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954b4b752a
The MSI message address in the RC address space can be 64 bit. The
R-Car PCIe RC supports such a 64bit MSI message address as well.
The code currently uses virt_to_phys(__get_free_pages()) to obtain
a reserved page for the MSI message address, and the return value
of which can be a 64 bit physical address on 64 bit system.
However, the driver only programs PCIEMSIALR register with the bottom
32 bits of the virt_to_phys(__get_free_pages()) return value and does
not program the top 32 bits into PCIEMSIAUR, but rather programs the
PCIEMSIAUR register with 0x0. This worked fine on older 32 bit R-Car
SoCs, however may fail on new 64 bit R-Car SoCs.
Since from a PCIe controller perspective, an inbound MSI is a memory
write to a special address (in case of this controller, defined by
the value in PCIEMSIAUR:PCIEMSIALR), which triggers an interrupt, but
never hits the DRAM _and_ because allocation of an MSI by a PCIe card
driver obtains the MSI message address by reading PCIEMSIAUR:PCIEMSIALR
in rcar_msi_setup_irqs(), incorrectly programmed PCIEMSIAUR cannot
cause memory corruption or other issues.
There is however the possibility that if virt_to_phys(__get_free_pages())
returned address above the 32bit boundary _and_ PCIEMSIAUR was programmed
to 0x0 _and_ if the system had physical RAM at the address matching the
value of PCIEMSIALR, a PCIe card driver could allocate a buffer with a
physical address matching the value of PCIEMSIALR and a remote write to
such a buffer by a PCIe card would trigger a spurious MSI.
Fixes:
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.