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Date: Tue, 29 Jan 2019 17:47:32 -0500
From: "Michael S. Tsirkin" <mst@...hat.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: linux-pci@...r.kernel.org, xuyandong <xuyandong2@...wei.com>,
Yinghai Lu <yinghai@...nel.org>,
Jesse Barnes <jbarnes@...tuousgeek.org>,
Sagi Grimberg <sagi@...mberg.me>,
Ofer Hayut <ofer@...htbitslabs.com>,
Roy Shterman <roys@...htbitslabs.com>,
Keith Busch <keith.busch@...el.com>,
"Wangzhou (B)" <wangzhou1@...ilicon.com>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI: Probe bridge window attributes once at
enumeration-time
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@...gle.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@...wei.com>
> > Tested-by: xuyandong <xuyandong2@...wei.com>
> > Cc: Sagi Grimberg <sagi@...mberg.me>
> > Cc: Ofer Hayut <ofer@...htbitslabs.com>
> > Cc: Roy Shterman <roys@...htbitslabs.com>
> > Cc: Keith Busch <keith.busch@...el.com>
> > Cc: Zhou Wang <wangzhou1@...ilicon.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 */
> >
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