Tianocore/edk2.git/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.h, branch master

OvmfPkg: Replace include guards with #pragma once

2026-02-23T21:01:28+00:00

Replace traditional `#ifndef`/`#define`/`#endif` include guards with `#pragma` once. `#pragma once` is a widely supported preprocessor directive that prevents header files from being included multiple times. It is supported by all toolchains used to build edk2: GCC, Clang/LLVM, and MSVC. Note: Headers taken directly from external projects, such as those in OvmfPkg/Include/IndustryStandard/Xen/ were not modified since they may be periodically re-synced and do not follow other edk2 coding stadards. Compared to macro-based include guards, `#pragma once`: - Eliminates the risk of macro name collisions or copy/paste errors where two headers inadvertently use the same guard macro. - Eliminate inconsistency in the way include guard macros are named (e.g., some files use `__FILE_H__`, others use `FILE_H_`, etc.). - Reduces boilerplate (three lines replaced by one). - Avoids polluting the macro namespace with guard symbols. - Can improve build times as the preprocessor can skip re-opening the file entirely, rather than re-reading it to find the matching `#endif` ("multiple-include optimization"). - Note that some compilers may already optimize traditional include guards, by recognzining the idiomatic pattern. This change is made acknowledging that overall portability of the code will technically be reduced, as `#pragma once` is not part of the C/C++ standards. However, this is considered acceptable given: 1. edk2 already defines a subset of supported compilers in BaseTools/Conf/tools_def.template, all of which have supported `#pragma once` for over two decades. 2. There have been concerns raised to the project about inconsistent include guard naming and potential macro collisions. Approximate compiler support dates: - MSVC: Supported since Visual C++ 4.2 (1996) - GCC: Supported since 3.4 (2004) (http://gnu.ist.utl.pt/software/gcc/gcc-3.4/changes.html) - Clang (LLVM based): Since initial release in 2007 Signed-off-by: Michael Kubacki

OvmfPkg/PlatformDebugLibIoPort: factor out debug port detection

2020-04-28T21:12:01+00:00

Factor out debug port detection in PlatformDebugLibIoPort. Signed-off-by: Anthony PERARD Message-Id: <20200423095358.2518197-4-anthony.perard@citrix.com> Reviewed-by: Philippe Mathieu-Daudé Reviewed-by: Laszlo Ersek

OvmfPkg/PlatformDebugLibIoPort: Reword QEMU to hypervisor

2020-04-28T21:12:01+00:00

We are going to reuse PlatformDebugLibIoPort to use debug IO port from hypervisors that aren't QEMU, so reword "QEMU" to "hypervisor" in the descriptions. Signed-off-by: Anthony PERARD Message-Id: <20200423095358.2518197-3-anthony.perard@citrix.com> Reviewed-by: Laszlo Ersek

OvmfPkg: Replace BSD License with BSD+Patent License

2019-04-09T17:58:19+00:00

https://bugzilla.tianocore.org/show_bug.cgi?id=1373 Replace BSD 2-Clause License with BSD+Patent License. This change is based on the following emails: https://lists.01.org/pipermail/edk2-devel/2019-February/036260.html https://lists.01.org/pipermail/edk2-devel/2018-October/030385.html RFCs with detailed process for the license change: V3: https://lists.01.org/pipermail/edk2-devel/2019-March/038116.html V2: https://lists.01.org/pipermail/edk2-devel/2019-March/037669.html V1: https://lists.01.org/pipermail/edk2-devel/2019-March/037500.html Contributed-under: TianoCore Contribution Agreement 1.1 Signed-off-by: Michael D Kinney Reviewed-by: Laszlo Ersek

OvmfPkg: save on I/O port accesses when the debug port is not in use

2017-11-17T17:35:12+00:00

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 . 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 Cc: Ard Biesheuvel Cc: Jordan Justen (Intel address) Signed-off-by: Paolo Bonzini Tested-by: Laszlo Ersek Reviewed-by: Laszlo Ersek