On 09/29/14 14:30, Paolo Bonzini wrote: > Il 29/09/2014 14:07, Laszlo Ersek ha scritto: >> Apparently so, for 00:01.3 on the PIIX4. >> >> But for other PCI devices, I think it's writeable, isn't it? (Of course >> the devices-related code in this function should go away completely, if >> possible. git-blame is probably helpful here.) > > No, it's read-only. The PCI spec says so, and pci_init_wmask in QEMU's > hw/pci/pci.c agrees (in QEMU, PCI_INTERRUPT_LINE is 0x3c, and > PCI_INTERRUPT_PIN is 0x3d). > >>>> In fact, 0x3d should be _used_ to determine whether to fill in the >>>> register at 0x3c, and what value to write. OVMF must write there the >>>> GSI number associated to the corresponding INTX pin. See >>>> pci_bios_init_device in SeaBIOS's src/fw/pciinit.c. >> The PIIX4 spec says in 7.1.8. "INTLN—INTERRUPT LINE REGISTER (FUNCTION >> 3)" that "The value in this register has no affect on PIIX4 hardware >> operations." >> >> (It might still be useful for code that reads the register later, for >> all I know.) > > Exactly. The OS will usually use 0x3d together with the result of _PRT > to find the interrupt that is associated to a device; but the OS can > also rely on the firmware's setting of 0x3c, which is basically the same > thing but precomputed for non-ACPI-aware systems. > >>>> This should be done >>>> in a PEI (or is it PI?) driver, not DXE, because it must run on resume >>>> from S3. >> The place would be MiscInitialization() in >> "OvmfPkg/PlatformPei/Platform.c", but I'm not sure it would have any >> effect. (Its lack doesn't seem to.) > > Likely not, but still it's wrong and the current code doesn't make much > sense for Q35, so Gabriel may want to fix it anyway based on the Q35 DSDT.
Yes, please. :) Thanks, Laszlo ------------------------------------------------------------------------------ Slashdot TV. Videos for Nerds. Stuff that Matters. http://pubads.g.doubleclick.net/gampad/clk?id=160591471&iu=/4140/ostg.clktrk _______________________________________________ edk2-devel mailing list edk2-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/edk2-devel
