When SEV is enabled, the DMA must be performed on unencrypted pages.
So when get asked to perfom FWCFG DMA read or write, we allocate a
intermediate (bounce buffer) unencrypted buffer and use this buffer
for DMA read or write.
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf | 4 +
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c | 107 ++++++++++++++++++++
2 files changed, 111 insertions(+)
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
index 346bb881ffc1..f8df77f788b7 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
@@ -39,6 +39,7 @@ [Sources]
[Packages]
MdePkg/MdePkg.dec
+ MdeModulePkg/MdeModulePkg.dec
OvmfPkg/OvmfPkg.dec
[LibraryClasses]
@@ -47,4 +48,7 @@ [LibraryClasses]
DebugLib
IoLib
MemoryAllocationLib
+ MemEncryptSevLib
+[Protocols]
+ gEdkiiIoMmuProtocolGuid ## SOMETIMES_CONSUMES
diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
index ac05f4c347f3..059666ffa99b 100644
--- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
+++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
@@ -4,6 +4,7 @@
Copyright (C) 2013, Red Hat, Inc.
Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
+ Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
This program and the accompanying materials are licensed and made available
under the terms and conditions of the BSD License which accompanies this
@@ -14,14 +15,36 @@
WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
**/
+#include "Uefi.h"
+
+#include <Protocol/IoMmu.h>
+
+#include <Library/BaseLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
+#include <Library/UefiBootServicesTableLib.h>
+#include <Library/MemEncryptSevLib.h>
#include "QemuFwCfgLibInternal.h"
STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
STATIC BOOLEAN mQemuFwCfgDmaSupported;
+STATIC EDKII_IOMMU_PROTOCOL *mIoMmuProtocol;
+/**
+
+ Returns a boolean indicating whether SEV is enabled
+
+ @retval TRUE SEV is enabled
+ @retval FALSE SEV is disabled
+**/
+BOOLEAN
+InternalQemuFwCfgSevIsEnabled (
+ VOID
+ )
+{
+ return MemEncryptSevIsEnabled ();
+}
/**
Returns a boolean indicating if the firmware configuration interface
@@ -79,6 +102,21 @@ QemuFwCfgInitialize (
mQemuFwCfgDmaSupported = TRUE;
DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
}
+
+ //
+ // When SEV is enabled, the AmdSevDxe driver should have installed the IoMMU
+ // protocol which must be used for mapping host buffer to DMA buffer
+ //
+ if (mQemuFwCfgDmaSupported && MemEncryptSevIsEnabled ()) {
+ EFI_STATUS Status;
+
+ Status = gBS->LocateProtocol (&gEdkiiIoMmuProtocolGuid, NULL, (VOID **)&mIoMmuProtocol);
+ if (EFI_ERROR(Status)) {
+ DEBUG ((DEBUG_WARN, "QemuwCfgSevDma: failed to locate IoMmu protocol, disabling DMA support\n"));
+ mQemuFwCfgDmaSupported = FALSE;
+ }
+ }
+
return RETURN_SUCCESS;
}
@@ -114,3 +152,72 @@ InternalQemuFwCfgDmaIsAvailable (
{
return mQemuFwCfgDmaSupported;
}
+
+/**
+ Allocate a bounce buffer for SEV DMA.
+
+ @param[in] NumPage Number of pages.
+ @param[out] Buffer Allocated DMA Buffer pointer
+
+**/
+VOID
+InternalQemuFwCfgSevDmaAllocateBuffer (
+ IN UINT32 NumPages,
+ OUT VOID **Buffer
+ )
+{
+ EFI_STATUS Status;
+
+ if (!mIoMmuProtocol) {
+ //
+ // We should never reach here
+ //
+ ASSERT (FALSE);
+ CpuDeadLoop ();
+ }
+
+ Status = mIoMmuProtocol->AllocateBuffer (
+ mIoMmuProtocol,
+ 0,
+ EfiBootServicesData,
+ NumPages,
+ Buffer,
+ EDKII_IOMMU_ATTRIBUTE_MEMORY_CACHED
+ );
+ ASSERT_EFI_ERROR (Status);
+
+ DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma allocate buffer 0x%Lx Pages %d\n", (UINTN)Buffer, NumPages));
+
+}
+
+/**
+ Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
+
+ @param[in] NumPage Number of pages.
+ @param[in] Buffer DMA Buffer pointer
+
+**/
+VOID
+InternalQemuFwCfgSevDmaFreeBuffer (
+ IN VOID *Buffer,
+ IN UINT32 NumPages
+ )
+{
+ EFI_STATUS Status;
+
+ if (!mIoMmuProtocol) {
+ //
+ // We should never reach here
+ //
+ ASSERT (FALSE);
+ CpuDeadLoop ();
+ }
+
+ Status = mIoMmuProtocol->FreeBuffer (
+ mIoMmuProtocol,
+ NumPages,
+ Buffer
+ );
+ ASSERT_EFI_ERROR (Status);
+ DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma free buffer 0x%Lx Pages %d\n", (UINTN)Buffer, NumPages));
+}
--
2.7.4
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
comments below:
On 05/11/17 00:09, Brijesh Singh wrote:
> When SEV is enabled, the DMA must be performed on unencrypted pages.
> So when get asked to perfom FWCFG DMA read or write, we allocate a
> intermediate (bounce buffer) unencrypted buffer and use this buffer
> for DMA read or write.
>
>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf | 4 +
> OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c | 107 ++++++++++++++++++++
> 2 files changed, 111 insertions(+)
>
> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> index 346bb881ffc1..f8df77f788b7 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxeLib.inf
> @@ -39,6 +39,7 @@ [Sources]
>
> [Packages]
> MdePkg/MdePkg.dec
> + MdeModulePkg/MdeModulePkg.dec
> OvmfPkg/OvmfPkg.dec
>
> [LibraryClasses]
> @@ -47,4 +48,7 @@ [LibraryClasses]
> DebugLib
> IoLib
> MemoryAllocationLib
> + MemEncryptSevLib
>
> +[Protocols]
> + gEdkiiIoMmuProtocolGuid ## SOMETIMES_CONSUMES
> diff --git a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> index ac05f4c347f3..059666ffa99b 100644
> --- a/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> +++ b/OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgDxe.c
> @@ -4,6 +4,7 @@
>
> Copyright (C) 2013, Red Hat, Inc.
> Copyright (c) 2011 - 2013, Intel Corporation. All rights reserved.<BR>
> + Copyright (c) 2017, Advanced Micro Devices. All rights reserved.<BR>
>
> This program and the accompanying materials are licensed and made available
> under the terms and conditions of the BSD License which accompanies this
> @@ -14,14 +15,36 @@
> WARRANTIES OR REPRESENTATIONS OF ANY KIND, EITHER EXPRESS OR IMPLIED.
> **/
>
> +#include "Uefi.h"
(1) Not sure what this is needed for, but if it is needed, please use
<Uefi.h>.
> +
> +#include <Protocol/IoMmu.h>
> +
> +#include <Library/BaseLib.h>
> #include <Library/DebugLib.h>
> #include <Library/QemuFwCfgLib.h>
> +#include <Library/UefiBootServicesTableLib.h>
> +#include <Library/MemEncryptSevLib.h>
>
> #include "QemuFwCfgLibInternal.h"
>
> STATIC BOOLEAN mQemuFwCfgSupported = FALSE;
> STATIC BOOLEAN mQemuFwCfgDmaSupported;
>
> +STATIC EDKII_IOMMU_PROTOCOL *mIoMmuProtocol;
> +/**
> +
> + Returns a boolean indicating whether SEV is enabled
> +
> + @retval TRUE SEV is enabled
> + @retval FALSE SEV is disabled
> +**/
> +BOOLEAN
> +InternalQemuFwCfgSevIsEnabled (
> + VOID
> + )
> +{
> + return MemEncryptSevIsEnabled ();
> +}
>
> /**
> Returns a boolean indicating if the firmware configuration interface
> @@ -79,6 +102,21 @@ QemuFwCfgInitialize (
> mQemuFwCfgDmaSupported = TRUE;
> DEBUG ((DEBUG_INFO, "QemuFwCfg interface (DMA) is supported.\n"));
> }
> +
> + //
> + // When SEV is enabled, the AmdSevDxe driver should have installed the IoMMU
> + // protocol which must be used for mapping host buffer to DMA buffer
> + //
(2) The comment should be stronger. Please state that the IOMMU protocol
is guaranteed to be available, because the driver is listed in the
APRIORI DXE file.
> + if (mQemuFwCfgDmaSupported && MemEncryptSevIsEnabled ()) {
> + EFI_STATUS Status;
> +
> + Status = gBS->LocateProtocol (&gEdkiiIoMmuProtocolGuid, NULL, (VOID **)&mIoMmuProtocol);
> + if (EFI_ERROR(Status)) {
(3) Space missing before the paren.
> + DEBUG ((DEBUG_WARN, "QemuwCfgSevDma: failed to locate IoMmu protocol, disabling DMA support\n"));
> + mQemuFwCfgDmaSupported = FALSE;
> + }
> + }
> +
(4) Similarly to (2), this is too permissive. Please use DEBUG_ERROR,
ASSERT (FALSE), and CpuDeadLoop() here.
We must not silently degrade the fw_cfg interface to port-io, because
some client modules equate the presence of some fw_cfg files -- which
can also be found via port-io -- with DMA and fw_cfg write capability.
The expectation of those modules is correct, and we must not break it.
> return RETURN_SUCCESS;
> }
>
> @@ -114,3 +152,72 @@ InternalQemuFwCfgDmaIsAvailable (
> {
> return mQemuFwCfgDmaSupported;
> }
> +
> +/**
> + Allocate a bounce buffer for SEV DMA.
> +
> + @param[in] NumPage Number of pages.
> + @param[out] Buffer Allocated DMA Buffer pointer
> +
> +**/
> +VOID
> +InternalQemuFwCfgSevDmaAllocateBuffer (
> + IN UINT32 NumPages,
> + OUT VOID **Buffer
> + )
> +{
> + EFI_STATUS Status;
> +
> + if (!mIoMmuProtocol) {
> + //
> + // We should never reach here
> + //
> + ASSERT (FALSE);
> + CpuDeadLoop ();
> + }
(5) In turn, this can be replaced with
ASSERT (mIoMmuProtocol != NULL);
> +
> + Status = mIoMmuProtocol->AllocateBuffer (
> + mIoMmuProtocol,
> + 0,
> + EfiBootServicesData,
> + NumPages,
> + Buffer,
> + EDKII_IOMMU_ATTRIBUTE_MEMORY_CACHED
> + );
> + ASSERT_EFI_ERROR (Status);
(6) Please add a CpuDeadLoop() here.
> +
> + DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma allocate buffer 0x%Lx Pages %d\n", (UINTN)Buffer, NumPages));
> +
> +}
(7) Again I suggest to add gEfiCallerBaseName and __FUNCTION__ to the
debug message.
(8) Please also wrap it to 79 chars.
(9) %Lx is not right for printing a UINTN. There is no conversion
specifier that directly matches UINTN, so you'll have to use
(UINT64)(UINTN)Buffer
for portability between IA32 and X64.
(10) NumPages should be printed with %u or %x, it is unsigned.
> +
> +/**
> + Free the DMA buffer allocated using InternalQemuFwCfgSevDmaAllocateBuffer
> +
> + @param[in] NumPage Number of pages.
> + @param[in] Buffer DMA Buffer pointer
> +
> +**/
> +VOID
> +InternalQemuFwCfgSevDmaFreeBuffer (
> + IN VOID *Buffer,
> + IN UINT32 NumPages
> + )
> +{
> + EFI_STATUS Status;
> +
> + if (!mIoMmuProtocol) {
> + //
> + // We should never reach here
> + //
> + ASSERT (FALSE);
> + CpuDeadLoop ();
> + }
> +
> + Status = mIoMmuProtocol->FreeBuffer (
> + mIoMmuProtocol,
> + NumPages,
> + Buffer
> + );
> + ASSERT_EFI_ERROR (Status);
> + DEBUG ((DEBUG_VERBOSE, "QemuFwCfgSevDma free buffer 0x%Lx Pages %d\n", (UINTN)Buffer, NumPages));
> +}
>
The same comments apply here.
Thanks!
Laszlo
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
© 2016 - 2024 Red Hat, Inc.