[PATCH v2 0/9] gpu: nova-core: gsp: add continuation record support

[PATCH v2 0/9] gpu: nova-core: gsp: add continuation record support

[Eliot Courtney]

GSP commands over 16 pages need to be sent using "continuation records"
which essentially means splitting the payload over multiple commands.

This series adds a command type `ContinuationRecord` which just writes
its header and whatever payload it is given. It also adds types
`SplitState` and `SplitCommand` which support splitting a large RPC
into smaller ones while transparently letting regular sized RPCs be sent
without extra copies.

The send pathway uses `SplitState` to send all commands, but if
the command fits into 16 pages, it still writes directly into the
command queue. If it is larger than 16 pages and needs continuation
records, it writes into a staging buffer, so there is one copy.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
Changes in v2:
- Added doccoments
- Renamed driver_bytes_available_to_write to driver_write_area_size
- allocate_command_with_timeout merged allocate_command with timeout parameter
- Replaced hardcoded GSP_PAGE_SIZE * 16 with bindings
- Changed oversized command error from EIO to EMSGSIZE
- Added EMSGSIZE to kernel/error.rs
- Split WrappingCommand functionality into SplitState + SplitCommand enum
- Made max_size a const (MAX_CMD_SIZE)
- Removed send_continuation_record + added comment for type inference
- send_single_command now consumes the command
- Extracted command_size + used in SplitState 
- Link to v1: https://lore.kernel.org/r/20260212-cmdq-continuation-v1-0-73079ded55e6@nvidia.com

---
Eliot Courtney (9):
      gpu: nova-core: gsp: sort MsgFunction variants alphabetically
      gpu: nova-core: gsp: add mechanism to wait for space on command queue
      rust: add EMSGSIZE error code
      gpu: nova-core: gsp: add checking oversized commands
      gpu: nova-core: gsp: clarify invariant on command queue
      gpu: nova-core: gsp: unconditionally call variable payload handling
      gpu: nova-core: gsp: add command_size helper
      gpu: nova-core: gsp: support large RPCs via continuation record
      gpu: nova-core: gsp: add tests for SplitState

 drivers/gpu/nova-core/gsp/cmdq.rs                 | 118 +++++++---
 drivers/gpu/nova-core/gsp/commands.rs             | 256 +++++++++++++++++++++-
 drivers/gpu/nova-core/gsp/fw.rs                   | 106 +++++----
 drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs |   1 +
 rust/kernel/error.rs                              |   1 +
 5 files changed, 408 insertions(+), 74 deletions(-)
---
base-commit: 956b9cbd7f156c8672dac94a00de3c6a0939c692
change-id: 20260203-cmdq-continuation-b99f3d5966c3

Best regards,
-- 
Eliot Courtney <ecourtney@nvidia.com>

[PATCH v2 1/9] gpu: nova-core: gsp: sort MsgFunction variants alphabetically

[Eliot Courtney]

There is no particular order required here and keeping them alphabetical
will help preventing future mistakes.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/fw.rs | 97 +++++++++++++++++++++--------------------
 1 file changed, 50 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 83ff91614e36..5b96f5e622a4 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -192,34 +192,34 @@ pub(crate) fn new(gsp_firmware: &GspFirmware, fb_layout: &FbLayout) -> Self {
 #[repr(u32)]
 pub(crate) enum MsgFunction {
     // Common function codes
-    Nop = bindings::NV_VGPU_MSG_FUNCTION_NOP,
-    SetGuestSystemInfo = bindings::NV_VGPU_MSG_FUNCTION_SET_GUEST_SYSTEM_INFO,
-    AllocRoot = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT,
+    AllocChannelDma = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CHANNEL_DMA,
+    AllocCtxDma = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CTX_DMA,
     AllocDevice = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_DEVICE,
     AllocMemory = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_MEMORY,
-    AllocCtxDma = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CTX_DMA,
-    AllocChannelDma = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CHANNEL_DMA,
-    MapMemory = bindings::NV_VGPU_MSG_FUNCTION_MAP_MEMORY,
-    BindCtxDma = bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA,
     AllocObject = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_OBJECT,
+    AllocRoot = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT,
+    BindCtxDma = bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA,
     Free = bindings::NV_VGPU_MSG_FUNCTION_FREE,
-    Log = bindings::NV_VGPU_MSG_FUNCTION_LOG,
     GetGspStaticInfo = bindings::NV_VGPU_MSG_FUNCTION_GET_GSP_STATIC_INFO,
-    SetRegistry = bindings::NV_VGPU_MSG_FUNCTION_SET_REGISTRY,
-    GspSetSystemInfo = bindings::NV_VGPU_MSG_FUNCTION_GSP_SET_SYSTEM_INFO,
+    GetStaticInfo = bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO,
     GspInitPostObjGpu = bindings::NV_VGPU_MSG_FUNCTION_GSP_INIT_POST_OBJGPU,
     GspRmControl = bindings::NV_VGPU_MSG_FUNCTION_GSP_RM_CONTROL,
-    GetStaticInfo = bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO,
+    GspSetSystemInfo = bindings::NV_VGPU_MSG_FUNCTION_GSP_SET_SYSTEM_INFO,
+    Log = bindings::NV_VGPU_MSG_FUNCTION_LOG,
+    MapMemory = bindings::NV_VGPU_MSG_FUNCTION_MAP_MEMORY,
+    Nop = bindings::NV_VGPU_MSG_FUNCTION_NOP,
+    SetGuestSystemInfo = bindings::NV_VGPU_MSG_FUNCTION_SET_GUEST_SYSTEM_INFO,
+    SetRegistry = bindings::NV_VGPU_MSG_FUNCTION_SET_REGISTRY,
 
     // Event codes
     GspInitDone = bindings::NV_VGPU_MSG_EVENT_GSP_INIT_DONE,
+    GspLockdownNotice = bindings::NV_VGPU_MSG_EVENT_GSP_LOCKDOWN_NOTICE,
+    GspPostNoCat = bindings::NV_VGPU_MSG_EVENT_GSP_POST_NOCAT_RECORD,
     GspRunCpuSequencer = bindings::NV_VGPU_MSG_EVENT_GSP_RUN_CPU_SEQUENCER,
-    PostEvent = bindings::NV_VGPU_MSG_EVENT_POST_EVENT,
-    RcTriggered = bindings::NV_VGPU_MSG_EVENT_RC_TRIGGERED,
     MmuFaultQueued = bindings::NV_VGPU_MSG_EVENT_MMU_FAULT_QUEUED,
     OsErrorLog = bindings::NV_VGPU_MSG_EVENT_OS_ERROR_LOG,
-    GspPostNoCat = bindings::NV_VGPU_MSG_EVENT_GSP_POST_NOCAT_RECORD,
-    GspLockdownNotice = bindings::NV_VGPU_MSG_EVENT_GSP_LOCKDOWN_NOTICE,
+    PostEvent = bindings::NV_VGPU_MSG_EVENT_POST_EVENT,
+    RcTriggered = bindings::NV_VGPU_MSG_EVENT_RC_TRIGGERED,
     UcodeLibOsPrint = bindings::NV_VGPU_MSG_EVENT_UCODE_LIBOS_PRINT,
 }
 
@@ -227,34 +227,34 @@ impl fmt::Display for MsgFunction {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         match self {
             // Common function codes
-            MsgFunction::Nop => write!(f, "NOP"),
-            MsgFunction::SetGuestSystemInfo => write!(f, "SET_GUEST_SYSTEM_INFO"),
-            MsgFunction::AllocRoot => write!(f, "ALLOC_ROOT"),
+            MsgFunction::AllocChannelDma => write!(f, "ALLOC_CHANNEL_DMA"),
+            MsgFunction::AllocCtxDma => write!(f, "ALLOC_CTX_DMA"),
             MsgFunction::AllocDevice => write!(f, "ALLOC_DEVICE"),
             MsgFunction::AllocMemory => write!(f, "ALLOC_MEMORY"),
-            MsgFunction::AllocCtxDma => write!(f, "ALLOC_CTX_DMA"),
-            MsgFunction::AllocChannelDma => write!(f, "ALLOC_CHANNEL_DMA"),
-            MsgFunction::MapMemory => write!(f, "MAP_MEMORY"),
-            MsgFunction::BindCtxDma => write!(f, "BIND_CTX_DMA"),
             MsgFunction::AllocObject => write!(f, "ALLOC_OBJECT"),
+            MsgFunction::AllocRoot => write!(f, "ALLOC_ROOT"),
+            MsgFunction::BindCtxDma => write!(f, "BIND_CTX_DMA"),
             MsgFunction::Free => write!(f, "FREE"),
-            MsgFunction::Log => write!(f, "LOG"),
             MsgFunction::GetGspStaticInfo => write!(f, "GET_GSP_STATIC_INFO"),
-            MsgFunction::SetRegistry => write!(f, "SET_REGISTRY"),
-            MsgFunction::GspSetSystemInfo => write!(f, "GSP_SET_SYSTEM_INFO"),
+            MsgFunction::GetStaticInfo => write!(f, "GET_STATIC_INFO"),
             MsgFunction::GspInitPostObjGpu => write!(f, "GSP_INIT_POST_OBJGPU"),
             MsgFunction::GspRmControl => write!(f, "GSP_RM_CONTROL"),
-            MsgFunction::GetStaticInfo => write!(f, "GET_STATIC_INFO"),
+            MsgFunction::GspSetSystemInfo => write!(f, "GSP_SET_SYSTEM_INFO"),
+            MsgFunction::Log => write!(f, "LOG"),
+            MsgFunction::MapMemory => write!(f, "MAP_MEMORY"),
+            MsgFunction::Nop => write!(f, "NOP"),
+            MsgFunction::SetGuestSystemInfo => write!(f, "SET_GUEST_SYSTEM_INFO"),
+            MsgFunction::SetRegistry => write!(f, "SET_REGISTRY"),
 
             // Event codes
             MsgFunction::GspInitDone => write!(f, "INIT_DONE"),
+            MsgFunction::GspLockdownNotice => write!(f, "LOCKDOWN_NOTICE"),
+            MsgFunction::GspPostNoCat => write!(f, "NOCAT"),
             MsgFunction::GspRunCpuSequencer => write!(f, "RUN_CPU_SEQUENCER"),
-            MsgFunction::PostEvent => write!(f, "POST_EVENT"),
-            MsgFunction::RcTriggered => write!(f, "RC_TRIGGERED"),
             MsgFunction::MmuFaultQueued => write!(f, "MMU_FAULT_QUEUED"),
             MsgFunction::OsErrorLog => write!(f, "OS_ERROR_LOG"),
-            MsgFunction::GspPostNoCat => write!(f, "NOCAT"),
-            MsgFunction::GspLockdownNotice => write!(f, "LOCKDOWN_NOTICE"),
+            MsgFunction::PostEvent => write!(f, "POST_EVENT"),
+            MsgFunction::RcTriggered => write!(f, "RC_TRIGGERED"),
             MsgFunction::UcodeLibOsPrint => write!(f, "LIBOS_PRINT"),
         }
     }
@@ -265,38 +265,41 @@ impl TryFrom<u32> for MsgFunction {
 
     fn try_from(value: u32) -> Result<MsgFunction> {
         match value {
-            bindings::NV_VGPU_MSG_FUNCTION_NOP => Ok(MsgFunction::Nop),
-            bindings::NV_VGPU_MSG_FUNCTION_SET_GUEST_SYSTEM_INFO => {
-                Ok(MsgFunction::SetGuestSystemInfo)
-            }
-            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT => Ok(MsgFunction::AllocRoot),
+            // Common function codes
+            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CHANNEL_DMA => Ok(MsgFunction::AllocChannelDma),
+            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CTX_DMA => Ok(MsgFunction::AllocCtxDma),
             bindings::NV_VGPU_MSG_FUNCTION_ALLOC_DEVICE => Ok(MsgFunction::AllocDevice),
             bindings::NV_VGPU_MSG_FUNCTION_ALLOC_MEMORY => Ok(MsgFunction::AllocMemory),
-            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CTX_DMA => Ok(MsgFunction::AllocCtxDma),
-            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_CHANNEL_DMA => Ok(MsgFunction::AllocChannelDma),
-            bindings::NV_VGPU_MSG_FUNCTION_MAP_MEMORY => Ok(MsgFunction::MapMemory),
-            bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA => Ok(MsgFunction::BindCtxDma),
             bindings::NV_VGPU_MSG_FUNCTION_ALLOC_OBJECT => Ok(MsgFunction::AllocObject),
+            bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT => Ok(MsgFunction::AllocRoot),
+            bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA => Ok(MsgFunction::BindCtxDma),
             bindings::NV_VGPU_MSG_FUNCTION_FREE => Ok(MsgFunction::Free),
-            bindings::NV_VGPU_MSG_FUNCTION_LOG => Ok(MsgFunction::Log),
             bindings::NV_VGPU_MSG_FUNCTION_GET_GSP_STATIC_INFO => Ok(MsgFunction::GetGspStaticInfo),
-            bindings::NV_VGPU_MSG_FUNCTION_SET_REGISTRY => Ok(MsgFunction::SetRegistry),
-            bindings::NV_VGPU_MSG_FUNCTION_GSP_SET_SYSTEM_INFO => Ok(MsgFunction::GspSetSystemInfo),
+            bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO => Ok(MsgFunction::GetStaticInfo),
             bindings::NV_VGPU_MSG_FUNCTION_GSP_INIT_POST_OBJGPU => {
                 Ok(MsgFunction::GspInitPostObjGpu)
             }
             bindings::NV_VGPU_MSG_FUNCTION_GSP_RM_CONTROL => Ok(MsgFunction::GspRmControl),
-            bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO => Ok(MsgFunction::GetStaticInfo),
+            bindings::NV_VGPU_MSG_FUNCTION_GSP_SET_SYSTEM_INFO => Ok(MsgFunction::GspSetSystemInfo),
+            bindings::NV_VGPU_MSG_FUNCTION_LOG => Ok(MsgFunction::Log),
+            bindings::NV_VGPU_MSG_FUNCTION_MAP_MEMORY => Ok(MsgFunction::MapMemory),
+            bindings::NV_VGPU_MSG_FUNCTION_NOP => Ok(MsgFunction::Nop),
+            bindings::NV_VGPU_MSG_FUNCTION_SET_GUEST_SYSTEM_INFO => {
+                Ok(MsgFunction::SetGuestSystemInfo)
+            }
+            bindings::NV_VGPU_MSG_FUNCTION_SET_REGISTRY => Ok(MsgFunction::SetRegistry),
+
+            // Event codes
             bindings::NV_VGPU_MSG_EVENT_GSP_INIT_DONE => Ok(MsgFunction::GspInitDone),
+            bindings::NV_VGPU_MSG_EVENT_GSP_LOCKDOWN_NOTICE => Ok(MsgFunction::GspLockdownNotice),
+            bindings::NV_VGPU_MSG_EVENT_GSP_POST_NOCAT_RECORD => Ok(MsgFunction::GspPostNoCat),
             bindings::NV_VGPU_MSG_EVENT_GSP_RUN_CPU_SEQUENCER => {
                 Ok(MsgFunction::GspRunCpuSequencer)
             }
-            bindings::NV_VGPU_MSG_EVENT_POST_EVENT => Ok(MsgFunction::PostEvent),
-            bindings::NV_VGPU_MSG_EVENT_RC_TRIGGERED => Ok(MsgFunction::RcTriggered),
             bindings::NV_VGPU_MSG_EVENT_MMU_FAULT_QUEUED => Ok(MsgFunction::MmuFaultQueued),
             bindings::NV_VGPU_MSG_EVENT_OS_ERROR_LOG => Ok(MsgFunction::OsErrorLog),
-            bindings::NV_VGPU_MSG_EVENT_GSP_POST_NOCAT_RECORD => Ok(MsgFunction::GspPostNoCat),
-            bindings::NV_VGPU_MSG_EVENT_GSP_LOCKDOWN_NOTICE => Ok(MsgFunction::GspLockdownNotice),
+            bindings::NV_VGPU_MSG_EVENT_POST_EVENT => Ok(MsgFunction::PostEvent),
+            bindings::NV_VGPU_MSG_EVENT_RC_TRIGGERED => Ok(MsgFunction::RcTriggered),
             bindings::NV_VGPU_MSG_EVENT_UCODE_LIBOS_PRINT => Ok(MsgFunction::UcodeLibOsPrint),
             _ => Err(EINVAL),
         }

-- 
2.53.0

[PATCH v2 2/9] gpu: nova-core: gsp: add mechanism to wait for space on command queue

[Eliot Courtney]

Add a timeout to `allocate_command` which waits for space on the GSP
command queue. It uses a similar timeout to nouveau.

This lets `send_command` wait for space to free up in the command queue.
This is required to support continuation records which can fill up the
queue.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 39 +++++++++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 46819a82a51a..f7f3cf2c7443 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -243,6 +243,19 @@ fn new(dev: &device::Device<device::Bound>) -> Result<Self> {
         }
     }
 
+    /// Returns the size of the region of the CPU message queue that the driver is currently allowed
+    /// to write to, in bytes.
+    fn driver_write_area_size(&self) -> usize {
+        let tx = self.cpu_write_ptr();
+        let rx = self.gsp_read_ptr();
+
+        // `rx` and `tx` are both in `0..MSGQ_NUM_PAGES` per the invariants of `gsp_read_ptr` and
+        // `cpu_write_ptr`. The minimum value case is where `rx == 0` and `tx == MSGQ_NUM_PAGES -
+        // 1`, which gives `0 + MSGQ_NUM_PAGES - (MSGQ_NUM_PAGES - 1) - 1 == 0`.
+        let slots = (rx + MSGQ_NUM_PAGES - tx - 1) % MSGQ_NUM_PAGES;
+        num::u32_as_usize(slots) * GSP_PAGE_SIZE
+    }
+
     /// Returns the region of the GSP message queue that the driver is currently allowed to read
     /// from.
     ///
@@ -268,15 +281,22 @@ fn new(dev: &device::Device<device::Bound>) -> Result<Self> {
     }
 
     /// Allocates a region on the command queue that is large enough to send a command of `size`
-    /// bytes.
+    /// bytes, waiting for space to become available based on the provided timeout.
     ///
     /// This returns a [`GspCommand`] ready to be written to by the caller.
     ///
     /// # Errors
     ///
-    /// - `EAGAIN` if the driver area is too small to hold the requested command.
+    /// - `ETIMEDOUT` if space does not become available within the timeout.
     /// - `EIO` if the command header is not properly aligned.
-    fn allocate_command(&mut self, size: usize) -> Result<GspCommand<'_>> {
+    fn allocate_command(&mut self, size: usize, timeout: Delta) -> Result<GspCommand<'_>> {
+        read_poll_timeout(
+            || Ok(self.driver_write_area_size()),
+            |available_bytes| *available_bytes >= size_of::<GspMsgElement>() + size,
+            Delta::ZERO,
+            timeout,
+        )?;
+
         // Get the current writable area as an array of bytes.
         let (slice_1, slice_2) = {
             let (slice_1, slice_2) = self.driver_write_area();
@@ -285,13 +305,6 @@ fn allocate_command(&mut self, size: usize) -> Result<GspCommand<'_>> {
             (slice_1.as_flattened_mut(), slice_2.as_flattened_mut())
         };
 
-        // If the GSP is still processing previous messages the shared region
-        // may be full in which case we will have to retry once the GSP has
-        // processed the existing commands.
-        if size_of::<GspMsgElement>() + size > slice_1.len() + slice_2.len() {
-            return Err(EAGAIN);
-        }
-
         // Extract area for the `GspMsgElement`.
         let (header, slice_1) = GspMsgElement::from_bytes_mut_prefix(slice_1).ok_or(EIO)?;
 
@@ -484,7 +497,7 @@ fn notify_gsp(bar: &Bar0) {
     ///
     /// # Errors
     ///
-    /// - `EAGAIN` if there was not enough space in the command queue to send the command.
+    /// - `ETIMEDOUT` if space does not become available within the timeout.
     /// - `EIO` if the variable payload requested by the command has not been entirely
     ///   written to by its [`CommandToGsp::init_variable_payload`] method.
     ///
@@ -496,7 +509,9 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
         Error: From<M::InitError>,
     {
         let command_size = size_of::<M::Command>() + command.variable_payload_len();
-        let dst = self.gsp_mem.allocate_command(command_size)?;
+        let dst = self
+            .gsp_mem
+            .allocate_command(command_size, Delta::from_secs(1))?;
 
         // Extract area for the command itself.
         let (cmd, payload_1) = M::Command::from_bytes_mut_prefix(dst.contents.0).ok_or(EIO)?;

-- 
2.53.0

[PATCH v2 3/9] rust: add EMSGSIZE error code

[Eliot Courtney]

Add the EMSGSIZE error code, which indicates that a message is too
long.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 rust/kernel/error.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 258b12afdcba..10fcf1f0404d 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -67,6 +67,7 @@ macro_rules! declare_err {
     declare_err!(EDOM, "Math argument out of domain of func.");
     declare_err!(ERANGE, "Math result not representable.");
     declare_err!(EOVERFLOW, "Value too large for defined data type.");
+    declare_err!(EMSGSIZE, "Message too long.");
     declare_err!(ETIMEDOUT, "Connection timed out.");
     declare_err!(ERESTARTSYS, "Restart the system call.");
     declare_err!(ERESTARTNOINTR, "System call was interrupted by a signal and will be restarted.");

-- 
2.53.0

[PATCH v2 4/9] gpu: nova-core: gsp: add checking oversized commands

[Eliot Courtney]

The limit is 16 pages for a single command sent to the GSP. Return an
error if `allocate_command` is called with a too large size.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs                 | 7 ++++++-
 drivers/gpu/nova-core/gsp/fw.rs                   | 4 ++++
 drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs | 1 +
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index f7f3cf2c7443..ae4aa7562dee 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -33,7 +33,8 @@
             GspMsgElement,
             MsgFunction,
             MsgqRxHeader,
-            MsgqTxHeader, //
+            MsgqTxHeader,
+            GSP_MSG_QUEUE_ELEMENT_SIZE_MAX, //
         },
         PteArray,
         GSP_PAGE_SHIFT,
@@ -287,9 +288,13 @@ fn driver_write_area_size(&self) -> usize {
     ///
     /// # Errors
     ///
+    /// - `EMSGSIZE` if the command is larger than [`GSP_MSG_QUEUE_ELEMENT_SIZE_MAX`].
     /// - `ETIMEDOUT` if space does not become available within the timeout.
     /// - `EIO` if the command header is not properly aligned.
     fn allocate_command(&mut self, size: usize, timeout: Delta) -> Result<GspCommand<'_>> {
+        if size_of::<GspMsgElement>() + size > GSP_MSG_QUEUE_ELEMENT_SIZE_MAX {
+            return Err(EMSGSIZE);
+        }
         read_poll_timeout(
             || Ok(self.driver_write_area_size()),
             |available_bytes| *available_bytes >= size_of::<GspMsgElement>() + size,
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index 5b96f5e622a4..c604f423fff3 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -40,6 +40,10 @@
     },
 };
 
+/// Maximum size of a single GSP message queue element in bytes.
+pub(crate) const GSP_MSG_QUEUE_ELEMENT_SIZE_MAX: usize =
+    num::u32_as_usize(bindings::GSP_MSG_QUEUE_ELEMENT_SIZE_MAX);
+
 /// Empty type to group methods related to heap parameters for running the GSP firmware.
 enum GspFwHeapParams {}
 
diff --git a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
index 6d25fe0bffa9..334e8be5fde8 100644
--- a/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
+++ b/drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
@@ -43,6 +43,7 @@ fn fmt(&self, fmt: &mut ::core::fmt::Formatter<'_>) -> ::core::fmt::Result {
 pub const GSP_FW_WPR_META_REVISION: u32 = 1;
 pub const GSP_FW_WPR_META_MAGIC: i64 = -2577556379034558285;
 pub const REGISTRY_TABLE_ENTRY_TYPE_DWORD: u32 = 1;
+pub const GSP_MSG_QUEUE_ELEMENT_SIZE_MAX: u32 = 65536;
 pub type __u8 = ffi::c_uchar;
 pub type __u16 = ffi::c_ushort;
 pub type __u32 = ffi::c_uint;

-- 
2.53.0

[PATCH v2 5/9] gpu: nova-core: gsp: clarify invariant on command queue

[Eliot Courtney]

Clarify why using only the first returned slice from allocate_command
for the message headers is okay.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index ae4aa7562dee..08b8c04909a6 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -518,7 +518,9 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
             .gsp_mem
             .allocate_command(command_size, Delta::from_secs(1))?;
 
-        // Extract area for the command itself.
+        // Extract area for the command itself. The GSP message header and the command header
+        // together are guaranteed to fit entirely into a single page, so it's ok to only look
+        // at `dst.contents.0` here.
         let (cmd, payload_1) = M::Command::from_bytes_mut_prefix(dst.contents.0).ok_or(EIO)?;
 
         // Fill the header and command in-place.

-- 
2.53.0

[PATCH v2 6/9] gpu: nova-core: gsp: unconditionally call variable payload handling

[Eliot Courtney]

Unconditionally call the variable length payload code, which is a no-op
if there is no such payload but could defensively catch some coding
errors by e.g. checking that the allocated size is completely filled.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 16 +++++++---------
 1 file changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 08b8c04909a6..1547687834f8 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -532,16 +532,14 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
             command.init().__init(core::ptr::from_mut(cmd))?;
         }
 
-        // Fill the variable-length payload.
-        if command_size > size_of::<M::Command>() {
-            let mut sbuffer =
-                SBufferIter::new_writer([&mut payload_1[..], &mut dst.contents.1[..]]);
-            command.init_variable_payload(&mut sbuffer)?;
-
-            if !sbuffer.is_empty() {
-                return Err(EIO);
-            }
+        // Fill the variable-length payload, which may be empty.
+        let mut sbuffer = SBufferIter::new_writer([&mut payload_1[..], &mut dst.contents.1[..]]);
+        command.init_variable_payload(&mut sbuffer)?;
+
+        if !sbuffer.is_empty() {
+            return Err(EIO);
         }
+        drop(sbuffer);
 
         // Compute checksum now that the whole message is ready.
         dst.header

-- 
2.53.0

[PATCH v2 7/9] gpu: nova-core: gsp: add command_size helper

[Eliot Courtney]

Add a helper function which computes the size of a command.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index 1547687834f8..f832252ae45c 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -437,6 +437,15 @@ struct GspMessage<'a> {
     contents: (&'a [u8], &'a [u8]),
 }
 
+/// Computes the total size of the command (not including the [`GspMsgElement`] header), including
+/// its variable-length payload.
+fn command_size<M>(command: &M) -> usize
+where
+    M: CommandToGsp,
+{
+    size_of::<M::Command>() + command.variable_payload_len()
+}
+
 /// GSP command queue.
 ///
 /// Provides the ability to send commands and receive messages from the GSP using a shared memory
@@ -513,7 +522,7 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
         // This allows all error types, including `Infallible`, to be used for `M::InitError`.
         Error: From<M::InitError>,
     {
-        let command_size = size_of::<M::Command>() + command.variable_payload_len();
+        let command_size = command_size(&command);
         let dst = self
             .gsp_mem
             .allocate_command(command_size, Delta::from_secs(1))?;

-- 
2.53.0

[PATCH v2 8/9] gpu: nova-core: gsp: support large RPCs via continuation record

[Eliot Courtney]

Splits large RPCs if necessary and sends the remaining parts using
continuation records. RPCs that do not need continuation records
continue to write directly into the command buffer. Ones that do write
into a staging buffer first, so there is one copy.

Continuation record for receive is not necessary to support at the
moment because those replies do not need to be read and are currently
drained by retrying `receive_msg` on ERANGE.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/cmdq.rs     |  43 +++++++++-
 drivers/gpu/nova-core/gsp/commands.rs | 143 +++++++++++++++++++++++++++++++++-
 drivers/gpu/nova-core/gsp/fw.rs       |   5 ++
 3 files changed, 187 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
index f832252ae45c..402b0b9418ab 100644
--- a/drivers/gpu/nova-core/gsp/cmdq.rs
+++ b/drivers/gpu/nova-core/gsp/cmdq.rs
@@ -29,6 +29,10 @@
 use crate::{
     driver::Bar0,
     gsp::{
+        commands::{
+            ContinuationRecord,
+            SplitState, //
+        },
         fw::{
             GspMsgElement,
             MsgFunction,
@@ -439,7 +443,7 @@ struct GspMessage<'a> {
 
 /// Computes the total size of the command (not including the [`GspMsgElement`] header), including
 /// its variable-length payload.
-fn command_size<M>(command: &M) -> usize
+pub(crate) fn command_size<M>(command: &M) -> usize
 where
     M: CommandToGsp,
 {
@@ -507,7 +511,7 @@ fn notify_gsp(bar: &Bar0) {
             .write(bar);
     }
 
-    /// Sends `command` to the GSP.
+    /// Sends `command` to the GSP, without splitting it.
     ///
     /// # Errors
     ///
@@ -516,7 +520,7 @@ fn notify_gsp(bar: &Bar0) {
     ///   written to by its [`CommandToGsp::init_variable_payload`] method.
     ///
     /// Error codes returned by the command initializers are propagated as-is.
-    pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
+    fn send_single_command<M>(&mut self, bar: &Bar0, command: M) -> Result
     where
         M: CommandToGsp,
         // This allows all error types, including `Infallible`, to be used for `M::InitError`.
@@ -575,6 +579,39 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
         Ok(())
     }
 
+    /// Sends `command` to the GSP.
+    ///
+    /// The command may be split into multiple messages if it is large.
+    ///
+    /// # Errors
+    ///
+    /// - `ETIMEDOUT` if space does not become available within the timeout.
+    /// - `EIO` if the variable payload requested by the command has not been entirely
+    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
+    ///
+    /// Error codes returned by the command initializers are propagated as-is.
+    pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
+    where
+        M: CommandToGsp,
+        Error: From<M::InitError>,
+    {
+        let mut state = SplitState::new(&command)?;
+
+        self.send_single_command(bar, state.command(command))?;
+
+        while let Some(continuation) = state.next_continuation_record() {
+            dev_dbg!(
+                &self.dev,
+                "GSP RPC: send continuation: size=0x{:x}\n",
+                command_size(&continuation),
+            );
+            // Turbofish needed because the compiler cannot infer M here.
+            self.send_single_command::<ContinuationRecord<'_>>(bar, continuation)?;
+        }
+
+        Ok(())
+    }
+
     /// Wait for a message to become available on the message queue.
     ///
     /// This works purely at the transport layer and does not interpret or validate the message
diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
index 8f270eca33be..e722c6091ec8 100644
--- a/drivers/gpu/nova-core/gsp/commands.rs
+++ b/drivers/gpu/nova-core/gsp/commands.rs
@@ -4,6 +4,7 @@
     array,
     convert::Infallible,
     ffi::FromBytesUntilNulError,
+    marker::PhantomData,
     str::Utf8Error, //
 };
 
@@ -22,13 +23,16 @@
     driver::Bar0,
     gsp::{
         cmdq::{
+            command_size,
             Cmdq,
             CommandToGsp,
             MessageFromGsp, //
         },
         fw::{
             commands::*,
-            MsgFunction, //
+            GspMsgElement,
+            MsgFunction,
+            GSP_MSG_QUEUE_ELEMENT_SIZE_MAX, //
         },
     },
     sbuffer::SBufferIter,
@@ -242,3 +246,140 @@ pub(crate) fn get_gsp_info(cmdq: &mut Cmdq, bar: &Bar0) -> Result<GetGspStaticIn
         }
     }
 }
+
+/// The `ContinuationRecord` command.
+pub(crate) struct ContinuationRecord<'a> {
+    data: &'a [u8],
+}
+
+impl<'a> ContinuationRecord<'a> {
+    /// Creates a new `ContinuationRecord` command with the given data.
+    pub(crate) fn new(data: &'a [u8]) -> Self {
+        Self { data }
+    }
+}
+
+impl<'a> CommandToGsp for ContinuationRecord<'a> {
+    const FUNCTION: MsgFunction = MsgFunction::ContinuationRecord;
+    type Command = ();
+    type InitError = Infallible;
+
+    fn init(&self) -> impl Init<Self::Command, Self::InitError> {
+        <()>::init_zeroed()
+    }
+
+    fn variable_payload_len(&self) -> usize {
+        self.data.len()
+    }
+
+    fn init_variable_payload(
+        &self,
+        dst: &mut SBufferIter<core::array::IntoIter<&mut [u8], 2>>,
+    ) -> Result {
+        dst.write_all(self.data)
+    }
+}
+
+/// Wrapper that splits a command across continuation records if needed.
+pub(crate) struct SplitState<C: CommandToGsp> {
+    state: Option<(KVVec<u8>, usize)>,
+    _phantom: PhantomData<C>,
+}
+
+impl<C: CommandToGsp> SplitState<C> {
+    /// Maximum command size that fits in a single queue element.
+    const MAX_CMD_SIZE: usize = GSP_MSG_QUEUE_ELEMENT_SIZE_MAX - size_of::<GspMsgElement>();
+
+    /// Maximum size of the variable payload that can be sent in the main command.
+    const MAX_FIRST_PAYLOAD_SIZE: usize = Self::MAX_CMD_SIZE - size_of::<C::Command>();
+
+    /// Creates a new `SplitState` for the given command.
+    ///
+    /// If the command is too large, it will be split into a main command and some number of
+    /// continuation records.
+    pub(crate) fn new(inner: &C) -> Result<Self> {
+        if command_size(inner) > Self::MAX_CMD_SIZE {
+            let mut staging =
+                KVVec::<u8>::from_elem(0u8, inner.variable_payload_len(), GFP_KERNEL)?;
+            let mut sbuffer = SBufferIter::new_writer([staging.as_mut_slice(), &mut []]);
+            inner.init_variable_payload(&mut sbuffer)?;
+            if !sbuffer.is_empty() {
+                return Err(EIO);
+            }
+            drop(sbuffer);
+
+            Ok(Self {
+                state: Some((staging, Self::MAX_FIRST_PAYLOAD_SIZE)),
+                _phantom: PhantomData,
+            })
+        } else {
+            Ok(Self {
+                state: None,
+                _phantom: PhantomData,
+            })
+        }
+    }
+
+    /// Returns the main command.
+    pub(crate) fn command(&self, inner: C) -> SplitCommand<'_, C> {
+        if let Some((staging, _)) = &self.state {
+            SplitCommand::Split(inner, staging)
+        } else {
+            SplitCommand::Single(inner)
+        }
+    }
+
+    /// Returns the next continuation record, or `None` if there are no more.
+    pub(crate) fn next_continuation_record(&mut self) -> Option<ContinuationRecord<'_>> {
+        let (staging, offset) = self.state.as_mut()?;
+
+        let remaining = staging.len() - *offset;
+        if remaining > 0 {
+            let chunk_size = remaining.min(Self::MAX_CMD_SIZE);
+            let record = ContinuationRecord::new(&staging[*offset..(*offset + chunk_size)]);
+            *offset += chunk_size;
+            Some(record)
+        } else {
+            None
+        }
+    }
+}
+
+/// Wrapper enum that represents either a single command or a split command with its staging buffer.
+pub(crate) enum SplitCommand<'a, C: CommandToGsp> {
+    Single(C),
+    Split(C, &'a [u8]),
+}
+
+impl<'a, C: CommandToGsp> CommandToGsp for SplitCommand<'a, C> {
+    const FUNCTION: MsgFunction = C::FUNCTION;
+    type Command = C::Command;
+    type InitError = C::InitError;
+
+    fn init(&self) -> impl Init<Self::Command, Self::InitError> {
+        match self {
+            SplitCommand::Single(cmd) => cmd.init(),
+            SplitCommand::Split(cmd, _) => cmd.init(),
+        }
+    }
+
+    fn variable_payload_len(&self) -> usize {
+        match self {
+            SplitCommand::Single(cmd) => cmd.variable_payload_len(),
+            SplitCommand::Split(_, _) => SplitState::<C>::MAX_FIRST_PAYLOAD_SIZE,
+        }
+    }
+
+    fn init_variable_payload(
+        &self,
+        dst: &mut SBufferIter<core::array::IntoIter<&mut [u8], 2>>,
+    ) -> Result {
+        match self {
+            SplitCommand::Single(cmd) => cmd.init_variable_payload(dst),
+            SplitCommand::Split(_, staging) => {
+                dst.write_all(&staging[..self.variable_payload_len()])
+            }
+        }
+    }
+}
+
diff --git a/drivers/gpu/nova-core/gsp/fw.rs b/drivers/gpu/nova-core/gsp/fw.rs
index c604f423fff3..1a317dfb0bc9 100644
--- a/drivers/gpu/nova-core/gsp/fw.rs
+++ b/drivers/gpu/nova-core/gsp/fw.rs
@@ -203,6 +203,7 @@ pub(crate) enum MsgFunction {
     AllocObject = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_OBJECT,
     AllocRoot = bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT,
     BindCtxDma = bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA,
+    ContinuationRecord = bindings::NV_VGPU_MSG_FUNCTION_CONTINUATION_RECORD,
     Free = bindings::NV_VGPU_MSG_FUNCTION_FREE,
     GetGspStaticInfo = bindings::NV_VGPU_MSG_FUNCTION_GET_GSP_STATIC_INFO,
     GetStaticInfo = bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO,
@@ -238,6 +239,7 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
             MsgFunction::AllocObject => write!(f, "ALLOC_OBJECT"),
             MsgFunction::AllocRoot => write!(f, "ALLOC_ROOT"),
             MsgFunction::BindCtxDma => write!(f, "BIND_CTX_DMA"),
+            MsgFunction::ContinuationRecord => write!(f, "CONTINUATION_RECORD"),
             MsgFunction::Free => write!(f, "FREE"),
             MsgFunction::GetGspStaticInfo => write!(f, "GET_GSP_STATIC_INFO"),
             MsgFunction::GetStaticInfo => write!(f, "GET_STATIC_INFO"),
@@ -277,6 +279,9 @@ fn try_from(value: u32) -> Result<MsgFunction> {
             bindings::NV_VGPU_MSG_FUNCTION_ALLOC_OBJECT => Ok(MsgFunction::AllocObject),
             bindings::NV_VGPU_MSG_FUNCTION_ALLOC_ROOT => Ok(MsgFunction::AllocRoot),
             bindings::NV_VGPU_MSG_FUNCTION_BIND_CTX_DMA => Ok(MsgFunction::BindCtxDma),
+            bindings::NV_VGPU_MSG_FUNCTION_CONTINUATION_RECORD => {
+                Ok(MsgFunction::ContinuationRecord)
+            }
             bindings::NV_VGPU_MSG_FUNCTION_FREE => Ok(MsgFunction::Free),
             bindings::NV_VGPU_MSG_FUNCTION_GET_GSP_STATIC_INFO => Ok(MsgFunction::GetGspStaticInfo),
             bindings::NV_VGPU_MSG_FUNCTION_GET_STATIC_INFO => Ok(MsgFunction::GetStaticInfo),

-- 
2.53.0

[PATCH v2 9/9] gpu: nova-core: gsp: add tests for SplitState

[Eliot Courtney]

Add tests for SplitState. They cover boundary conditions at the split
points to make sure the right number of continuation records are made.
They also check that the data concatenated is correct.

Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
---
 drivers/gpu/nova-core/gsp/commands.rs | 113 ++++++++++++++++++++++++++++++++++
 1 file changed, 113 insertions(+)

diff --git a/drivers/gpu/nova-core/gsp/commands.rs b/drivers/gpu/nova-core/gsp/commands.rs
index e722c6091ec8..1683ebb4c685 100644
--- a/drivers/gpu/nova-core/gsp/commands.rs
+++ b/drivers/gpu/nova-core/gsp/commands.rs
@@ -383,3 +383,116 @@ fn init_variable_payload(
     }
 }
 
+#[kunit_tests(nova_core_gsp_commands)]
+mod tests {
+    use super::*;
+
+    struct TestPayload {
+        data: KVVec<u8>,
+    }
+
+    impl TestPayload {
+        fn generate_pattern(len: usize) -> Result<KVVec<u8>> {
+            let mut data = KVVec::with_capacity(len, GFP_KERNEL)?;
+            for i in 0..len {
+                data.push(i as u8, GFP_KERNEL)?;
+            }
+            Ok(data)
+        }
+
+        fn new(len: usize) -> Result<Self> {
+            Ok(Self {
+                data: Self::generate_pattern(len)?,
+            })
+        }
+    }
+
+    impl CommandToGsp for TestPayload {
+        const FUNCTION: MsgFunction = MsgFunction::Nop;
+        type Command = ();
+        type InitError = Infallible;
+
+        fn init(&self) -> impl Init<Self::Command, Self::InitError> {
+            <()>::init_zeroed()
+        }
+
+        fn variable_payload_len(&self) -> usize {
+            self.data.len()
+        }
+
+        fn init_variable_payload(
+            &self,
+            dst: &mut SBufferIter<core::array::IntoIter<&mut [u8], 2>>,
+        ) -> Result {
+            dst.write_all(self.data.as_slice())
+        }
+    }
+
+    const MAX_CMD_SIZE: usize = SplitState::<TestPayload>::MAX_CMD_SIZE;
+
+    fn read_payload(cmd: &impl CommandToGsp) -> Result<KVVec<u8>> {
+        let len = cmd.variable_payload_len();
+        let mut buf = KVVec::from_elem(0u8, len, GFP_KERNEL)?;
+        let mut sbuf = SBufferIter::new_writer([buf.as_mut_slice(), &mut []]);
+        cmd.init_variable_payload(&mut sbuf)?;
+        drop(sbuf);
+        Ok(buf)
+    }
+
+    struct SplitTest {
+        payload_size: usize,
+        num_continuations: usize,
+    }
+
+    fn check_split(t: SplitTest) -> Result {
+        let payload = TestPayload::new(t.payload_size)?;
+        let mut state = SplitState::new(&payload)?;
+
+        let mut buf = read_payload(&state.command(payload))?;
+        assert!(buf.len() <= MAX_CMD_SIZE);
+
+        let mut num_continuations = 0;
+        while let Some(cont) = state.next_continuation_record() {
+            let payload = read_payload(&cont)?;
+            assert!(payload.len() <= MAX_CMD_SIZE);
+            buf.extend_from_slice(&payload, GFP_KERNEL)?;
+            num_continuations += 1;
+        }
+
+        assert_eq!(num_continuations, t.num_continuations);
+        assert_eq!(
+            buf.as_slice(),
+            TestPayload::generate_pattern(t.payload_size)?.as_slice()
+        );
+        Ok(())
+    }
+
+    #[test]
+    fn split_command() -> Result {
+        check_split(SplitTest {
+            payload_size: 0,
+            num_continuations: 0,
+        })?;
+        check_split(SplitTest {
+            payload_size: MAX_CMD_SIZE,
+            num_continuations: 0,
+        })?;
+        check_split(SplitTest {
+            payload_size: MAX_CMD_SIZE + 1,
+            num_continuations: 1,
+        })?;
+        check_split(SplitTest {
+            payload_size: MAX_CMD_SIZE * 2,
+            num_continuations: 1,
+        })?;
+        check_split(SplitTest {
+            payload_size: MAX_CMD_SIZE * 2 + 1,
+            num_continuations: 2,
+        })?;
+        check_split(SplitTest {
+            payload_size: MAX_CMD_SIZE * 3 + MAX_CMD_SIZE / 2,
+            num_continuations: 3,
+        })?;
+        Ok(())
+    }
+}

-- 
2.53.0

Re: [PATCH v2 0/9] gpu: nova-core: gsp: add continuation record support

[Zhi Wang]

On Thu, 19 Feb 2026 16:30:49 +0900
Eliot Courtney <ecourtney@nvidia.com> wrote:

Tested-by: Zhi Wang <zhiw@nvidia.com>

> GSP commands over 16 pages need to be sent using "continuation
> records" which essentially means splitting the payload over multiple
> commands.
> 
> This series adds a command type `ContinuationRecord` which just writes
> its header and whatever payload it is given. It also adds types
> `SplitState` and `SplitCommand` which support splitting a large RPC
> into smaller ones while transparently letting regular sized RPCs be
> sent without extra copies.
> 
> The send pathway uses `SplitState` to send all commands, but if
> the command fits into 16 pages, it still writes directly into the
> command queue. If it is larger than 16 pages and needs continuation
> records, it writes into a staging buffer, so there is one copy.
> 
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
> Changes in v2:
> - Added doccoments
> - Renamed driver_bytes_available_to_write to driver_write_area_size
> - allocate_command_with_timeout merged allocate_command with timeout
> parameter
> - Replaced hardcoded GSP_PAGE_SIZE * 16 with bindings
> - Changed oversized command error from EIO to EMSGSIZE
> - Added EMSGSIZE to kernel/error.rs
> - Split WrappingCommand functionality into SplitState + SplitCommand
> enum
> - Made max_size a const (MAX_CMD_SIZE)
> - Removed send_continuation_record + added comment for type inference
> - send_single_command now consumes the command
> - Extracted command_size + used in SplitState 
> - Link to v1:
> https://lore.kernel.org/r/20260212-cmdq-continuation-v1-0-73079ded55e6@nvidia.com
> 
> ---
> Eliot Courtney (9):
>       gpu: nova-core: gsp: sort MsgFunction variants alphabetically
>       gpu: nova-core: gsp: add mechanism to wait for space on command
> queue rust: add EMSGSIZE error code
>       gpu: nova-core: gsp: add checking oversized commands
>       gpu: nova-core: gsp: clarify invariant on command queue
>       gpu: nova-core: gsp: unconditionally call variable payload
> handling gpu: nova-core: gsp: add command_size helper
>       gpu: nova-core: gsp: support large RPCs via continuation record
>       gpu: nova-core: gsp: add tests for SplitState
> 
>  drivers/gpu/nova-core/gsp/cmdq.rs                 | 118 +++++++---
>  drivers/gpu/nova-core/gsp/commands.rs             | 256
> +++++++++++++++++++++- drivers/gpu/nova-core/gsp/fw.rs
>    | 106 +++++---- drivers/gpu/nova-core/gsp/fw/r570_144/bindings.rs
> |   1 + rust/kernel/error.rs                              |   1 +
>  5 files changed, 408 insertions(+), 74 deletions(-)
> ---
> base-commit: 956b9cbd7f156c8672dac94a00de3c6a0939c692
> change-id: 20260203-cmdq-continuation-b99f3d5966c3
> 
> Best regards,

Re: [PATCH v2 0/9] gpu: nova-core: gsp: add continuation record support

[Alexandre Courbot]

Hi Eliot,

On Thu Feb 19, 2026 at 4:30 PM JST, Eliot Courtney wrote:
> GSP commands over 16 pages need to be sent using "continuation records"
> which essentially means splitting the payload over multiple commands.
>
> This series adds a command type `ContinuationRecord` which just writes
> its header and whatever payload it is given. It also adds types
> `SplitState` and `SplitCommand` which support splitting a large RPC
> into smaller ones while transparently letting regular sized RPCs be sent
> without extra copies.
>
> The send pathway uses `SplitState` to send all commands, but if
> the command fits into 16 pages, it still writes directly into the
> command queue. If it is larger than 16 pages and needs continuation
> records, it writes into a staging buffer, so there is one copy.
>
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>

Thanks, this looks solid - unfortunately it fails to apply on top of
`drm-rust-next` (not your fault, the patchset was sent before -rc1 got
tagged). Patch 1 has a trivial conflict due to the removal of the
`Display` implementation, but patch 8 does not even give me the option
to resolve anything. Could you rebase on top of `drm-rust-next` and send
a v3? I would like to experiment a bit with patch 8 but cannot do it
unfortunately.

Re: [PATCH v2 7/9] gpu: nova-core: gsp: add command_size helper

[Alexandre Courbot]

On Thu Feb 19, 2026 at 4:30 PM JST, Eliot Courtney wrote:
> Add a helper function which computes the size of a command.
>
> Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
> ---
>  drivers/gpu/nova-core/gsp/cmdq.rs | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/nova-core/gsp/cmdq.rs b/drivers/gpu/nova-core/gsp/cmdq.rs
> index 1547687834f8..f832252ae45c 100644
> --- a/drivers/gpu/nova-core/gsp/cmdq.rs
> +++ b/drivers/gpu/nova-core/gsp/cmdq.rs
> @@ -437,6 +437,15 @@ struct GspMessage<'a> {
>      contents: (&'a [u8], &'a [u8]),
>  }
>  
> +/// Computes the total size of the command (not including the [`GspMsgElement`] header), including
> +/// its variable-length payload.

This comment reads a bit funny with the "not including but including".
How about "... size of the command (including its variable-length
payload) without the [`GspMsgElement`] header" ?

Re: [PATCH v2 8/9] gpu: nova-core: gsp: support large RPCs via continuation record

[Alexandre Courbot]

On Thu Feb 19, 2026 at 4:30 PM JST, Eliot Courtney wrote:
<snip>
> @@ -575,6 +579,39 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
>          Ok(())
>      }
>  
> +    /// Sends `command` to the GSP.
> +    ///
> +    /// The command may be split into multiple messages if it is large.
> +    ///
> +    /// # Errors
> +    ///
> +    /// - `ETIMEDOUT` if space does not become available within the timeout.
> +    /// - `EIO` if the variable payload requested by the command has not been entirely
> +    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
> +    ///
> +    /// Error codes returned by the command initializers are propagated as-is.
> +    pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
> +    where
> +        M: CommandToGsp,
> +        Error: From<M::InitError>,
> +    {
> +        let mut state = SplitState::new(&command)?;
> +
> +        self.send_single_command(bar, state.command(command))?;

I think it would be nice to send the actual command (and not the
`SplitCommand`) when commands don't need to be split. Split commands are
supposed to be the exception, but the current code makes us use them
unconditionally.

So something like:

    if command_size(&command) <= MAX_CMD_SIZE {
          self.send_single_command(bar, command)
      } else {
      // Split and send the parts
      ...
      }

would read better IMHO. You can have a
`SplitCommand::command_needs_splitting` method if you want to avoid
comparing against the const in `send_command`, but honestly I think this
is self-documenting already - you split the command because it is larger
than the maximum supported size of the queue.

It also would have the benefit of simplifying `SplitState` and
`SplitCommand` since they wouldn't have to handle the non-split case at
all. Actually you could just have a method that consumes the command and
returns a tuple with the `SplitCommand` wrapping it, and its
continuation records. That way I suspect you also remove the need to
pass `command` twice.

Re: [PATCH v2 8/9] gpu: nova-core: gsp: support large RPCs via continuation record

[Alexandre Courbot]

On Thu Feb 26, 2026 at 1:40 PM JST, Alexandre Courbot wrote:
> On Thu Feb 19, 2026 at 4:30 PM JST, Eliot Courtney wrote:
> <snip>
>> @@ -575,6 +579,39 @@ pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
>>          Ok(())
>>      }
>>  
>> +    /// Sends `command` to the GSP.
>> +    ///
>> +    /// The command may be split into multiple messages if it is large.
>> +    ///
>> +    /// # Errors
>> +    ///
>> +    /// - `ETIMEDOUT` if space does not become available within the timeout.
>> +    /// - `EIO` if the variable payload requested by the command has not been entirely
>> +    ///   written to by its [`CommandToGsp::init_variable_payload`] method.
>> +    ///
>> +    /// Error codes returned by the command initializers are propagated as-is.
>> +    pub(crate) fn send_command<M>(&mut self, bar: &Bar0, command: M) -> Result
>> +    where
>> +        M: CommandToGsp,
>> +        Error: From<M::InitError>,
>> +    {
>> +        let mut state = SplitState::new(&command)?;
>> +
>> +        self.send_single_command(bar, state.command(command))?;
>
> I think it would be nice to send the actual command (and not the
> `SplitCommand`) when commands don't need to be split. Split commands are
> supposed to be the exception, but the current code makes us use them
> unconditionally.
>
> So something like:
>
>     if command_size(&command) <= MAX_CMD_SIZE {
>           self.send_single_command(bar, command)
>       } else {
>       // Split and send the parts
>       ...
>       }
>
> would read better IMHO. You can have a
> `SplitCommand::command_needs_splitting` method if you want to avoid
> comparing against the const in `send_command`, but honestly I think this
> is self-documenting already - you split the command because it is larger
> than the maximum supported size of the queue.
>
> It also would have the benefit of simplifying `SplitState` and
> `SplitCommand` since they wouldn't have to handle the non-split case at
> all. Actually you could just have a method that consumes the command and
> returns a tuple with the `SplitCommand` wrapping it, and its
> continuation records. That way I suspect you also remove the need to
> pass `command` twice.

Mmm or maybe it's not that simple. I'll experiment on the rebased v3
once it it sent, please ignore this comment for now.