OvmfPkg/QemuFwCfgLib: Use BusMasterCommonBuffer to map FW_CFG_DMA_ACCESS
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:
committed by
Laszlo Ersek
parent
d0c9afea42
commit
f6c909ae5d
@@ -45,136 +45,6 @@ QemuFwCfgSelectItem (
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IoWrite16 (FW_CFG_IO_SELECTOR, (UINT16)(UINTN) QemuFwCfgItem);
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}
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/**
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Transfer an array of bytes, or skip a number of bytes, using the DMA
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interface.
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@param[in] Size Size in bytes to transfer or skip.
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@param[in,out] Buffer Buffer to read data into or write data from. Ignored,
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and may be NULL, if Size is zero, or Control is
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FW_CFG_DMA_CTL_SKIP.
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@param[in] Control One of the following:
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FW_CFG_DMA_CTL_WRITE - write to fw_cfg from Buffer.
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FW_CFG_DMA_CTL_READ - read from fw_cfg into Buffer.
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FW_CFG_DMA_CTL_SKIP - skip bytes in fw_cfg.
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**/
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VOID
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InternalQemuFwCfgDmaBytes (
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IN UINT32 Size,
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IN OUT VOID *Buffer OPTIONAL,
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IN UINT32 Control
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)
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{
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volatile FW_CFG_DMA_ACCESS LocalAccess;
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volatile FW_CFG_DMA_ACCESS *Access;
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UINT32 AccessHigh, AccessLow;
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UINT32 Status;
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UINT32 NumPages;
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VOID *DmaBuffer, *BounceBuffer;
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ASSERT (Control == FW_CFG_DMA_CTL_WRITE || Control == FW_CFG_DMA_CTL_READ ||
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Control == FW_CFG_DMA_CTL_SKIP);
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if (Size == 0) {
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return;
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}
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//
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// set NumPages to suppress incorrect compiler/analyzer warnings
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//
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NumPages = 0;
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//
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// When SEV is enabled then allocate DMA bounce buffer
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//
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if (InternalQemuFwCfgSevIsEnabled ()) {
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UINTN TotalSize;
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TotalSize = sizeof (*Access);
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//
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// Skip operation does not need buffer
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//
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if (Control != FW_CFG_DMA_CTL_SKIP) {
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TotalSize += Size;
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}
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//
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// Allocate SEV DMA buffer
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//
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NumPages = (UINT32)EFI_SIZE_TO_PAGES (TotalSize);
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InternalQemuFwCfgSevDmaAllocateBuffer (&BounceBuffer, NumPages);
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Access = BounceBuffer;
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DmaBuffer = (UINT8*)BounceBuffer + sizeof (*Access);
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//
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// Decrypt data from encrypted guest buffer into DMA buffer
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//
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if (Control == FW_CFG_DMA_CTL_WRITE) {
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CopyMem (DmaBuffer, Buffer, Size);
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}
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} else {
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Access = &LocalAccess;
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DmaBuffer = Buffer;
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BounceBuffer = NULL;
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}
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Access->Control = SwapBytes32 (Control);
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Access->Length = SwapBytes32 (Size);
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Access->Address = SwapBytes64 ((UINTN)DmaBuffer);
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//
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// Delimit the transfer from (a) modifications to Access, (b) in case of a
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// write, from writes to Buffer by the caller.
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//
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MemoryFence ();
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//
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// Start the transfer.
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//
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AccessHigh = (UINT32)RShiftU64 ((UINTN)Access, 32);
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AccessLow = (UINT32)(UINTN)Access;
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IoWrite32 (FW_CFG_IO_DMA_ADDRESS, SwapBytes32 (AccessHigh));
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IoWrite32 (FW_CFG_IO_DMA_ADDRESS + 4, SwapBytes32 (AccessLow));
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//
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// Don't look at Access.Control before starting the transfer.
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//
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MemoryFence ();
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//
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// Wait for the transfer to complete.
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//
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do {
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Status = SwapBytes32 (Access->Control);
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ASSERT ((Status & FW_CFG_DMA_CTL_ERROR) == 0);
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} while (Status != 0);
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//
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// After a read, the caller will want to use Buffer.
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//
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MemoryFence ();
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//
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// If Bounce buffer was allocated then copy the data into guest buffer and
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// free the bounce buffer
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//
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if (BounceBuffer != NULL) {
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//
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// Encrypt the data from DMA buffer into guest buffer
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//
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if (Control == FW_CFG_DMA_CTL_READ) {
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CopyMem (Buffer, DmaBuffer, Size);
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}
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InternalQemuFwCfgSevDmaFreeBuffer (BounceBuffer, NumPages);
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}
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}
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/**
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Reads firmware configuration bytes into a buffer
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