There's a small window between
- AllocFwCfgDmaAccessBuffer() mapping the new FW_CFG_DMA_ACCESS object for
common buffer operation (i.e., decrypting it), and
- InternalQemuFwCfgDmaBytes() setting the fields of the object.
In this window, earlier garbage in the object is "leaked" to the
hypervisor. So zero the object before we decrypt it.
(This commit message references AMD SEV directly, because QemuFwCfgDxeLib
is not *generally* enabled for IOMMU operation just yet, unlike our goal
for the virtio infrastructure. Instead, QemuFwCfgDxeLib uses
MemEncryptSevLib explicitly to detect SEV, and then relies on IOMMU
protocol behavior that is specific to SEV. At this point, this is by
design.)
Cc: Brijesh Singh <brijesh.singh@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Brijesh Singh <brijesh.singh@amd.com>
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>
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>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Current QemuFwCfgLib.inf is used in both Pei and Dxe phases. Add Pei
and Dxe inf file to provide a seperate QemuFwCfgLib instances for Pei
and Dxe phases.
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>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Laszlo Ersek
Brijesh Singh