271 lines
8.5 KiB
Diff
271 lines
8.5 KiB
Diff
From b23853af6eb71e4c9b2e2d235b1db80541d33116 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Wed, 15 Nov 2017 18:01:00 +0100
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Subject: [PATCH 3/3] OvmfPkg: save on I/O port accesses when the debug port is
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not in use
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When SEV is enabled, every debug message printed by OVMF to the
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QEMU debug port traps from the guest to QEMU character by character
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because "REP OUTSB" cannot be used by IoWriteFifo8. Furthermore,
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when OVMF is built with the DEBUG_VERBOSE bit (value 0x00400000)
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enabled in "gEfiMdePkgTokenSpaceGuid.PcdDebugPrintErrorLevel", then the
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OvmfPkg/IoMmuDxe driver, and the OvmfPkg/Library/BaseMemEncryptSevLib
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library instance that is built into it, produce a huge amount of
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log messages. Therefore, in SEV guests, the boot time impact is huge
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(about 45 seconds _additional_ time spent writing to the debug port).
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While these messages are very useful for analyzing guest behavior,
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most of the time the user won't be capturing the OVMF debug log.
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In fact libvirt does not provide a method for configuring log capture;
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users that wish to do this (or are instructed to do this) have to resort
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to <qemu:arg>.
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The debug console device provides a handy detection mechanism; when read,
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it returns 0xE9 (which is very much unlike the 0xFF that is returned by
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an unused port). Use it to skip the possibly expensive OUT instructions
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when the debug I/O port isn't plugged anywhere.
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For SEC, the debug port has to be read before each full message.
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However:
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- if the debug port is available, then reading one byte before writing
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a full message isn't tragic, especially because SEC doesn't print many
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messages
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- if the debug port is not available, then reading one byte instead of
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writing a full message is still a win.
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Contributed-under: TianoCore Contribution Agreement 1.0
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Cc: Laszlo Ersek <lersek@redhat.com>
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Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
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Cc: Jordan Justen (Intel address) <jordan.l.justen@intel.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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---
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.../PlatformDebugLibIoPort/DebugLibDetect.h | 57 ++++++++++++++++++++++
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OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c | 28 +++++++++--
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.../PlatformDebugLibIoPort/DebugLibDetect.c | 30 ++++++++++--
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.../PlatformDebugLibIoPort/DebugLibDetectRom.c | 21 +++++++-
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4 files changed, 127 insertions(+), 9 deletions(-)
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create mode 100644 OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.h
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diff --git a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.h b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.h
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new file mode 100644
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index 0000000000..1f739b55d8
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--- /dev/null
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+++ b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.h
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@@ -0,0 +1,57 @@
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+/** @file
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+ Base Debug library instance for QEMU debug port.
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+ It uses PrintLib to send debug messages to a fixed I/O port.
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+
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+ Copyright (c) 2017, Red Hat, Inc.<BR>
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+ This program and the accompanying materials
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+ are licensed and made available under the terms and conditions of the BSD License
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+ which accompanies this distribution. The full text of the license may be found at
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+ http://opensource.org/licenses/bsd-license.php.
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+
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+ THE PROGRAM IS DISTRIBUTED UNDER THE BSD LICENSE ON AN "AS IS" BASIS,
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+ WITHOUT WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
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+
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+**/
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+
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+#ifndef __DEBUG_IO_PORT_DETECT_H__
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+#define __DEBUG_IO_PORT_DETECT_H__
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+
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+#include <Base.h>
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+
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+//
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+// The constant value that is read from the debug I/O port
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+//
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+#define BOCHS_DEBUG_PORT_MAGIC 0xE9
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+
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+
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+/**
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+ Helper function to return whether the virtual machine has a debug I/O port.
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+ PlatformDebugLibIoPortFound can call this function directly or cache the
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+ result.
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+
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+ @retval TRUE if the debug I/O port device was detected.
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+ @retval FALSE otherwise
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+
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+**/
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+BOOLEAN
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+EFIAPI
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+PlatformDebugLibIoPortDetect (
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+ VOID
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+ );
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+
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+/**
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+ Return whether the virtual machine has a debug I/O port. DebugLib.c
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+ calls this function instead of PlatformDebugLibIoPortDetect, to allow
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+ caching if possible.
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+
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+ @retval TRUE if the debug I/O port device was detected.
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+ @retval FALSE otherwise
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+
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+**/
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+BOOLEAN
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+EFIAPI
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+PlatformDebugLibIoPortFound (
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+ VOID
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+ );
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+
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+#endif
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diff --git a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c
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index 5a1c86f2c3..36cde54976 100644
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--- a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c
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+++ b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLib.c
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@@ -22,6 +22,7 @@
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#include <Library/PcdLib.h>
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#include <Library/BaseMemoryLib.h>
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#include <Library/DebugPrintErrorLevelLib.h>
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+#include "DebugLibDetect.h"
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//
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// Define the maximum debug and assert message length that this library supports
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@@ -61,9 +62,10 @@ DebugPrint (
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ASSERT (Format != NULL);
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//
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- // Check driver debug mask value and global mask
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+ // Check if the global mask disables this message or the device is inactive
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//
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- if ((ErrorLevel & GetDebugPrintErrorLevel ()) == 0) {
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+ if ((ErrorLevel & GetDebugPrintErrorLevel ()) == 0 ||
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+ !PlatformDebugLibIoPortFound ()) {
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return;
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}
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@@ -120,9 +122,11 @@ DebugAssert (
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FileName, (UINT64)LineNumber, Description);
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//
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- // Send the print string to the debug I/O port
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+ // Send the print string to the debug I/O port, if present
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//
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- IoWriteFifo8 (PcdGet16 (PcdDebugIoPort), Length, Buffer);
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+ if (PlatformDebugLibIoPortFound ()) {
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+ IoWriteFifo8 (PcdGet16 (PcdDebugIoPort), Length, Buffer);
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+ }
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//
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// Generate a Breakpoint, DeadLoop, or NOP based on PCD settings
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@@ -265,3 +269,19 @@ DebugPrintLevelEnabled (
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{
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return (BOOLEAN) ((ErrorLevel & PcdGet32(PcdFixedDebugPrintErrorLevel)) != 0);
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}
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+
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+/**
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+ Return the result of detecting the debug I/O port device.
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+
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+ @retval TRUE if the debug I/O port device was detected.
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+ @retval FALSE otherwise
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+
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+**/
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+BOOLEAN
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+EFIAPI
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+PlatformDebugLibIoPortDetect (
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+ VOID
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+ )
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+{
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+ return IoRead8 (PcdGet16 (PcdDebugIoPort)) == BOCHS_DEBUG_PORT_MAGIC;
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+}
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diff --git a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
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index bad054f286..81c44eece9 100644
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--- a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
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+++ b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetect.c
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@@ -1,6 +1,6 @@
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/** @file
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- Constructor code for QEMU debug port library.
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- Non-SEC instance.
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+ Detection code for QEMU debug port.
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+ Non-SEC instance, caches the result of detection.
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Copyright (c) 2017, Red Hat, Inc.<BR>
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This program and the accompanying materials
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@@ -14,9 +14,16 @@
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**/
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#include <Base.h>
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+#include "DebugLibDetect.h"
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+
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+//
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+// Set to TRUE if the debug I/O port is enabled
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+//
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+STATIC BOOLEAN mDebugIoPortFound = FALSE;
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/**
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- This constructor function does not have anything to do.
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+ This constructor function checks if the debug I/O port device is present,
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+ caching the result for later use.
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@retval RETURN_SUCCESS The constructor always returns RETURN_SUCCESS.
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@@ -27,5 +34,22 @@ PlatformDebugLibIoPortConstructor (
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VOID
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)
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{
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+ mDebugIoPortFound = PlatformDebugLibIoPortDetect();
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return RETURN_SUCCESS;
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}
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+
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+/**
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+ Return the cached result of detecting the debug I/O port device.
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+
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+ @retval TRUE if the debug I/O port device was detected.
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+ @retval FALSE otherwise
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+
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+**/
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+BOOLEAN
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+EFIAPI
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+PlatformDebugLibIoPortFound (
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+ VOID
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+ )
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+{
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+ return mDebugIoPortFound;
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+}
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diff --git a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetectRom.c b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetectRom.c
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index 83a118a0f7..b950919675 100644
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--- a/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetectRom.c
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+++ b/OvmfPkg/Library/PlatformDebugLibIoPort/DebugLibDetectRom.c
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@@ -1,6 +1,6 @@
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/** @file
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- Constructor code for QEMU debug port library.
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- SEC instance.
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+ Detection code for QEMU debug port.
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+ SEC instance, cannot cache the result of detection.
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Copyright (c) 2017, Red Hat, Inc.<BR>
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This program and the accompanying materials
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@@ -14,6 +14,7 @@
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**/
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#include <Base.h>
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+#include "DebugLibDetect.h"
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/**
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This constructor function does not have anything to do.
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@@ -29,3 +30,19 @@ PlatformRomDebugLibIoPortConstructor (
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{
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return RETURN_SUCCESS;
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}
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+
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+/**
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+ Return the result of detecting the debug I/O port device.
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+
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+ @retval TRUE if the debug I/O port device was detected.
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+ @retval FALSE otherwise
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+
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+**/
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+BOOLEAN
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+EFIAPI
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+PlatformDebugLibIoPortFound (
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+ VOID
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+ )
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+{
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+ return PlatformDebugLibIoPortDetect ();
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+}
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--
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2.14.3
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