On Tue, Apr 02, 2019 at 03:33:07AM +0200, marek.vasut@xxxxxxxxx wrote: > From: Marek Vasut <marek.vasut+renesas@xxxxxxxxx> > > 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. Very good descripion! > Signed-off-by: Marek Vasut <marek.vasut+renesas@xxxxxxxxx> > Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> > Cc: Phil Edworthy <phil.edworthy@xxxxxxxxxxx> > Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx> > Cc: Wolfram Sang <wsa@xxxxxxxxxxxxx> > Cc: linux-renesas-soc@xxxxxxxxxxxxxxx > To: linux-pci@xxxxxxxxxxxxxxx > Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx> I double-checked with the datasheets previously. Reviewed-by: Wolfram Sang <wsa+renesas@xxxxxxxxxxxxxxxxxxxx>
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