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From: Bjorn Helgaas <bhelgaas@google.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>,
	Gavin Shan <shangw@linux.vnet.ibm.com>,
	xen-devel <xen-devel@lists.xensource.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
	"linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>
Subject: Re: [Xen-devel] [PATCH v4 18/22] xen/pci: Pay attention to PCI_MSIX_TABLE_OFFSET
Date: Fri, 26 Apr 2013 08:50:27 -0600	[thread overview]
Message-ID: <CAErSpo73yJcBU7Affd1qHhS_VVLnOS4msNfwrt-RaKhJce5Ngw@mail.gmail.com> (raw)
In-Reply-To: <517A45E602000078000D0F78@nat28.tlf.novell.com>

On Fri, Apr 26, 2013 at 1:16 AM, Jan Beulich <JBeulich@suse.com> wrote:
>>>> On 25.04.13 at 18:42, Bjorn Helgaas <bhelgaas@google.com> wrote:
>> On Thu, Apr 25, 2013 at 10:40:57AM +0100, Jan Beulich wrote:
>>> Recent hypervisors will actually
>>> only consume this to issue a warning if not matching what gets
>>> read from the corresponding BAR. Earlier hypervisors used this
>>> instead of reading the BAR.
>>
>> Note that pci_resource_start() gives you a CPU address, and what you
>> read from the BAR is a PCI bus address.  These are not in the same
>> address space and can't be directly compared.  I assume the
>> hypervisors take that into account and do the appropriate
>> conversions?
>
> I suppose Xen has never been run on a system where the two
> would differ, and it's quite likely that it would break on such
> systems. Question is - are there any x86-based systems where
> this is the case?

I haven't personally seen one, but it looks like they're coming, based
on this patch we merged last year:

commit b4873931cc8c934a9893d5962bde97aca23be983
Author: Mike Yoknis <mike.yoknis@hp.com>
Date:   Wed Nov 7 15:52:20 2012 -0700

    x86/PCI: Allow x86 platforms to use translation offsets

    The memory range descriptors in the _CRS control method contain an address
    translation offset for host bridges.  This value is used to translate
    addresses across the bridge.  The support to use _TRA values is present for
    other architectures but not for X86 platforms.

    For existing X86 platforms the _TRA value is zero.  Non-zero _TRA values
    are expected on future X86 platforms.  This change will register that value
    with the resource.

    Signed-off-by: Mike Yoknis <mike.yoknis@hp.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

  reply	other threads:[~2013-04-26 14:50 UTC|newest]

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-04-22 23:10 [PATCH v4 00/22] PCI: Cache MSI/MSI-X capability offsets, other cleanup Bjorn Helgaas
2013-04-22 23:10 ` [PATCH v4 01/22] [SCSI] megaraid_sas: Use correct #define for MSI-X capability Bjorn Helgaas
2013-04-22 23:52   ` Radford, Adam
2013-04-22 23:54   ` Fwd: " Bjorn Helgaas
2013-04-23  0:25     ` adam radford
2013-04-22 23:10 ` [PATCH v4 02/22] PCI: Use u8, not int, for PM capability offset Bjorn Helgaas
2013-04-22 23:32   ` Rafael J. Wysocki
2013-04-22 23:10 ` [PATCH v4 03/22] PCI: Cache MSI/MSI-X capability offsets in struct pci_dev Bjorn Helgaas
2013-04-22 23:10 ` [PATCH v4 04/22] PCI: Remove MSI/MSI-X cap check in pci_msi_check_device() Bjorn Helgaas
2013-04-22 23:10 ` [PATCH v4 05/22] PCI: Use cached MSI cap while enabling MSI interrupts Bjorn Helgaas
2013-04-22 23:10 ` [PATCH v4 06/22] PCI: Use cached MSI-X cap while enabling MSI-X Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 07/22] PCI: Clean up MSI/MSI-X capability #defines Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 08/22] PCI: Use cached MSI/MSI-X offsets from dev, not from msi_desc Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 09/22] PCI: Drop msi_control_reg() macro and use PCI_MSI_FLAGS directly Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 10/22] PCI: Drop msi_lower_address_reg() and msi_upper_address_reg() macros Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 11/22] PCI: Drop msi_data_reg() macro Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 12/22] PCI: Drop is_64bit_address() and is_mask_bit_support() macros Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 13/22] PCI: Drop msix_table_offset_reg() and msix_pba_offset_reg() macros Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 14/22] PCI: Use msix_table_size() directly, drop multi_msix_capable() Bjorn Helgaas
2013-04-22 23:11 ` [PATCH v4 15/22] PCI: Drop msi_mask_reg() and remove drivers/pci/msi.h Bjorn Helgaas
2013-04-22 23:12 ` [PATCH v4 16/22] PCI: Use PCI_MSIX_TABLE_BIR, not PCI_MSIX_FLAGS_BIRMASK Bjorn Helgaas
2013-04-22 23:12 ` [PATCH v4 17/22] PCI: Remove "extern" from function declarations Bjorn Helgaas
2013-04-22 23:12 ` [PATCH v4 18/22] xen/pci: Pay attention to PCI_MSIX_TABLE_OFFSET Bjorn Helgaas
2013-04-24 16:34   ` Bjorn Helgaas
2013-04-25  9:40     ` [Xen-devel] " Jan Beulich
2013-04-25  9:40       ` Jan Beulich
2013-04-25 16:42       ` Bjorn Helgaas
2013-04-26  7:16         ` Jan Beulich
2013-04-26  7:16           ` Jan Beulich
2013-04-26 14:50           ` Bjorn Helgaas [this message]
2013-04-22 23:12 ` [PATCH v4 19/22] xen/pci: Use PCI_MSIX_TABLE_BIR, not PCI_MSIX_FLAGS_BIRMASK Bjorn Helgaas
2013-04-24 16:35   ` Bjorn Helgaas
2013-04-22 23:12 ` [PATCH v4 20/22] xen/pci: Used cached MSI-X capability offset Bjorn Helgaas
2013-04-24 16:35   ` Bjorn Helgaas
2013-04-22 23:12 ` [PATCH v4 21/22] vfio-pci: Use PCI_MSIX_TABLE_BIR, not PCI_MSIX_FLAGS_BIRMASK Bjorn Helgaas
2013-04-23 20:12   ` Alex Williamson
2013-04-22 23:12 ` [PATCH v4 22/22] vfio-pci: Use cached MSI/MSI-X capabilities Bjorn Helgaas
2013-04-23 20:13   ` Alex Williamson
2013-04-24 17:48 ` [PATCH v4 00/22] PCI: Cache MSI/MSI-X capability offsets, other cleanup Bjorn Helgaas

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