edk2/0030-OvmfPkg-QemuFwCfgLib-rewrite-fw_cfg-probe.patch

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From 64d555122ee65151008255a30173a3608006ae25 Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Fri, 2 Dec 2022 14:10:08 +0100
Subject: [PATCH 30/32] OvmfPkg/QemuFwCfgLib: rewrite fw_cfg probe
Move the code to a new QemuFwCfgProbe() function. Use direct Io*() calls
instead of indirect QemuFwCfg*() calls to make sure we don't get
recursive calls. Also simplify CC guest detection.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Tested-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
(cherry picked from commit 81bbc1452c972218f071cd4a8f5899df974b1dae)
---
.../Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf | 1 -
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c | 101 +++++++-----------
2 files changed, 41 insertions(+), 61 deletions(-)
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
index 3910511880c9..1d7543a7d40f 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPeiLib.inf
@@ -41,7 +41,6 @@ [LibraryClasses]
DebugLib
IoLib
MemoryAllocationLib
- MemEncryptSevLib
[Pcd]
gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
index 7ab7027af168..a936fd103955 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
@@ -13,7 +13,6 @@
#include <Library/IoLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
-#include <Library/MemEncryptSevLib.h>
#include <WorkArea.h>
#include "QemuFwCfgLibInternal.h"
@@ -27,15 +26,16 @@ STATIC BOOLEAN mQemuFwCfgDmaSupported;
@retval TRUE It is Tdx guest
@retval FALSE It is not Tdx guest
**/
+STATIC
BOOLEAN
-QemuFwCfgIsTdxGuest (
+QemuFwCfgIsCcGuest (
VOID
)
{
CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER *CcWorkAreaHeader;
CcWorkAreaHeader = (CONFIDENTIAL_COMPUTING_WORK_AREA_HEADER *)FixedPcdGet32 (PcdOvmfWorkAreaBase);
- return (CcWorkAreaHeader != NULL && CcWorkAreaHeader->GuestType == CcGuestTypeIntelTdx);
+ return (CcWorkAreaHeader != NULL && CcWorkAreaHeader->GuestType != CcGuestTypeNonEncrypted);
}
/**
@@ -57,62 +57,49 @@ QemuFwCfgIsAvailable (
return InternalQemuFwCfgIsAvailable ();
}
+STATIC
+VOID
+QemuFwCfgProbe (
+ BOOLEAN *Supported,
+ BOOLEAN *DmaSupported
+ )
+{
+ UINT32 Signature;
+ UINT32 Revision;
+ BOOLEAN CcGuest;
+
+ // Use direct Io* calls for probing to avoid recursion.
+ IoWrite16 (FW_CFG_IO_SELECTOR, (UINT16)QemuFwCfgItemSignature);
+ IoReadFifo8 (FW_CFG_IO_DATA, sizeof Signature, &Signature);
+ IoWrite16 (FW_CFG_IO_SELECTOR, (UINT16)QemuFwCfgItemInterfaceVersion);
+ IoReadFifo8 (FW_CFG_IO_DATA, sizeof Revision, &Revision);
+ CcGuest = QemuFwCfgIsCcGuest ();
+
+ *Supported = FALSE;
+ *DmaSupported = FALSE;
+ if ((Signature == SIGNATURE_32 ('Q', 'E', 'M', 'U')) && (Revision >= 1)) {
+ *Supported = TRUE;
+ if ((Revision & FW_CFG_F_DMA) && !CcGuest) {
+ *DmaSupported = TRUE;
+ }
+ }
+
+ DEBUG ((
+ DEBUG_INFO,
+ "%a: Supported %d, DMA %d\n",
+ __func__,
+ *Supported,
+ *DmaSupported
+ ));
+}
+
RETURN_STATUS
EFIAPI
QemuFwCfgInitialize (
VOID
)
{
- UINT32 Signature;
- UINT32 Revision;
-
- //
- // Enable the access routines while probing to see if it is supported.
- // For probing we always use the IO Port (IoReadFifo8()) access method.
- //
- mQemuFwCfgSupported = TRUE;
- mQemuFwCfgDmaSupported = FALSE;
-
- QemuFwCfgSelectItem (QemuFwCfgItemSignature);
- Signature = QemuFwCfgRead32 ();
- DEBUG ((DEBUG_INFO, "FW CFG Signature: 0x%x\n", Signature));
- QemuFwCfgSelectItem (QemuFwCfgItemInterfaceVersion);
- Revision = QemuFwCfgRead32 ();
- DEBUG ((DEBUG_INFO, "FW CFG Revision: 0x%x\n", Revision));
- if ((Signature != SIGNATURE_32 ('Q', 'E', 'M', 'U')) ||
- (Revision < 1)
- )
- {
- DEBUG ((DEBUG_INFO, "QemuFwCfg interface not supported.\n"));
- mQemuFwCfgSupported = FALSE;
- return RETURN_SUCCESS;
- }
-
- if ((Revision & FW_CFG_F_DMA) == 0) {
- DEBUG ((DEBUG_INFO, "QemuFwCfg interface (IO Port) is supported.\n"));
- } else {
- //
- // If SEV is enabled then we do not support DMA operations in PEI phase.
- // This is mainly because DMA in SEV guest requires using bounce buffer
- // (which need to allocate dynamic memory and allocating a PAGE size'd
- // buffer can be challenge in PEI phase)
- //
- if (MemEncryptSevIsEnabled ()) {
- DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
- } else if (QemuFwCfgIsTdxGuest ()) {
- //
- // If TDX is enabled then we do not support DMA operations in PEI phase.
- // This is mainly because DMA in TDX guest requires using bounce buffer
- // (which need to allocate dynamic memory and allocating a PAGE size'd
- // buffer can be challenge in PEI phase)
- //
- DEBUG ((DEBUG_INFO, "TDX: QemuFwCfg fallback to IO Port interface.\n"));
- } else {
- mQemuFwCfgDmaSupported = TRUE;
- DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
- }
- }
-
+ QemuFwCfgProbe (&mQemuFwCfgSupported, &mQemuFwCfgDmaSupported);
return RETURN_SUCCESS;
}
@@ -183,17 +170,11 @@ InternalQemuFwCfgDmaBytes (
return;
}
- //
- // SEV does not support DMA operations in PEI stage, we should
- // not have reached here.
- //
- ASSERT (!MemEncryptSevIsEnabled ());
-
//
// TDX does not support DMA operations in PEI stage, we should
// not have reached here.
//
- ASSERT (!QemuFwCfgIsTdxGuest ());
+ ASSERT (!QemuFwCfgIsCcGuest ());
Access.Control = SwapBytes32 (Control);
Access.Length = SwapBytes32 (Size);
--
2.38.1