From: Joel Fernandes <joelagn...@nvidia.com>
Instances of the Falcon microcontroller appear in modern Nvidia GPUs and
are crucial to the GPU boot process. Document some concepts which will
make nova-core boot code easier to digest. All the information is
derived from public sources such as public documents, OpenRM and Nouveau
code.
Signed-off-by: Joel Fernandes <joelagn...@nvidia.com>
Reviewed-by: Bagas Sanjaya <bagasdo...@gmail.com>
Signed-off-by: Alexandre Courbot <acour...@nvidia.com>
---
Documentation/gpu/nova/core/falcon.rst | 158 +++++++++++++++++++++++++++++++++
Documentation/gpu/nova/index.rst | 1 +
2 files changed, 159 insertions(+)
diff --git a/Documentation/gpu/nova/core/falcon.rst
b/Documentation/gpu/nova/core/falcon.rst
new file mode 100644
index
0000000000000000000000000000000000000000..33137082eb6c14cecda2fbe6fdb79e63ee9ca2e6
--- /dev/null
+++ b/Documentation/gpu/nova/core/falcon.rst
@@ -0,0 +1,158 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+Falcon (FAst Logic Controller)
+==============================
+The following sections describe the Falcon core and the ucode running on it.
+The descriptions are based on the Ampere GPU or earlier designs; however, they
+should mostly apply to future designs as well, but everything is subject to
+change. The overview provided here is mainly tailored towards understanding the
+interactions of nova-core driver with the Falcon.
+
+NVIDIA GPUs embed small RISC-like microcontrollers called Falcon cores, which
+handle secure firmware tasks, initialization, and power management. Modern
+NVIDIA GPUs may have multiple such Falcon instances (e.g., GSP (the GPU system
+processor) and SEC2 (the security engine)) and also may integrate a RISC-V
core.
+This core is capable of running both RISC-V and Falcon code.
+
+The code running on the Falcon cores is also called 'ucode', and will be
+referred to as such in the following sections.
+
+Falcons have separate instruction and data memories (IMEM/DMEM) and provide a
+small DMA engine (via the FBIF - "Frame Buffer Interface") to load code from
+system memory. The nova-core driver must reset and configure the Falcon, load
+its firmware via DMA, and start its CPU.
+
+Falcon security levels
+======================
+Falcons can run in Non-secure (NS), Light Secure (LS), or Heavy Secure (HS)
+modes.
+
+Heavy Secured (HS) also known as Privilege Level 3 (PL3)
+--------------------------------------------------------
+HS ucode is the most trusted code and has access to pretty much everything on
+the chip. The HS binary includes a signature in it which is verified at boot.
+This signature verification is done by the hardware itself, thus establishing a
+root of trust. For example, the FWSEC-FRTS command (see fwsec.rst) runs on the
+GSP in HS mode. FRTS, which involves setting up and loading content into the
WPR
+(Write Protect Region), has to be done by the HS ucode and cannot be done by
the
+host CPU or LS ucode.
+
+Light Secured (LS or PL2) and Non Secured (NS or PL0)
+-----------------------------------------------------
+These modes are less secure than HS. Like HS, the LS or NS ucode binary also
+typically includes a signature in it. To load firmware in LS or NS mode onto a
+Falcon, another Falcon needs to be running in HS mode, which also establishes
the
+root of trust. For example, in the case of an Ampere GPU, the CPU runs the
"Booter"
+ucode in HS mode on the SEC2 Falcon, which then authenticates and runs the
+run-time GSP binary (GSP-RM) in LS mode on the GSP Falcon. Similarly, as an
+example, after reset on an Ampere, FWSEC runs on the GSP which then loads the
+devinit engine onto the PMU in LS mode.
+
+Root of trust establishment
+---------------------------
+To establish a root of trust, the code running on a Falcon must be immutable
and
+hardwired into a read-only memory (ROM). This follows industry norms for
+verification of firmware. This code is called the Boot ROM (BROM). The
nova-core
+driver on the CPU communicates with Falcon's Boot ROM through various Falcon
+registers prefixed with "BROM" (see regs.rs).
+
+After nova-core driver reads the necessary ucode from VBIOS, it programs the
+BROM and DMA registers to trigger the Falcon to load the HS ucode from the
system
+memory into the Falcon's IMEM/DMEM. Once the HS ucode is loaded, it is verified
+by the Falcon's Boot ROM.
+
+Once the verified HS code is running on a Falcon, it can verify and load other
+LS/NS ucode binaries onto other Falcons and start them. The process of
signature
+verification is the same as HS; just in this case, the hardware (BROM) doesn't
+compute the signature, but the HS ucode does.
+
+The root of trust is therefore established as follows:
+ Hardware (Boot ROM running on the Falcon) -> HS ucode -> LS/NS ucode.
+
+On an Ampere GPU, for example, the boot verification flow is:
+ Hardware (Boot ROM running on the SEC2) ->
+ HS ucode (Booter running on the SEC2) ->
+ LS ucode (GSP-RM running on the GSP)
+
+.. note::
+ While the CPU can load HS ucode onto a Falcon microcontroller and have it
+ verified by the hardware and run, the CPU itself typically does not load
+ LS or NS ucode and run it. Loading of LS or NS ucode is done mainly by the
+ HS ucode. For example, on an Ampere GPU, after the Booter ucode runs on
the
+ SEC2 in HS mode and loads the GSP-RM binary onto the GSP, it needs to run
+ the "SEC2-RTOS" ucode at runtime. This presents a problem: there is no
+ component to load the SEC2-RTOS ucode onto the SEC2. The CPU cannot load
+ LS code, and GSP-RM must run in LS mode. To overcome this, the GSP is
+ temporarily made to run HS ucode (which is itself loaded by the CPU via
+ the nova-core driver using a "GSP-provided sequencer") which then loads
+ the SEC2-RTOS ucode onto the SEC2 in LS mode. The GSP then resumes
+ running its own GSP-RM LS ucode.
+
+Falcon memory subsystem and DMA engine
+======================================
+Falcons have separate instruction and data memories (IMEM/DMEM)
+and contains a small DMA engine called FBDMA (Framebuffer DMA) which does
+DMA transfers to/from the IMEM/DMEM memory inside the Falcon via the FBIF
+(Framebuffer Interface), to external memory.
+
+DMA transfers are possible from the Falcon's memory to both the system memory
+and the framebuffer memory (VRAM).
+
+To perform a DMA via the FBDMA, the FBIF is configured to decide how the memory
+is accessed (also known as aperture type). In the nova-core driver, this is
+determined by the `FalconFbifTarget` enum.
+
+The IO-PMP block (Input/Output Physical Memory Protection) unit in the Falcon
+controls access by the FBDMA to the external memory.
+
+Conceptual diagram (not exact) of the Falcon and its memory subsystem is as
follows::
+
+ External Memory (Framebuffer / System DRAM)
+ ^ |
+ | |
+ | v
+ +-----------------------------------------------------+
+ | | |
+ | +---------------+ | |
+ | | FBIF |-------+ | FALCON
+ | | (FrameBuffer | Memory Interface | PROCESSOR
+ | | InterFace) | |
+ | | Apertures | |
+ | | Configures | |
+ | | mem access | |
+ | +-------^-------+ |
+ | | |
+ | | FBDMA uses configured FBIF apertures |
+ | | to access External Memory
+ | |
+ | +-------v--------+ +---------------+
+ | | FBDMA | cfg | RISC |
+ | | (FrameBuffer |<---->| CORE |----->. Direct Core Access
+ | | DMA Engine) | | | |
+ | | - Master dev. | | (can run both | |
+ | +-------^--------+ | Falcon and | |
+ | | cfg--->| RISC-V code) | |
+ | | / | | |
+ | | | +---------------+ | +------------+
+ | | | | | BROM |
+ | | | <--->| (Boot ROM) |
+ | | / | +------------+
+ | | v |
+ | +---------------+ |
+ | | IO-PMP | Controls access by FBDMA |
+ | | (IO Physical | and other IO Masters |
+ | | Memory Protect) |
+ | +-------^-------+ |
+ | | |
+ | | Protected Access Path for FBDMA |
+ | v |
+ | +---------------------------------------+ |
+ | | Memory | |
+ | | +---------------+ +------------+ | |
+ | | | IMEM | | DMEM | |<-----+
+ | | | (Instruction | | (Data | |
+ | | | Memory) | | Memory) | |
+ | | +---------------+ +------------+ |
+ | +---------------------------------------+
+ +-----------------------------------------------------+
diff --git a/Documentation/gpu/nova/index.rst b/Documentation/gpu/nova/index.rst
index
e3650f53ff53113f31f63f67cf26116b5c070693..e39cb3163581ea4ff5b441b82e9efa4282c946f8
100644
--- a/Documentation/gpu/nova/index.rst
+++ b/Documentation/gpu/nova/index.rst
@@ -31,3 +31,4 @@ vGPU manager VFIO driver and the nova-drm driver.
core/vbios
core/devinit
core/fwsec
+ core/falcon
--
2.50.0
