efi/libstub: Disable PCI DMA before grabbing the EFI memory map
Currently, the EFI stub will disable PCI DMA as the very last thing it does before calling ExitBootServices(), to avoid interfering with the firmware's normal operation as much as possible. However, the stub will invoke DisconnectController() on all endpoints downstream of the PCI bridges it disables, and this may affect the layout of the EFI memory map, making it substantially more likely that ExitBootServices() will fail the first time around, and that the EFI memory map needs to be reloaded. This, in turn, increases the likelihood that the slack space we allocated is insufficient (and we can no longer allocate memory via boot services after having called ExitBootServices() once), causing the second call to GetMemoryMap (and therefore the boot) to fail. This makes the PCI DMA disable feature a bit more fragile than it already is, so let's make it more robust, by allocating the space for the EFI memory map after disabling PCI DMA. Fixes: 4444f854 ("efi: Allow disabling PCI busmastering on bridges during boot") Reported-by:Glenn Washburn <development@efficientek.com> Acked-by:
Matthew Garrett <mjg59@srcf.ucam.org> Signed-off-by:
Ard Biesheuvel <ardb@kernel.org>
parent
d0a1865c
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