The DXE Core is one of those modules that call
ProcessLibraryConstructorList() manually.
Before DxeMain() [MdeModulePkg/Core/Dxe/DxeMain/DxeMain.c] calls
ProcessLibraryConstructorList(), and through it, our
PlatformDebugLibIoPortConstructor() function, DxeMain() invokes the
DEBUG() macro multiple times. That macro lands in our
PlatformDebugLibIoPortFound() function -- which currently relies on the
"mDebugIoPortFound" global variable that has (not yet) been set by the
constructor. As a result, early debug messages from the DXE Core are lost.
Move the device detection into PlatformDebugLibIoPortFound(), also caching
the fact (not just the result) of the device detection.
(We could introduce a separate DebugLib instance just for the DXE Core,
but the above approach works for all modules that currently consume the
PlatformDebugLibIoPort instance (which means "everything but SEC").)
This restores messages such as:
> CoreInitializeMemoryServices:
> BaseAddress - 0x7AF21000 Length - 0x3CDE000 MinimalMemorySizeNeeded - 0x10F4000
Keep the empty constructor function -- OVMF's DebugLib instances have
always had constructors; we had better not upset constructor dependency
ordering by making our instance(s) constructor-less.
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Fixes: c09d957130
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Tested-by: Brijesh Singh <brijesh.singh@amd.com>
[lersek@redhat.com: sanitize blank lines around "mDebugIoPortChecked"]
When SEV is enabled, every debug message printed by OVMF to the
QEMU debug port traps from the guest to QEMU character by character
because "REP OUTSB" cannot be used by IoWriteFifo8. Furthermore,
when OVMF is built with the DEBUG_VERBOSE bit (value 0x00400000)
enabled in "gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel", then the
OvmfPkg/IoMmuDxe driver, and the OvmfPkg/Library/BaseMemEncryptSevLib
library instance that is built into it, produce a huge amount of
log messages. Therefore, in SEV guests, the boot time impact is huge
(about 45 seconds _additional_ time spent writing to the debug port).
While these messages are very useful for analyzing guest behavior,
most of the time the user won't be capturing the OVMF debug log.
In fact libvirt does not provide a method for configuring log capture;
users that wish to do this (or are instructed to do this) have to resort
to <qemu:arg>.
The debug console device provides a handy detection mechanism; when read,
it returns 0xE9 (which is very much unlike the 0xFF that is returned by
an unused port). Use it to skip the possibly expensive OUT instructions
when the debug I/O port isn't plugged anywhere.
For SEC, the debug port has to be read before each full message.
However:
- if the debug port is available, then reading one byte before writing
a full message isn't tragic, especially because SEC doesn't print many
messages
- if the debug port is not available, then reading one byte instead of
writing a full message is still a win.
Contributed-under: TianoCore Contribution Agreement 1.0
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen (Intel address) <jordan.l.justen@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
The next patch will want to add a global variable to
PlatformDebugLibIoPort, but this is not suitable for the SEC
phase, because SEC runs from read-only flash. The solution is
to have two library instances, one for SEC and another
for all other firmware phases. This patch adds the "plumbing"
for the SEC library instance, separating the INF files and
moving the constructor to a separate C source file.
Contributed-under: TianoCore Contribution Agreement 1.1
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Jordan Justen (Intel address) <jordan.l.justen@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Tested-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Laszlo Ersek
Paolo Bonzini