On Wed, Mar 27, 2019 at 12:30 PM Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Mon, Mar 25, 2019 at 12:41:01PM +0100, 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.
> >
> > 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>
>
> Does this warrant a Fixes tag?
(digging in old sent email)
Fixes: 290c1fb358605402 ("PCI: rcar: Add MSI support for PCIe")
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
