From: Yongji Xie <xyjxie@linux.vnet.ibm.com>
To: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pci@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
linux-doc@vger.kernel.org
Cc: bhelgaas@google.com, corbet@lwn.net, aik@ozlabs.ru,
alex.williamson@redhat.com, benh@kernel.crashing.org,
paulus@samba.org, mpe@ellerman.id.au, warrier@linux.vnet.ibm.com,
zhong@linux.vnet.ibm.com, nikunj@linux.vnet.ibm.com,
David Laight <David.Laight@ACULAB.COM>
Subject: Re: [RFC PATCH v3 0/5] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table on PPC64 platform
Date: Thu, 28 Jan 2016 18:01:51 +0800 [thread overview]
Message-ID: <56A9E70F.9030503@linux.vnet.ibm.com> (raw)
In-Reply-To: <1452841574-2781-1-git-send-email-xyjxie@linux.vnet.ibm.com>
Ping...
Alex, any comment?
Regards,
Yongji Xie
On 2016/1/15 15:06, Yongji Xie wrote:
> Current vfio-pci implementation disallows to mmap
> sub-page(size < PAGE_SIZE) MMIO BARs and MSI-X table. This is because
> sub-page BARs' mmio page may be shared with other BARs and MSI-X table
> should not be accessed directly from the guest for security reasons.
>
> But these will easily cause some performance issues for mmio accesses
> in guest when vfio passthrough sub-page BARs or BARs containing MSI-X
> table on PPC64 platform. This is because PAGE_SIZE is 64KB by default
> on PPC64 platform and the big page may easily hit the sub-page MMIO
> BARs' unmmapping and cause the unmmaping of the mmio page which
> MSI-X table locate in, which lead to mmio emulation in host.
>
> For sub-page MMIO BARs' unmmapping, this patchset adds a kernel
> parameter for PCI resource allocator to enforce the alignment of all
> MMIO BARs to be at least PAGE_SZIE and make it enabled by default on
> PPC64 platform so that sub-page BAR's mmio page will not be shared
> with other BARs. Then we can mmap sub-page MMIO BARs in vfio-pci driver
> with this parameter enabled.
>
> For MSI-X table's unmmapping, we think MSI-X table is safe to access
> directly from userspace if PCI host bridge support filtering of MSIs
> which can ensure that a given pci device can only shoot the MSIs
> assigned for it. So we add a pci_host_bridge attribute to indicate
> if this PCI host bridge supports filtering of MSIs. Then we can mmap
> MSI-X table with this attribute set.
>
> With this patchset applied, we can get almost 100% improvement on
> performance for mmio accesses when we passthrough sub-page BARs to guest
> in our test.
>
> The two vfio related patches(patch 2 and patch 5) are based on the
> proposed patchset[1].
>
> Changelog v3:
> - Rebase on new linux kernel mainline with the patchset[1] applied.
> - Add a function to check whether PCI BARs'mmio page is shared with
> other BARs.
> - Add a host bridge attribute to indicate PCI host bridge support
> filtering of MSIs.
> - Use the new host bridge attribute to check if MSI-X table can
> be mmapped instead of CONFIG_EEH.
> - Remove Kconfig option VFIO_PCI_MMAP_MSIX
>
> Changelog v2:
> - Rebase on v4.4-rc6 with the patchset[1] applied.
> - Use kernel parameter to enforce all MMIO BARs to be page aligned
> on PCI core code instead of doing it on PPC64 arch code.
> - Remove flags: VFIO_DEVICE_FLAGS_PCI_PAGE_ALIGNED
> VFIO_DEVICE_FLAGS_PCI_MSIX_MMAP
> - Add a Kconfig option to support for mmapping MSI-X table.
>
> [1] https://lkml.org/lkml/2015/11/23/748
>
> Yongji Xie (5):
> PCI: Add support for enforcing all MMIO BARs to be page aligned
> vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive
> PCI: Add host bridge attribute to indicate filtering of MSIs is supported
> powerpc/powernv/pci-ioda: Enable msi_filtered bit for any IODA host bridge
> vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs
>
> Documentation/kernel-parameters.txt | 5 +++++
> arch/powerpc/include/asm/pci.h | 11 +++++++++
> arch/powerpc/platforms/powernv/pci-ioda.c | 6 +++++
> drivers/pci/host-bridge.c | 6 +++++
> drivers/pci/pci.c | 35 +++++++++++++++++++++++++++++
> drivers/pci/pci.h | 8 ++++++-
> drivers/vfio/pci/vfio_pci.c | 13 ++++++++---
> include/linux/pci.h | 7 ++++++
> 8 files changed, 87 insertions(+), 4 deletions(-)
>
prev parent reply other threads:[~2016-01-28 10:02 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 7:06 [RFC PATCH v3 0/5] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table on PPC64 platform Yongji Xie
2016-01-15 7:06 ` [RFC PATCH v3 1/5] PCI: Add support for enforcing all MMIO BARs to be page aligned Yongji Xie
2016-01-28 22:46 ` Alex Williamson
2016-01-29 10:37 ` Yongji Xie
2016-01-29 19:01 ` Alex Williamson
2016-02-01 8:50 ` Yongji Xie
2016-01-15 7:06 ` [RFC PATCH v3 2/5] vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive Yongji Xie
2016-01-15 7:06 ` [RFC PATCH v3 3/5] PCI: Add host bridge attribute to indicate filtering of MSIs is supported Yongji Xie
2016-01-15 17:24 ` David Laight
2016-01-20 9:41 ` Yongji Xie
2016-01-28 22:46 ` Alex Williamson
2016-01-29 10:40 ` Yongji Xie
2016-01-29 19:05 ` Alex Williamson
2016-02-01 9:13 ` Yongji Xie
2016-01-15 7:06 ` [RFC PATCH v3 4/5] powerpc/powernv/pci-ioda: Enable msi_filtered bit for any IODA host bridge Yongji Xie
2016-01-15 7:06 ` [RFC PATCH v3 5/5] vfio-pci: Allow to mmap MSI-X table if host bridge supports filtering of MSIs Yongji Xie
2016-01-28 22:46 ` Alex Williamson
2016-01-29 10:42 ` Yongji Xie
2016-01-28 10:01 ` Yongji Xie [this message]
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