Clearing I/O port decoding in the PCI command register at ExitBootServices() breaks IDE boot in Windows, on QEMU's "pc" (i440fx) machine type. (AHCI boot on "q35" is unaffected.) Windows seems repeatedly stuck, apparently waiting for a timeout of sorts.
This is arguably a Windows bug; a native OS driver should not expect the firmware to leave the PCI command register in any particular state. Strictly speaking, we only need to disable BM-DMA at ExitBootServices(), in order to abort pending transfers to/from RAM, which is soon to be owned by the OS. BM-DMA is also the only bit that's explicitly named by the UEFI Driver Writers' Guide, for clearing at ExitBootServices(). I've verified that clearing only BM-DMA fixes the isse (boot time) on i440fx, and does not regress q35/AHCI. Cc: Aleksei Kovura <[email protected]> Cc: Ard Biesheuvel <[email protected]> Cc: Dann Frazier <[email protected]> Cc: Eric Dong <[email protected]> Cc: Star Zeng <[email protected]> Reported-by: Aleksei Kovura <[email protected]> Reported-by: Dann Frazier <[email protected]> Reported-by: https://launchpad.net/~cjkrupp Bisected-by: Dann Frazier <[email protected]> Bisected-by: https://launchpad.net/~cjkrupp Suggested-by: Ard Biesheuvel <[email protected]> Suggested-by: Star Zeng <[email protected]> Ref: https://bugs.launchpad.net/ubuntu/+source/edk2/+bug/1725560 Fixes: 6fb8ddd36bde45614b0a069528cdc97077835a74 Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Laszlo Ersek <[email protected]> --- Notes: Repo: https://github.com/lersek/edk2.git Branch: ata_disable_only_bmdma MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.h | 3 +-- MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c | 5 ++--- 2 files changed, 3 insertions(+), 5 deletions(-) diff --git a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.h b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.h index 8d6eac706c0b..92c5bf2001cd 100644 --- a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.h +++ b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.h @@ -123,8 +123,7 @@ typedef struct { LIST_ENTRY NonBlockingTaskList; // - // For disabling the device (especially Bus Master DMA) at - // ExitBootServices(). + // For disabling Bus Master DMA on the device at ExitBootServices(). // EFI_EVENT ExitBootEvent; } ATA_ATAPI_PASS_THRU_INSTANCE; diff --git a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c index 09064dda18b7..e10e0d4e65f6 100644 --- a/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c +++ b/MdeModulePkg/Bus/Ata/AtaAtapiPassThru/AtaAtapiPassThru.c @@ -480,8 +480,7 @@ InitializeAtaAtapiPassThru ( } /** - Disable the device (especially Bus Master DMA) when exiting the boot - services. + Disable Bus Master DMA on the device when exiting the boot services. @param[in] Event Event for which this notification function is being called. @@ -506,7 +505,7 @@ AtaPassThruExitBootServices ( PciIo->Attributes ( PciIo, EfiPciIoAttributeOperationDisable, - Instance->EnabledPciAttributes, + Instance->EnabledPciAttributes & EFI_PCI_IO_ATTRIBUTE_BUS_MASTER, NULL ); } -- 2.14.1.3.gb7cf6e02401b _______________________________________________ edk2-devel mailing list [email protected] https://lists.01.org/mailman/listinfo/edk2-devel
