When SEV is enabled, the DMA operations must be performed on a shared
(i.e unencrypted) pages. The patch adds SEV specific hooks to use the
bounce buffer when caller map/unmap host address to a DMA address and
similarly clears/set memory encryption attribute when caller allocates or
free the DMA pages.
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
---
OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c | 60 +++++++++++++++++++++++++++
OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf | 3 +
2 files changed, 61 insertions(+), 2 deletions(-)
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
index 0d960a8..39814cc 100644
--- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
@@ -25,6 +25,7 @@
#include <Library/MemoryAllocationLib.h>
#include <Library/UefiBootServicesTableLib.h>
#include <Library/BmDmaLib.h>
+#include <Library/MemEncryptSevLib.h>
#define FORCE_BELOW_4GB_TRUE TRUE
@@ -100,6 +101,15 @@ AllocateBounceBuffer (
}
//
+ // Clear C-bit on DMA pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevClearPageEncMask (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+ //
// If this is a read operation from the Bus Master's point of view,
// then copy the contents of the real buffer into the mapped buffer
// so the Bus Master can read the contents of the real buffer.
@@ -170,6 +180,23 @@ BmDmaMap (
PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
if (DmaAbove4GB || (PhysicalAddress + *NumberOfBytes) <= SIZE_4GB) {
+
+ //
+ // When SEV is enabled the DMA operation must be performed on shared pages. We force to use the
+ // bounce buffer path which will take care of allocating shared Dma buffers mapping
+ //
+ if (MemEncryptSevIsEnabled () &&
+ (Operation == DmaOperationBusMasterRead || Operation == DmaOperationBusMasterWrite)) {
+ return AllocateBounceBuffer (
+ FORCE_BELOW_4GB_FALSE,
+ Operation,
+ PhysicalAddress,
+ NumberOfBytes,
+ DeviceAddress,
+ Mapping
+ );
+ }
+
//
// If we CAN handle DMA above 4GB or the transfer is below 4GB,
// the DeviceAddress is simply the HostAddress
@@ -218,7 +245,8 @@ BmDmaUnmap (
IN VOID *Mapping
)
{
- MAP_INFO *MapInfo;
+ MAP_INFO *MapInfo;
+ EFI_STATUS Status;
//
// Check for invalid inputs
@@ -251,6 +279,17 @@ BmDmaUnmap (
}
//
+ // When SEV is enabled then Dma buffer allocate by bounce buffer have C-bit cleared,
+ // restore the C-bit before we release the resources
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevSetPageEncMask (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+
+ //
// Free the mapped buffer and the MAP_INFO structure.
//
gBS->FreePages (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
@@ -322,8 +361,15 @@ BmDmaAllocateBuffer (
);
if (!EFI_ERROR (Status)) {
*HostAddress = (VOID *) (UINTN) PhysicalAddress;
+ //
+ // Clear C-bit on Dma pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevClearPageEncMask (PhysicalAddress, Pages);
+ }
}
+
return Status;
}
@@ -346,6 +392,18 @@ BmDmaFreeBuffer (
IN UINTN Pages
)
{
+ EFI_STATUS Status;
+
+ //
+ // Restore the C-bit on DMA pages
+ //
+ if (MemEncryptSevIsEnabled ()) {
+ Status = MemEncryptSevSetPageEncMask ((UINTN) HostAddress, Pages);
+ if (Status != EFI_SUCCESS) {
+ return Status;
+ }
+ }
+
return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
}
diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
index 4ddb27d..fb97caa 100644
--- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
+++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
@@ -29,6 +29,7 @@
[Packages]
MdePkg/MdePkg.dec
MdeModulePkg/MdeModulePkg.dec
+ OvmfPkg/OvmfPkg.dec
[LibraryClasses]
BaseLib
@@ -37,5 +38,5 @@
DxeServicesTableLib
MemoryAllocationLib
UefiBootServicesTableLib
-
+ MemEncryptSevLib
_______________________________________________
edk2-devel mailing list
edk2-devel@lists.01.org
https://lists.01.org/mailman/listinfo/edk2-devel
On 03/21/17 22:13, Brijesh Singh wrote:
> When SEV is enabled, the DMA operations must be performed on a shared
> (i.e unencrypted) pages. The patch adds SEV specific hooks to use the
> bounce buffer when caller map/unmap host address to a DMA address and
> similarly clears/set memory encryption attribute when caller allocates or
> free the DMA pages.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
> ---
> OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c | 60 +++++++++++++++++++++++++++
> OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf | 3 +
> 2 files changed, 61 insertions(+), 2 deletions(-)
It looks like Leo's DxeBmDmaLib isn't final yet (based on the v4
feedback I can see on the list).
Can we perhaps modify the BmDmaLib library class (= public interface)
such that a client module (an executable or even another library) can
reuse the base instance of BmDmaLib, and only provide the hooks?
If not, I guess it's not a big deal, MdeModulePkg/Library/DxeBmDmaLib
contains about 10-12 KB of source. I figured I'd ask though.
Thanks,
Laszlo
>
> diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
> index 0d960a8..39814cc 100644
> --- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
> +++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.c
> @@ -25,6 +25,7 @@
> #include <Library/MemoryAllocationLib.h>
> #include <Library/UefiBootServicesTableLib.h>
> #include <Library/BmDmaLib.h>
> +#include <Library/MemEncryptSevLib.h>
>
>
> #define FORCE_BELOW_4GB_TRUE TRUE
> @@ -100,6 +101,15 @@ AllocateBounceBuffer (
> }
>
> //
> + // Clear C-bit on DMA pages
> + //
> + if (MemEncryptSevIsEnabled ()) {
> + Status = MemEncryptSevClearPageEncMask (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
> + if (Status != EFI_SUCCESS) {
> + return Status;
> + }
> + }
> + //
> // If this is a read operation from the Bus Master's point of view,
> // then copy the contents of the real buffer into the mapped buffer
> // so the Bus Master can read the contents of the real buffer.
> @@ -170,6 +180,23 @@ BmDmaMap (
>
> PhysicalAddress = (EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress;
> if (DmaAbove4GB || (PhysicalAddress + *NumberOfBytes) <= SIZE_4GB) {
> +
> + //
> + // When SEV is enabled the DMA operation must be performed on shared pages. We force to use the
> + // bounce buffer path which will take care of allocating shared Dma buffers mapping
> + //
> + if (MemEncryptSevIsEnabled () &&
> + (Operation == DmaOperationBusMasterRead || Operation == DmaOperationBusMasterWrite)) {
> + return AllocateBounceBuffer (
> + FORCE_BELOW_4GB_FALSE,
> + Operation,
> + PhysicalAddress,
> + NumberOfBytes,
> + DeviceAddress,
> + Mapping
> + );
> + }
> +
> //
> // If we CAN handle DMA above 4GB or the transfer is below 4GB,
> // the DeviceAddress is simply the HostAddress
> @@ -218,7 +245,8 @@ BmDmaUnmap (
> IN VOID *Mapping
> )
> {
> - MAP_INFO *MapInfo;
> + MAP_INFO *MapInfo;
> + EFI_STATUS Status;
>
> //
> // Check for invalid inputs
> @@ -251,6 +279,17 @@ BmDmaUnmap (
> }
>
> //
> + // When SEV is enabled then Dma buffer allocate by bounce buffer have C-bit cleared,
> + // restore the C-bit before we release the resources
> + //
> + if (MemEncryptSevIsEnabled ()) {
> + Status = MemEncryptSevSetPageEncMask (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
> + if (Status != EFI_SUCCESS) {
> + return Status;
> + }
> + }
> +
> + //
> // Free the mapped buffer and the MAP_INFO structure.
> //
> gBS->FreePages (MapInfo->MappedHostAddress, MapInfo->NumberOfPages);
> @@ -322,8 +361,15 @@ BmDmaAllocateBuffer (
> );
> if (!EFI_ERROR (Status)) {
> *HostAddress = (VOID *) (UINTN) PhysicalAddress;
> + //
> + // Clear C-bit on Dma pages
> + //
> + if (MemEncryptSevIsEnabled ()) {
> + Status = MemEncryptSevClearPageEncMask (PhysicalAddress, Pages);
> + }
> }
>
> +
> return Status;
> }
>
> @@ -346,6 +392,18 @@ BmDmaFreeBuffer (
> IN UINTN Pages
> )
> {
> + EFI_STATUS Status;
> +
> + //
> + // Restore the C-bit on DMA pages
> + //
> + if (MemEncryptSevIsEnabled ()) {
> + Status = MemEncryptSevSetPageEncMask ((UINTN) HostAddress, Pages);
> + if (Status != EFI_SUCCESS) {
> + return Status;
> + }
> + }
> +
> return gBS->FreePages ((EFI_PHYSICAL_ADDRESS) (UINTN) HostAddress, Pages);
> }
>
> diff --git a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
> index 4ddb27d..fb97caa 100644
> --- a/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
> +++ b/OvmfPkg/Library/DxeBmDmaLib/DxeBmDmaLib.inf
> @@ -29,6 +29,7 @@
> [Packages]
> MdePkg/MdePkg.dec
> MdeModulePkg/MdeModulePkg.dec
> + OvmfPkg/OvmfPkg.dec
>
> [LibraryClasses]
> BaseLib
> @@ -37,5 +38,5 @@
> DxeServicesTableLib
> MemoryAllocationLib
> UefiBootServicesTableLib
> -
> + MemEncryptSevLib
>
>
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
>
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