On 11/28/18 20:16, Ard Biesheuvel wrote:
> The primary FV contains the firmware boot image, which is not
> runtime updatable in our case. So exposing it to the NOR flash
> driver is undesirable, since it may attempt to modify the NOR
> flash contents.
With you so far.
> It is also rather pointless, since we don't
> keep anything there that we don't already expose via the FVB
> protocol instances that DXE core creates for us based on the
> FV HOBs
I don't follow -- the DXE core does rely on the FV HOBs that we create for it,
but I don't remember the DXE core creating FVB protocol instances. An FVB
("firmware volume block") protocol instance is usually created by a flash
driver. What am I missing?
Do you mean handles with MemoryMapped(...)/FvFile(...) and Fv(...)/FvFile(...)
device paths on them? That point into firmware volumes (that have been
supposedly decompressed from flash to RAM)?
> (and so there is nothing the partition or file system
> drivers could potentially attach to via the block I/O and disk
> I/O protocol instances that the NOR flash driver creates)
Ugh, NorFlashDxe creates BlockIo and DiskIo interfaces itself???
Let's see...
/*
Although DiskIoDxe will automatically install the DiskIO protocol whenever
we install the BlockIO protocol, its implementation is sub-optimal as it reads
and writes entire blocks using the BlockIO protocol. In fact we can access
NOR flash with a finer granularity than that, so we can improve performance
by directly producing the DiskIO protocol.
*/
Umm... this flash driver does a lot more than I thought it did... or should. :)
Anyway I think it should suffice to say in the commit message that we don't
want to expose the first flash device as an FVB protocol instance, because (a)
it's read-only, and (b) in the DXE phase, we don't use anything from that flash
device. It contains:
- the reset vector,
- the SEC module,
- (for ArmVirtQemu) the non-compressed PEI core, and PEIMs,
- and a compressed bunch of DXE modules (incl. the DXE core) which are
decompressed to RAM anyway.
> So let's disregard the NOR flash block that covers the primary
> FV.
OK.
>
> Contributed-under: TianoCore Contribution Agreement 1.1
> Signed-off-by: Ard Biesheuvel <[email protected]>
> ---
> ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf | 5 +++++
> ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c | 13 +++++++++++--
> 2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
> b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
> index d86ff36dbd58..c5752a243e6b 100644
> --- a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
> +++ b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.inf
> @@ -28,6 +28,7 @@ [Sources.common]
> [Packages]
> MdePkg/MdePkg.dec
> ArmPlatformPkg/ArmPlatformPkg.dec
> + ArmPkg/ArmPkg.dec
> ArmVirtPkg/ArmVirtPkg.dec
>
> [LibraryClasses]
> @@ -40,3 +41,7 @@ [Protocols]
>
> [Depex]
> gFdtClientProtocolGuid
> +
> +[Pcd]
> + gArmTokenSpaceGuid.PcdFvBaseAddress
> + gArmTokenSpaceGuid.PcdFvSize
> diff --git a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
> b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
> index 2678f57eaaad..72b47bdb5a78 100644
> --- a/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
> +++ b/ArmVirtPkg/Library/NorFlashQemuLib/NorFlashQemuLib.c
> @@ -75,13 +75,22 @@ NorFlashPlatformGetDevices (
> Size = SwapBytes64 (ReadUnaligned64 ((VOID *)&Reg[2]));
> Reg += 4;
>
> + PropSize -= 4 * sizeof (UINT32);
> +
> + //
> + // Disregard any flash devices that overlap with the primary FV.
> + // The firmware is not updatable from inside the guest anyway.
> + //
> + if ((PcdGet64 (PcdFvBaseAddress) + PcdGet32 (PcdFvSize) >= Base) &&
> + (Base + Size) >= PcdGet64 (PcdFvBaseAddress)) {
> + continue;
> + }
> +
The overlap condition is expressed correctly, in general, I think; however,
both subconditions are off-by-one each. In each, we compare an exclusive limit
(one's end) with an inclusive limit (the other's base). And, when exclusive
equals inclusive, there is no overlap; they are directly adjacent only. I'd
drop the equal signs.
> mNorFlashDevices[Num].DeviceBaseAddress = (UINTN)Base;
> mNorFlashDevices[Num].RegionBaseAddress = (UINTN)Base;
> mNorFlashDevices[Num].Size = (UINTN)Size;
> mNorFlashDevices[Num].BlockSize = QEMU_NOR_BLOCK_SIZE;
> Num++;
> -
> - PropSize -= 4 * sizeof (UINT32);
> }
> }
>
>
Thanks
Laszlo
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