 lines with context. Is this what you mean?
> 
> Yep, I should have been explicit about that.
> 
> > If yes how about using my patch for stable as an alternative?
> > The rules allow for equivalent patches.
> 
> Well, yes, that would be a possibility.
> 
> I would rather develop an argument for marking *this* patch for
> stable.  Even though it is technically too large, I think we could
> make it work if we have compelling reasons.
> 
> Those would need to be fleshed out a little more than "needed
> downstream" -- something about the scenarios where this happens, what
> the serious problem is, etc.
> 
> The *ideal* thing would be to have an actual bugzilla.kernel.org
> report of the problem with a way to reproduce it and dmesg
> illustrating the problem.

xuyandong would you like to take a stub at creating the bugzilla
entry?
If not let me know and I'll do it.
Thanks!


> > > > ---
> > > >  drivers/pci/probe.c     |   52 +++++++++++++++++++++++++++++++++++++++++++++++
> > > >  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
> > > >  include/linux/pci.h     |    3 +++
> > > >  3 files changed, 59 insertions(+), 41 deletions(-)
> > > > 
> > > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > > > index 257b9f6f2ebb..2ef8b954c65a 100644
> > > > --- a/drivers/pci/probe.c
> > > > +++ b/drivers/pci/probe.c
> > > > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev, unsigned int howmany, int rom)
> > > >  	}
> > > >  }
> > > >  
> > > > +static void pci_read_bridge_windows(struct pci_dev *bridge)
> > > > +{
> > > > +	u16 io;
> > > > +	u32 pmem, tmp;
> > > > +
> > > > +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > +	if (!io) {
> > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > +	}
> > > > +	if (io)
> > > > +		bridge->io_window = 1;
> > > > +
> > > > +	/*
> > > > +	 * DECchip 21050 pass 2 errata: the bridge may miss an address
> > > > +	 * disconnect boundary by one PCI data phase.  Workaround: do not
> > > > +	 * use prefetching on this device.
> > > > +	 */
> > > > +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > > > +		return;
> > > > +
> > > > +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > > +	if (!pmem) {
> > > > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > > > +					       0xffe0fff0);
> > > > +		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > > +		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > > > +	}
> > > > +	if (!pmem)
> > > > +		return;
> > > > +
> > > > +	bridge->pref_window = 1;
> > > > +
> > > > +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) == PCI_PREF_RANGE_TYPE_64) {
> > > > +
> > > > +		/*
> > > > +		 * Bridge claims to have a 64-bit prefetchable memory
> > > > +		 * window; verify that the upper bits are actually
> > > > +		 * writable.
> > > > +		 */
> > > > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &pmem);
> > > > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > > +				       0xffffffff);
> > > > +		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > > > +		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, pmem);
> > > > +		if (tmp)
> > > > +			bridge->pref_64_window = 1;
> > > > +	}
> > > > +}
> > > > +
> > > >  static void pci_read_bridge_io(struct pci_bus *child)
> > > >  {
> > > >  	struct pci_dev *dev = child->self;
> > > > @@ -1739,6 +1790,7 @@ int pci_setup_device(struct pci_dev *dev)
> > > >  		pci_read_irq(dev);
> > > >  		dev->transparent = ((dev->class & 0xff) == 1);
> > > >  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> > > > +		pci_read_bridge_windows(dev);
> > > >  		set_pcie_hotplug_bridge(dev);
> > > >  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
> > > >  		if (pos) {
> > > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > > > index ed960436df5e..1941bb0a6c13 100644
> > > > --- a/drivers/pci/setup-bus.c
> > > > +++ b/drivers/pci/setup-bus.c
> > > > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev *bridge, int i)
> > > >     base/limit registers must be read-only and read as 0. */
> > > >  static void pci_bridge_check_ranges(struct pci_bus *bus)
> > > >  {
> > > > -	u16 io;
> > > > -	u32 pmem;
> > > >  	struct pci_dev *bridge = bus->self;
> > > > -	struct resource *b_res;
> > > > +	struct resource *b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > > >  
> > > > -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > > >  	b_res[1].flags |= IORESOURCE_MEM;
> > > >  
> > > > -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > -	if (!io) {
> > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > -	}
> > > > -	if (io)
> > > > +	if (bridge->io_window)
> > > >  		b_res[0].flags |= IORESOURCE_IO;
> > > >  
> > > > -	/*  DECchip 21050 pass 2 errata: the bridge may miss an address
> > > > -	    disconnect boundary by one PCI data phase.
> > > > -	    Workaround: do not use prefetching on this device. */
> > > > -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device == 0x0001)
> > > > -		return;
> > > > -
> > > > -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > > -	if (!pmem) {
> > > > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > > > -					       0xffe0fff0);
> > > > -		pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE, &pmem);
> > > > -		pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, 0x0);
> > > > -	}
> > > > -	if (pmem) {
> > > > +	if (bridge->pref_window) {
> > > >  		b_res[2].flags |= IORESOURCE_MEM | IORESOURCE_PREFETCH;
> > > > -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > > -		    PCI_PREF_RANGE_TYPE_64) {
> > > > +		if (bridge->pref_64_window) {
> > > >  			b_res[2].flags |= IORESOURCE_MEM_64;
> > > >  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> > > >  		}
> > > >  	}
> > > > -
> > > > -	/* double check if bridge does support 64 bit pref */
> > > > -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> > > > -		u32 mem_base_hi, tmp;
> > > > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > > -					 &mem_base_hi);
> > > > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > > -					       0xffffffff);
> > > > -		pci_read_config_dword(bridge, PCI_PREF_BASE_UPPER32, &tmp);
> > > > -		if (!tmp)
> > > > -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> > > > -		pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32,
> > > > -				       mem_base_hi);
> > > > -	}
> > > >  }
> > > >  
> > > >  /* Helper function for sizing routines: find first available
> > > > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > > > index 65f1d8c2f082..40b327b814aa 100644
> > > > --- a/include/linux/pci.h
> > > > +++ b/include/linux/pci.h
> > > > @@ -373,6 +373,9 @@ struct pci_dev {
> > > >  	bool		match_driver;		/* Skip attaching driver */
> > > >  
> > > >  	unsigned int	transparent:1;		/* Subtractive decode bridge */
> > > > +	unsigned int	io_window:1;		/* Bridge has I/O window */
> > > > +	unsigned int	pref_window:1;		/* Bridge has pref mem window */
> > > > +	unsigned int	pref_64_window:1;	/* Pref mem window is 64-bit */
> > > >  	unsigned int	multifunction:1;	/* Multi-function device */
> > > >  
> > > >  	unsigned int	is_busmaster:1;		/* Is busmaster */
> > > > 

RE: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Xuyandong (Yandong Xu, Euler5)]

> On Tue, Jan 29, 2019 at 05:02:26PM -0600, Bjorn Helgaas wrote:
> > On Tue, Jan 29, 2019 at 05:47:32PM -0500, Michael S. Tsirkin wrote:
> > > On Tue, Jan 29, 2019 at 04:43:33PM -0600, Bjorn Helgaas wrote:
> > > > On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> > > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > > >
> > > > > pci_bridge_check_ranges() determines whether a bridge supports
> > > > > the optional I/O and prefetchable memory windows and sets the
> > > > > flag bits in the bridge resources.  This *could* be done once
> > > > > during enumeration except that the resource allocation code
> > > > > completely clears the flag bits, e.g., in the
> > > > > pci_assign_unassigned_bridge_resources() path.
> > > > >
> > > > > The problem with pci_bridge_check_ranges() in the resource
> > > > > allocation path is that we may allocate resources after devices
> > > > > have been claimed by drivers, and pci_bridge_check_ranges()
> > > > > *changes* the window registers to determine whether they're
> > > > > writable.  This may break concurrent accesses to devices behind the
> bridge.
> > > > >
> > > > > Add a new pci_read_bridge_windows() to determine whether a
> > > > > bridge supports the optional windows, call it once during
> > > > > enumeration, remember the results, and change
> > > > > pci_bridge_check_ranges() so it doesn't touch the bridge windows but
> sets the flag bits based on those remembered results.
> > > > >
> > > > > Link:
> > > > > https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-e
> > > > > mail-wangzhou1@hisilicon.com
> > > > > Link:
> > > > > https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.h
> > > > > tml
> > > > > Reported-by: xuyandong <xuyandong2@huawei.com>
> > > > > Tested-by: xuyandong <xuyandong2@huawei.com>
> > > > > Cc: Sagi Grimberg <sagi@grimberg.me>
> > > > > Cc: Ofer Hayut <ofer@lightbitslabs.com>
> > > > > Cc: Roy Shterman <roys@lightbitslabs.com>
> > > > > Cc: Keith Busch <keith.busch@intel.com>
> > > > > Cc: Zhou Wang <wangzhou1@hisilicon.com>
> > > >
> > > > Applied to pci/enumeration for v5.1.
> > > >
> > > > This is fairly simple in concept, but doesn't meet the letter of
> > > > the restrictions in Documentation/process/stable-kernel-rules.rst,
> > > > so I didn't tag it for stable.
> > > >
> > > > Is there a compelling argument to mark it for stable?
> > >
> > > Well it's needed downstream.
> > > It's a bit above 100 lines with context. Is this what you mean?
> >
> > Yep, I should have been explicit about that.
> >
> > > If yes how about using my patch for stable as an alternative?
> > > The rules allow for equivalent patches.
> >
> > Well, yes, that would be a possibility.
> >
> > I would rather develop an argument for marking *this* patch for
> > stable.  Even though it is technically too large, I think we could
> > make it work if we have compelling reasons.
> >
> > Those would need to be fleshed out a little more than "needed
> > downstream" -- something about the scenarios where this happens, what
> > the serious problem is, etc.
> >
> > The *ideal* thing would be to have an actual bugzilla.kernel.org
> > report of the problem with a way to reproduce it and dmesg
> > illustrating the problem.
> 
> xuyandong would you like to take a stub at creating the bugzilla entry?
> If not let me know and I'll do it.
> Thanks!
> 
Thanks, but I  do not want to create the bugzilla entry.


> 
> > > > > ---
> > > > >  drivers/pci/probe.c     |   52
> +++++++++++++++++++++++++++++++++++++++++++++++
> > > > >  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
> > > > >  include/linux/pci.h     |    3 +++
> > > > >  3 files changed, 59 insertions(+), 41 deletions(-)
> > > > >
> > > > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index
> > > > > 257b9f6f2ebb..2ef8b954c65a 100644
> > > > > --- a/drivers/pci/probe.c
> > > > > +++ b/drivers/pci/probe.c
> > > > > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev,
> unsigned int howmany, int rom)
> > > > >  	}
> > > > >  }
> > > > >
> > > > > +static void pci_read_bridge_windows(struct pci_dev *bridge) {
> > > > > +	u16 io;
> > > > > +	u32 pmem, tmp;
> > > > > +
> > > > > +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > +	if (!io) {
> > > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > > +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > > +	}
> > > > > +	if (io)
> > > > > +		bridge->io_window = 1;
> > > > > +
> > > > > +	/*
> > > > > +	 * DECchip 21050 pass 2 errata: the bridge may miss an
> address
> > > > > +	 * disconnect boundary by one PCI data phase.  Workaround:
> do not
> > > > > +	 * use prefetching on this device.
> > > > > +	 */
> > > > > +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device
> == 0x0001)
> > > > > +		return;
> > > > > +
> > > > > +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> &pmem);
> > > > > +	if (!pmem) {
> > > > > +		pci_write_config_dword(bridge,
> PCI_PREF_MEMORY_BASE,
> > > > > +					       0xffe0fff0);
> > > > > +		pci_read_config_dword(bridge,
> PCI_PREF_MEMORY_BASE, &pmem);
> > > > > +		pci_write_config_dword(bridge,
> PCI_PREF_MEMORY_BASE, 0x0);
> > > > > +	}
> > > > > +	if (!pmem)
> > > > > +		return;
> > > > > +
> > > > > +	bridge->pref_window = 1;
> > > > > +
> > > > > +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > > > +PCI_PREF_RANGE_TYPE_64) {
> > > > > +
> > > > > +		/*
> > > > > +		 * Bridge claims to have a 64-bit prefetchable memory
> > > > > +		 * window; verify that the upper bits are actually
> > > > > +		 * writable.
> > > > > +		 */
> > > > > +		pci_read_config_dword(bridge,
> PCI_PREF_BASE_UPPER32, &pmem);
> > > > > +		pci_write_config_dword(bridge,
> PCI_PREF_BASE_UPPER32,
> > > > > +				       0xffffffff);
> > > > > +		pci_read_config_dword(bridge,
> PCI_PREF_BASE_UPPER32, &tmp);
> > > > > +		pci_write_config_dword(bridge,
> PCI_PREF_BASE_UPPER32, pmem);
> > > > > +		if (tmp)
> > > > > +			bridge->pref_64_window = 1;
> > > > > +	}
> > > > > +}
> > > > > +
> > > > >  static void pci_read_bridge_io(struct pci_bus *child)  {
> > > > >  	struct pci_dev *dev = child->self; @@ -1739,6 +1790,7 @@ int
> > > > > pci_setup_device(struct pci_dev *dev)
> > > > >  		pci_read_irq(dev);
> > > > >  		dev->transparent = ((dev->class & 0xff) == 1);
> > > > >  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> > > > > +		pci_read_bridge_windows(dev);
> > > > >  		set_pcie_hotplug_bridge(dev);
> > > > >  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
> > > > >  		if (pos) {
> > > > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > > > > index ed960436df5e..1941bb0a6c13 100644
> > > > > --- a/drivers/pci/setup-bus.c
> > > > > +++ b/drivers/pci/setup-bus.c
> > > > > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev
> *bridge, int i)
> > > > >     base/limit registers must be read-only and read as 0. */
> > > > > static void pci_bridge_check_ranges(struct pci_bus *bus)  {
> > > > > -	u16 io;
> > > > > -	u32 pmem;
> > > > >  	struct pci_dev *bridge = bus->self;
> > > > > -	struct resource *b_res;
> > > > > +	struct resource *b_res =
> > > > > +&bridge->resource[PCI_BRIDGE_RESOURCES];
> > > > >
> > > > > -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > > > >  	b_res[1].flags |= IORESOURCE_MEM;
> > > > >
> > > > > -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > -	if (!io) {
> > > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > > -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > > -	}
> > > > > -	if (io)
> > > > > +	if (bridge->io_window)
> > > > >  		b_res[0].flags |= IORESOURCE_IO;
> > > > >
> > > > > -	/*  DECchip 21050 pass 2 errata: the bridge may miss an
> address
> > > > > -	    disconnect boundary by one PCI data phase.
> > > > > -	    Workaround: do not use prefetching on this device. */
> > > > > -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device
> == 0x0001)
> > > > > -		return;
> > > > > -
> > > > > -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> &pmem);
> > > > > -	if (!pmem) {
> > > > > -		pci_write_config_dword(bridge,
> PCI_PREF_MEMORY_BASE,
> > > > > -					       0xffe0fff0);
> > > > > -		pci_read_config_dword(bridge,
> PCI_PREF_MEMORY_BASE, &pmem);
> > > > > -		pci_write_config_dword(bridge,
> PCI_PREF_MEMORY_BASE, 0x0);
> > > > > -	}
> > > > > -	if (pmem) {
> > > > > +	if (bridge->pref_window) {
> > > > >  		b_res[2].flags |= IORESOURCE_MEM |
> IORESOURCE_PREFETCH;
> > > > > -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > > > -		    PCI_PREF_RANGE_TYPE_64) {
> > > > > +		if (bridge->pref_64_window) {
> > > > >  			b_res[2].flags |= IORESOURCE_MEM_64;
> > > > >  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> > > > >  		}
> > > > >  	}
> > > > > -
> > > > > -	/* double check if bridge does support 64 bit pref */
> > > > > -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> > > > > -		u32 mem_base_hi, tmp;
> > > > > -		pci_read_config_dword(bridge,
> PCI_PREF_BASE_UPPER32,
> > > > > -					 &mem_base_hi);
> > > > > -		pci_write_config_dword(bridge,
> PCI_PREF_BASE_UPPER32,
> > > > > -					       0xffffffff);
> > > > > -		pci_read_config_dword(bridge,
> PCI_PREF_BASE_UPPER32, &tmp);
> > > > > -		if (!tmp)
> > > > > -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> > > > > -		pci_write_config_dword(bridge,
> PCI_PREF_BASE_UPPER32,
> > > > > -				       mem_base_hi);
> > > > > -	}
> > > > >  }
> > > > >
> > > > >  /* Helper function for sizing routines: find first available
> > > > > diff --git a/include/linux/pci.h b/include/linux/pci.h index
> > > > > 65f1d8c2f082..40b327b814aa 100644
> > > > > --- a/include/linux/pci.h
> > > > > +++ b/include/linux/pci.h
> > > > > @@ -373,6 +373,9 @@ struct pci_dev {
> > > > >  	bool		match_driver;		/* Skip attaching
> driver */
> > > > >
> > > > >  	unsigned int	transparent:1;		/* Subtractive decode
> bridge */
> > > > > +	unsigned int	io_window:1;		/* Bridge has I/O
> window */
> > > > > +	unsigned int	pref_window:1;		/* Bridge has pref
> mem window */
> > > > > +	unsigned int	pref_64_window:1;	/* Pref mem window
> is 64-bit */
> > > > >  	unsigned int	multifunction:1;	/* Multi-function device */
> > > > >
> > > > >  	unsigned int	is_busmaster:1;		/* Is busmaster */
> > > > >

Re: [PATCH] PCI: Probe bridge window attributes once at enumeration-time

[Michael S. Tsirkin]

On Mon, Feb 11, 2019 at 01:57:20AM +0000, Xuyandong (Yandong Xu, Euler5) wrote:
> > On Tue, Jan 29, 2019 at 05:02:26PM -0600, Bjorn Helgaas wrote:
> > > On Tue, Jan 29, 2019 at 05:47:32PM -0500, Michael S. Tsirkin wrote:
> > > > On Tue, Jan 29, 2019 at 04:43:33PM -0600, Bjorn Helgaas wrote:
> > > > > On Tue, Jan 22, 2019 at 01:02:54PM -0600, Bjorn Helgaas wrote:
> > > > > > From: Bjorn Helgaas <bhelgaas@google.com>
> > > > > >
> > > > > > pci_bridge_check_ranges() determines whether a bridge supports
> > > > > > the optional I/O and prefetchable memory windows and sets the
> > > > > > flag bits in the bridge resources.  This *could* be done once
> > > > > > during enumeration except that the resource allocation code
> > > > > > completely clears the flag bits, e.g., in the
> > > > > > pci_assign_unassigned_bridge_resources() path.
> > > > > >
> > > > > > The problem with pci_bridge_check_ranges() in the resource
> > > > > > allocation path is that we may allocate resources after devices
> > > > > > have been claimed by drivers, and pci_bridge_check_ranges()
> > > > > > *changes* the window registers to determine whether they're
> > > > > > writable.  This may break concurrent accesses to devices behind the
> > bridge.
> > > > > >
> > > > > > Add a new pci_read_bridge_windows() to determine whether a
> > > > > > bridge supports the optional windows, call it once during
> > > > > > enumeration, remember the results, and change
> > > > > > pci_bridge_check_ranges() so it doesn't touch the bridge windows but
> > sets the flag bits based on those remembered results.
> > > > > >
> > > > > > Link:
> > > > > > https://lore.kernel.org/linux-pci/1506151482-113560-1-git-send-e
> > > > > > mail-wangzhou1@hisilicon.com
> > > > > > Link:
> > > > > > https://lists.gnu.org/archive/html/qemu-devel/2018-12/msg02082.h
> > > > > > tml
> > > > > > Reported-by: xuyandong <xuyandong2@huawei.com>
> > > > > > Tested-by: xuyandong <xuyandong2@huawei.com>
> > > > > > Cc: Sagi Grimberg <sagi@grimberg.me>
> > > > > > Cc: Ofer Hayut <ofer@lightbitslabs.com>
> > > > > > Cc: Roy Shterman <roys@lightbitslabs.com>
> > > > > > Cc: Keith Busch <keith.busch@intel.com>
> > > > > > Cc: Zhou Wang <wangzhou1@hisilicon.com>
> > > > >
> > > > > Applied to pci/enumeration for v5.1.
> > > > >
> > > > > This is fairly simple in concept, but doesn't meet the letter of
> > > > > the restrictions in Documentation/process/stable-kernel-rules.rst,
> > > > > so I didn't tag it for stable.
> > > > >
> > > > > Is there a compelling argument to mark it for stable?
> > > >
> > > > Well it's needed downstream.
> > > > It's a bit above 100 lines with context. Is this what you mean?
> > >
> > > Yep, I should have been explicit about that.
> > >
> > > > If yes how about using my patch for stable as an alternative?
> > > > The rules allow for equivalent patches.
> > >
> > > Well, yes, that would be a possibility.
> > >
> > > I would rather develop an argument for marking *this* patch for
> > > stable.  Even though it is technically too large, I think we could
> > > make it work if we have compelling reasons.
> > >
> > > Those would need to be fleshed out a little more than "needed
> > > downstream" -- something about the scenarios where this happens, what
> > > the serious problem is, etc.
> > >
> > > The *ideal* thing would be to have an actual bugzilla.kernel.org
> > > report of the problem with a way to reproduce it and dmesg
> > > illustrating the problem.
> > 
> > xuyandong would you like to take a stub at creating the bugzilla entry?
> > If not let me know and I'll do it.
> > Thanks!
> > 
> Thanks, but I  do not want to create the bugzilla entry.

OK that's fair, you did quite a lot already.

Xuyandong thanks a lot for your contribution in reporting the problem,
proposing fixes and then testing patches, it is very much appreciated!


> 
> > 
> > > > > > ---
> > > > > >  drivers/pci/probe.c     |   52
> > +++++++++++++++++++++++++++++++++++++++++++++++
> > > > > >  drivers/pci/setup-bus.c |   45 ++++-------------------------------------
> > > > > >  include/linux/pci.h     |    3 +++
> > > > > >  3 files changed, 59 insertions(+), 41 deletions(-)
> > > > > >
> > > > > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c index
> > > > > > 257b9f6f2ebb..2ef8b954c65a 100644
> > > > > > --- a/drivers/pci/probe.c
> > > > > > +++ b/drivers/pci/probe.c
> > > > > > @@ -348,6 +348,57 @@ static void pci_read_bases(struct pci_dev *dev,
> > unsigned int howmany, int rom)
> > > > > >  	}
> > > > > >  }
> > > > > >
> > > > > > +static void pci_read_bridge_windows(struct pci_dev *bridge) {
> > > > > > +	u16 io;
> > > > > > +	u32 pmem, tmp;
> > > > > > +
> > > > > > +	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > > +	if (!io) {
> > > > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > > > +		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > > +		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > > > +	}
> > > > > > +	if (io)
> > > > > > +		bridge->io_window = 1;
> > > > > > +
> > > > > > +	/*
> > > > > > +	 * DECchip 21050 pass 2 errata: the bridge may miss an
> > address
> > > > > > +	 * disconnect boundary by one PCI data phase.  Workaround:
> > do not
> > > > > > +	 * use prefetching on this device.
> > > > > > +	 */
> > > > > > +	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device
> > == 0x0001)
> > > > > > +		return;
> > > > > > +
> > > > > > +	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > &pmem);
> > > > > > +	if (!pmem) {
> > > > > > +		pci_write_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE,
> > > > > > +					       0xffe0fff0);
> > > > > > +		pci_read_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE, &pmem);
> > > > > > +		pci_write_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE, 0x0);
> > > > > > +	}
> > > > > > +	if (!pmem)
> > > > > > +		return;
> > > > > > +
> > > > > > +	bridge->pref_window = 1;
> > > > > > +
> > > > > > +	if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > > > > +PCI_PREF_RANGE_TYPE_64) {
> > > > > > +
> > > > > > +		/*
> > > > > > +		 * Bridge claims to have a 64-bit prefetchable memory
> > > > > > +		 * window; verify that the upper bits are actually
> > > > > > +		 * writable.
> > > > > > +		 */
> > > > > > +		pci_read_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32, &pmem);
> > > > > > +		pci_write_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32,
> > > > > > +				       0xffffffff);
> > > > > > +		pci_read_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32, &tmp);
> > > > > > +		pci_write_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32, pmem);
> > > > > > +		if (tmp)
> > > > > > +			bridge->pref_64_window = 1;
> > > > > > +	}
> > > > > > +}
> > > > > > +
> > > > > >  static void pci_read_bridge_io(struct pci_bus *child)  {
> > > > > >  	struct pci_dev *dev = child->self; @@ -1739,6 +1790,7 @@ int
> > > > > > pci_setup_device(struct pci_dev *dev)
> > > > > >  		pci_read_irq(dev);
> > > > > >  		dev->transparent = ((dev->class & 0xff) == 1);
> > > > > >  		pci_read_bases(dev, 2, PCI_ROM_ADDRESS1);
> > > > > > +		pci_read_bridge_windows(dev);
> > > > > >  		set_pcie_hotplug_bridge(dev);
> > > > > >  		pos = pci_find_capability(dev, PCI_CAP_ID_SSVID);
> > > > > >  		if (pos) {
> > > > > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
> > > > > > index ed960436df5e..1941bb0a6c13 100644
> > > > > > --- a/drivers/pci/setup-bus.c
> > > > > > +++ b/drivers/pci/setup-bus.c
> > > > > > @@ -735,58 +735,21 @@ int pci_claim_bridge_resource(struct pci_dev
> > *bridge, int i)
> > > > > >     base/limit registers must be read-only and read as 0. */
> > > > > > static void pci_bridge_check_ranges(struct pci_bus *bus)  {
> > > > > > -	u16 io;
> > > > > > -	u32 pmem;
> > > > > >  	struct pci_dev *bridge = bus->self;
> > > > > > -	struct resource *b_res;
> > > > > > +	struct resource *b_res =
> > > > > > +&bridge->resource[PCI_BRIDGE_RESOURCES];
> > > > > >
> > > > > > -	b_res = &bridge->resource[PCI_BRIDGE_RESOURCES];
> > > > > >  	b_res[1].flags |= IORESOURCE_MEM;
> > > > > >
> > > > > > -	pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > > -	if (!io) {
> > > > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0xe0f0);
> > > > > > -		pci_read_config_word(bridge, PCI_IO_BASE, &io);
> > > > > > -		pci_write_config_word(bridge, PCI_IO_BASE, 0x0);
> > > > > > -	}
> > > > > > -	if (io)
> > > > > > +	if (bridge->io_window)
> > > > > >  		b_res[0].flags |= IORESOURCE_IO;
> > > > > >
> > > > > > -	/*  DECchip 21050 pass 2 errata: the bridge may miss an
> > address
> > > > > > -	    disconnect boundary by one PCI data phase.
> > > > > > -	    Workaround: do not use prefetching on this device. */
> > > > > > -	if (bridge->vendor == PCI_VENDOR_ID_DEC && bridge->device
> > == 0x0001)
> > > > > > -		return;
> > > > > > -
> > > > > > -	pci_read_config_dword(bridge, PCI_PREF_MEMORY_BASE,
> > &pmem);
> > > > > > -	if (!pmem) {
> > > > > > -		pci_write_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE,
> > > > > > -					       0xffe0fff0);
> > > > > > -		pci_read_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE, &pmem);
> > > > > > -		pci_write_config_dword(bridge,
> > PCI_PREF_MEMORY_BASE, 0x0);
> > > > > > -	}
> > > > > > -	if (pmem) {
> > > > > > +	if (bridge->pref_window) {
> > > > > >  		b_res[2].flags |= IORESOURCE_MEM |
> > IORESOURCE_PREFETCH;
> > > > > > -		if ((pmem & PCI_PREF_RANGE_TYPE_MASK) ==
> > > > > > -		    PCI_PREF_RANGE_TYPE_64) {
> > > > > > +		if (bridge->pref_64_window) {
> > > > > >  			b_res[2].flags |= IORESOURCE_MEM_64;
> > > > > >  			b_res[2].flags |= PCI_PREF_RANGE_TYPE_64;
> > > > > >  		}
> > > > > >  	}
> > > > > > -
> > > > > > -	/* double check if bridge does support 64 bit pref */
> > > > > > -	if (b_res[2].flags & IORESOURCE_MEM_64) {
> > > > > > -		u32 mem_base_hi, tmp;
> > > > > > -		pci_read_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32,
> > > > > > -					 &mem_base_hi);
> > > > > > -		pci_write_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32,
> > > > > > -					       0xffffffff);
> > > > > > -		pci_read_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32, &tmp);
> > > > > > -		if (!tmp)
> > > > > > -			b_res[2].flags &= ~IORESOURCE_MEM_64;
> > > > > > -		pci_write_config_dword(bridge,
> > PCI_PREF_BASE_UPPER32,
> > > > > > -				       mem_base_hi);
> > > > > > -	}
> > > > > >  }
> > > > > >
> > > > > >  /* Helper function for sizing routines: find first available
> > > > > > diff --git a/include/linux/pci.h b/include/linux/pci.h index
> > > > > > 65f1d8c2f082..40b327b814aa 100644
> > > > > > --- a/include/linux/pci.h
> > > > > > +++ b/include/linux/pci.h
> > > > > > @@ -373,6 +373,9 @@ struct pci_dev {
> > > > > >  	bool		match_driver;		/* Skip attaching
> > driver */
> > > > > >
> > > > > >  	unsigned int	transparent:1;		/* Subtractive decode
> > bridge */
> > > > > > +	unsigned int	io_window:1;		/* Bridge has I/O
> > window */
> > > > > > +	unsigned int	pref_window:1;		/* Bridge has pref
> > mem window */
> > > > > > +	unsigned int	pref_64_window:1;	/* Pref mem window
> > is 64-bit */
> > > > > >  	unsigned int	multifunction:1;	/* Multi-function device */
> > > > > >
> > > > > >  	unsigned int	is_busmaster:1;		/* Is busmaster */
> > > > > >