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OvmfPkg/QemuFwCfgLib: Use BusMasterCommonBuffer to map FW_CFG_DMA_ACCESS

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Commit 09719a01b1 (OvmfPkg/QemuFwCfgLib: Implement SEV internal function
for Dxe phase) uses IOMMU protocol to allocate and free FW_CFG_DMA_ACCESS
buffer when SEV is active. During initial commits we made assumption that
IOMMU.AllocateBuffer() will provide PlainTextAddress (i.e C-bit cleared).
This assumption was wrong, the AllocateBuffer() protocol member is not
expected to produce a buffer that is immediatly usable, and client is
required to call Map() uncondtionally with BusMasterCommonBuffer[64] to
get a mapping which is accessable by both host and device.

The patch refactors code a bit and add the support to Map()
FW_CFG_DMA_ACCESS buffer using BusMasterCommonBuffer operation after
allocation and Unamp() before free.

The complete discussion about this and recommendation from Laszlo can be
found here [1]

[1] https://lists.01.org/pipermail/edk2-devel/2017-July/012652.html

Suggested-by: Laszlo Ersek <lersek@redhat.com>
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>
[lersek@redhat.com: convert pointers to UINTN before converting to UINT64]
[lersek@redhat.com: fix argument indentation in multi-line function call]
[lersek@redhat.com: explicitly compare pointers to NULL]
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Regression-tested-by: Laszlo Ersek <lersek@redhat.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
This commit is contained in:
Brijesh Singh
2017-08-02 18:12:48 -04:00
committed by Laszlo Ersek
parent d0c9afea42
commit f6c909ae5d
5 changed files with 373 additions and 298 deletions
Download Patch File Download Diff File Expand all files Collapse all files

109
OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgPei.c
View File

@@ -16,6 +16,7 @@
**/
#include <Library/BaseLib.h>
#include <Library/IoLib.h>
#include <Library/DebugLib.h>
#include <Library/QemuFwCfgLib.h>
#include <Library/MemEncryptSevLib.h>
@@ -85,7 +86,7 @@ QemuFwCfgInitialize (
// (which need to allocate dynamic memory and allocating a PAGE size'd
// buffer can be challenge in PEI phase)
//
if (InternalQemuFwCfgSevIsEnabled ()) {
if (MemEncryptSevIsEnabled ()) {
DEBUG ((DEBUG_INFO, "SEV: QemuFwCfg fallback to IO Port interface.\n"));
} else {
mQemuFwCfgDmaSupported = TRUE;
@@ -129,56 +130,78 @@ InternalQemuFwCfgDmaIsAvailable (
}
/**
Transfer an array of bytes, or skip a number of bytes, using the DMA
interface.
Returns a boolean indicating whether SEV is enabled
@param[in] Size Size in bytes to transfer or skip.
@retval TRUE SEV is enabled
@retval FALSE SEV is disabled
**/
BOOLEAN
InternalQemuFwCfgSevIsEnabled (
VOID
)
{
return MemEncryptSevIsEnabled ();
}
/**
Allocate a bounce buffer for SEV DMA.
@param[in] NumPage Number of pages.
@param[out] Buffer Allocated DMA Buffer pointer
@param[in,out] Buffer Buffer to read data into or write data from. Ignored,
and may be NULL, if Size is zero, or Control is
FW_CFG_DMA_CTL_SKIP.
@param[in] Control One of the following:
FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
FW_CFG_DMA_CTL_READ - read from fw_cfg into Buffer.
FW_CFG_DMA_CTL_SKIP - skip bytes in fw_cfg.
**/
VOID
InternalQemuFwCfgSevDmaAllocateBuffer (
OUT VOID **Buffer,
IN UINT32 NumPages
InternalQemuFwCfgDmaBytes (
IN UINT32 Size,
IN OUT VOID *Buffer OPTIONAL,
IN UINT32 Control
)
{
volatile FW_CFG_DMA_ACCESS Access;
UINT32 AccessHigh, AccessLow;
UINT32 Status;
ASSERT (Control == FW_CFG_DMA_CTL_WRITE || Control == FW_CFG_DMA_CTL_READ ||
Control == FW_CFG_DMA_CTL_SKIP);
if (Size == 0) {
return;
}
//
// We should never reach here
// SEV does not support DMA operations in PEI stage, we should
// not have reached here.
//
ASSERT (FALSE);
CpuDeadLoop ();
ASSERT (!MemEncryptSevIsEnabled ());
Access.Control = SwapBytes32 (Control);
Access.Length = SwapBytes32 (Size);
Access.Address = SwapBytes64 ((UINTN)Buffer);
//
// Delimit the transfer from (a) modifications to Access, (b) in case of a
// write, from writes to Buffer by the caller.
//
MemoryFence ();
//
// Start the transfer.
//
AccessHigh = (UINT32)RShiftU64 ((UINTN)&Access, 32);
AccessLow = (UINT32)(UINTN)&Access;
IoWrite32 (FW_CFG_IO_DMA_ADDRESS, SwapBytes32 (AccessHigh));
IoWrite32 (FW_CFG_IO_DMA_ADDRESS + 4, SwapBytes32 (AccessLow));
//
// Don't look at Access.Control before starting the transfer.
//
MemoryFence ();
//
// Wait for the transfer to complete.
//
do {
Status = SwapBytes32 (Access.Control);
ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);
} while (Status != 0);
//
// After a read, the caller will want to use Buffer.
//
MemoryFence ();
}
/**
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
)
{
//
// We should never reach here
//
ASSERT (FALSE);
CpuDeadLoop ();
}