On Tue, Jun 04, 2024 at 02:27:54PM -0400, Rodrigo Vivi wrote:
> On Tue, Jun 04, 2024 at 07:16:18PM +0300, Imre Deak wrote:
> > From: Mika Westerberg <mika.westerb...@linux.intel.com>
> >
> > In typical cases PCIe tunneling is needed to make the devices fully
> > usable for the host system. However, it poses a security issue because
> > they can also use DMA to access the host memory. We already have two
> > ways of preventing this, one an IOMMU that is enabled on recent systems
> > by default and the second is the "authorized" attribute under each
> > connected device that needs to be written by userspace before a PCIe
> > tunnel is created. This option adds one more by adding a Kconfig option,
> > which is enabled by default, that can be used to make kernel binaries
> > where PCIe tunneling is completely disabled.
> >
> > Signed-off-by: Mika Westerberg <mika.westerb...@linux.intel.com>
> > References:
> > https://intel-gfx-ci.01.org/tree/drm-tip/Trybot_134314v1/bat-mtlp-9/boot0.txt
> > References: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/11261
> > Signed-off-by: Imre Deak <imre.d...@intel.com>
> > ---
> >
> > The issue at the first References: link is a known false-positive lockdep
> > issue
> > in the TBT/PCIe subsystem. After discussion with the TBT maintainer (Mika
> > Westerberg), the easiest solution for the iGFX CI is to disable the PCIe TBT
> > tunneling functionality which leads to the issue, as
> >
> > - It's not an important feature iGFX CI needs to test.
> > - There is no available solution (patch) yet to solve the lockdep issue.
> >
> > The feature could be re-enabled if needed once the lockdep issue is
> > solved upstream. This patch will be merged upstream, until that sending it
> > for core-for-CI.
>
> Acked-by: Rodrigo Vivi <rodrigo.v...@intel.com>
Thanks, this is merged now.
> > drivers/thunderbolt/Kconfig | 18 ++++++++++++++++++
> > drivers/thunderbolt/tb.c | 2 +-
> > drivers/thunderbolt/tb.h | 9 +++++++++
> > drivers/thunderbolt/tunnel.c | 8 ++++----
> > drivers/thunderbolt/usb4.c | 2 +-
> > 5 files changed, 33 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/thunderbolt/Kconfig b/drivers/thunderbolt/Kconfig
> > index 448fd2ec8f6e2..facf2e684c022 100644
> > --- a/drivers/thunderbolt/Kconfig
> > +++ b/drivers/thunderbolt/Kconfig
> > @@ -18,6 +18,24 @@ menuconfig USB4
> >
> > if USB4
> >
> > +config USB4_PCIE_TUNNELING
> > + bool "Allow PCI Express tunneling over USB4 fabric"
> > + depends on PCI
> > + default y
> > + help
> > + USB4 and Thunderbolt devices typically include PCIe switch
> > + with a number of PCIe endpoints such as USB host controllers,
> > + GPUs and network adapters. These are made available to the
> > + host system through PCIe tunneling. These can use DMA and
> > + therefore have access to the host memory which is typically
> > + guarded by an IOMMU. This option allows disabling PCIe
> > + tunneling completely.
> > +
> > + For devices to be usable it is recommended to say Y here.
> > +
> > + Note this only works with systems that use Software Based
> > + Connection Manager (this is most USB4 hosts).
> > +
> > config USB4_DEBUGFS_WRITE
> > bool "Enable write by debugfs to configuration spaces (DANGEROUS)"
> > help
> > diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
> > index 10e719dd837ce..7d71ff3f82c13 100644
> > --- a/drivers/thunderbolt/tb.c
> > +++ b/drivers/thunderbolt/tb.c
> > @@ -3181,7 +3181,7 @@ struct tb *tb_probe(struct tb_nhi *nhi)
> > if (!tb)
> > return NULL;
> >
> > - if (tb_acpi_may_tunnel_pcie())
> > + if (tb_may_tunnel_pcie())
> > tb->security_level = TB_SECURITY_USER;
> > else
> > tb->security_level = TB_SECURITY_NOPCIE;
> > diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
> > index 18aae4ccaed59..22fad8a9679ae 100644
> > --- a/drivers/thunderbolt/tb.h
> > +++ b/drivers/thunderbolt/tb.h
> > @@ -1436,6 +1436,15 @@ static inline int tb_acpi_power_on_retimers(struct
> > tb_port *port) { return 0; }
> > static inline int tb_acpi_power_off_retimers(struct tb_port *port) {
> > return 0; }
> > #endif
> >
> > +static inline bool tb_may_tunnel_pcie(void)
> > +{
> > +#ifdef CONFIG_USB4_PCIE_TUNNELING
> > + return tb_acpi_may_tunnel_pcie();
> > +#else
> > + return false;
> > +#endif
> > +}
> > +
> > #ifdef CONFIG_DEBUG_FS
> > void tb_debugfs_init(void);
> > void tb_debugfs_exit(void);
> > diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
> > index 41cf6378ad251..7c8397c135ba9 100644
> > --- a/drivers/thunderbolt/tunnel.c
> > +++ b/drivers/thunderbolt/tunnel.c
> > @@ -101,7 +101,7 @@ static unsigned int tb_available_credits(const struct
> > tb_port *port,
> > size_t ndp;
> >
> > usb3 = tb_acpi_may_tunnel_usb3() ? sw->max_usb3_credits : 0;
> > - pcie = tb_acpi_may_tunnel_pcie() ? sw->max_pcie_credits : 0;
> > + pcie = tb_may_tunnel_pcie() ? sw->max_pcie_credits : 0;
> >
> > if (tb_acpi_is_xdomain_allowed()) {
> > spare = min_not_zero(sw->max_dma_credits, dma_credits);
> > @@ -426,7 +426,7 @@ bool tb_tunnel_reserved_pci(struct tb_port *port, int
> > *reserved_up,
> > if (WARN_ON_ONCE(!port->remote))
> > return false;
> >
> > - if (!tb_acpi_may_tunnel_pcie())
> > + if (!tb_may_tunnel_pcie())
> > return false;
> >
> > if (tb_port_get_link_generation(port) < 4)
> > @@ -1510,7 +1510,7 @@ static unsigned int tb_dma_available_credits(const
> > struct tb_port *port)
> > int credits;
> >
> > credits = tb_available_credits(port, NULL);
> > - if (tb_acpi_may_tunnel_pcie())
> > + if (tb_may_tunnel_pcie())
> > credits -= sw->max_pcie_credits;
> > credits -= port->dma_credits;
> >
> > @@ -1821,7 +1821,7 @@ static int tb_usb3_consumed_bandwidth(struct
> > tb_tunnel *tunnel,
> > int *consumed_up, int *consumed_down)
> > {
> > struct tb_port *port = tb_upstream_port(tunnel->dst_port->sw);
> > - int pcie_weight = tb_acpi_may_tunnel_pcie() ? TB_PCI_WEIGHT : 0;
> > + int pcie_weight = tb_may_tunnel_pcie() ? TB_PCI_WEIGHT : 0;
> >
> > /*
> > * PCIe tunneling, if enabled, affects the USB3 bandwidth so
> > diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
> > index de480bf2a53de..cacc7bec19eb4 100644
> > --- a/drivers/thunderbolt/usb4.c
> > +++ b/drivers/thunderbolt/usb4.c
> > @@ -282,7 +282,7 @@ int usb4_switch_setup(struct tb_switch *sw)
> > * Only enable PCIe tunneling if the parent router supports it
> > * and it is not disabled.
> > */
> > - if (tb_acpi_may_tunnel_pcie() &&
> > + if (tb_may_tunnel_pcie() &&
> > tb_switch_find_port(parent, TB_TYPE_PCIE_DOWN)) {
> > val |= ROUTER_CS_5_PTO;
> > /*
> > --
> > 2.43.3
> >
