This is a note to let you know that I've just added the patch titled
efi/libstub: Disable PCI DMA before grabbing the EFI memory map
to the 6.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
efi-libstub-disable-pci-dma-before-grabbing-the-efi-.patch
and it can be found in the queue-6.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6038f59d2ebfc851efeb3ca7372ccf6a998f6a41
Author: Ard Biesheuvel <ardb@xxxxxxxxxx>
Date: Tue Jun 27 09:33:09 2023 +0200
efi/libstub: Disable PCI DMA before grabbing the EFI memory map
[ Upstream commit 2e28a798c3092ea42b968fa16ac835969d124898 ]
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: 4444f8541dad16fe ("efi: Allow disabling PCI busmastering on bridges during boot")
Reported-by: Glenn Washburn <development@xxxxxxxxxxxxxxx>
Acked-by: Matthew Garrett <mjg59@xxxxxxxxxxxxx>
Signed-off-by: Ard Biesheuvel <ardb@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 1e0203d74691f..732984295295f 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -378,6 +378,9 @@ efi_status_t efi_exit_boot_services(void *handle, void *priv,
struct efi_boot_memmap *map;
efi_status_t status;
+ if (efi_disable_pci_dma)
+ efi_pci_disable_bridge_busmaster();
+
status = efi_get_memory_map(&map, true);
if (status != EFI_SUCCESS)
return status;
@@ -388,9 +391,6 @@ efi_status_t efi_exit_boot_services(void *handle, void *priv,
return status;
}
- if (efi_disable_pci_dma)
- efi_pci_disable_bridge_busmaster();
-
status = efi_bs_call(exit_boot_services, handle, map->map_key);
if (status == EFI_INVALID_PARAMETER) {
