From: Michael Brown <mcb30@ipxe.org>
Date: Thu, 10 Jul 2025 13:33:34 +0000 (+0100)
Subject: [riscv] Invalidate data cache on completed RX DMA buffers
X-Git-Url: http://git.ipfire.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=bbabde8ff8182fcef738893c29a698783758a489;p=thirdparty%2Fipxe.git

[riscv] Invalidate data cache on completed RX DMA buffers

The data cache must be invalidated twice for RX DMA buffers: once
before passing ownership to the DMA device (in case the cache happens
to contain dirty data that will be written back at an undefined future
point), and once after receiving ownership from the DMA device (in
case the CPU happens to have speculatively accessed data in the buffer
while it was owned by the hardware).

Only the used portion of the buffer needs to be invalidated after
completion, since we do not care about data within the unused portion.

Update the DMA API to include the used length as an additional
parameter to dma_unmap(), and add the necessary second cache
invalidation pass to the RISC-V DMA API implementation.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
---

diff --git a/src/arch/riscv/core/riscv_dma.c b/src/arch/riscv/core/riscv_dma.c
index d215fba2c..ab88f2785 100644
--- a/src/arch/riscv/core/riscv_dma.c
+++ b/src/arch/riscv/core/riscv_dma.c
@@ -44,24 +44,57 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
  * @v flags		Mapping flags
  * @ret rc		Return status code
  */
-static int riscv_dma_map ( struct dma_device *dma __unused,
-			   struct dma_mapping *map __unused,
+static int riscv_dma_map ( struct dma_device *dma,
+			   struct dma_mapping *map,
 			   void *addr, size_t len, int flags ) {
 
 	/* Sanity check: we cannot support bidirectional mappings */
 	assert ( ! ( ( flags & DMA_TX ) & ( flags & DMA_RX ) ) );
 
+	/* Populate mapping */
+	map->dma = dma;
+	map->offset = 0;
+	map->token = NULL;
+
 	/* Flush cached data to transmit buffers */
 	if ( flags & DMA_TX )
 		cache_clean ( addr, len );
 
-	/* Invalidate cached data in receive buffers */
-	if ( flags & DMA_RX )
+	/* Invalidate cached data in receive buffers and record address */
+	if ( flags & DMA_RX ) {
 		cache_invalidate ( addr, len );
+		map->token = addr;
+	}
+
+	/* Increment mapping count (for debugging) */
+	if ( DBG_LOG )
+		dma->mapped++;
 
 	return 0;
 }
 
+/**
+ * Unmap buffer
+ *
+ * @v map		DMA mapping
+ * @v len		Used length
+ */
+static void riscv_dma_unmap ( struct dma_mapping *map, size_t len ) {
+	struct dma_device *dma = map->dma;
+	void *addr = map->token;
+
+	/* Invalidate cached data in receive buffers */
+	if ( addr )
+		cache_invalidate ( addr, len );
+
+	/* Clear mapping */
+	map->dma = NULL;
+
+	/* Decrement mapping count (for debugging) */
+	if ( DBG_LOG )
+		dma->mapped--;
+}
+
 /**
  * Allocate and map DMA-coherent buffer
  *
@@ -98,6 +131,10 @@ static void * riscv_dma_alloc ( struct dma_device *dma,
 	DBGC ( dma, "DMA allocated [%#08lx,%#08lx) via %p\n",
 	       phys, ( phys + len ), caddr );
 
+	/* Increment allocation count (for debugging) */
+	if ( DBG_LOG )
+		dma->allocated++;
+
 	return caddr;
 }
 
@@ -111,6 +148,7 @@ static void * riscv_dma_alloc ( struct dma_device *dma,
  */
 static void riscv_dma_free ( struct dma_mapping *map,
 			     void *addr, size_t len ) {
+	struct dma_device *dma = map->dma;
 
 	/* Sanity check */
 	assert ( virt_to_phys ( addr ) == virt_to_phys ( map->token ) );
@@ -121,10 +159,14 @@ static void riscv_dma_free ( struct dma_mapping *map,
 	/* Clear mapping */
 	map->dma = NULL;
 	map->token = NULL;
+
+	/* Decrement allocation count (for debugging) */
+	if ( DBG_LOG )
+		dma->allocated--;
 }
 
 PROVIDE_DMAAPI ( riscv, dma_map, riscv_dma_map );
-PROVIDE_DMAAPI_INLINE ( riscv, dma_unmap );
+PROVIDE_DMAAPI ( riscv, dma_unmap, riscv_dma_unmap );
 PROVIDE_DMAAPI ( riscv, dma_alloc, riscv_dma_alloc );
 PROVIDE_DMAAPI ( riscv, dma_free, riscv_dma_free );
 PROVIDE_DMAAPI ( riscv, dma_umalloc, riscv_dma_alloc );
diff --git a/src/arch/riscv/include/ipxe/riscv_dma.h b/src/arch/riscv/include/ipxe/riscv_dma.h
index 568f28afe..d35904d88 100644
--- a/src/arch/riscv/include/ipxe/riscv_dma.h
+++ b/src/arch/riscv/include/ipxe/riscv_dma.h
@@ -15,17 +15,6 @@ FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
 #define DMAAPI_PREFIX_riscv __riscv_
 #endif
 
-/**
- * Unmap buffer
- *
- * @v map		DMA mapping
- */
-static inline __always_inline void
-DMAAPI_INLINE ( riscv, dma_unmap ) ( struct dma_mapping *map __unused ) {
-
-	/* Nothing to do */
-}
-
 /**
  * Set addressable space mask
  *
diff --git a/src/core/dma.c b/src/core/dma.c
index cbc9b8d10..3f3023c4d 100644
--- a/src/core/dma.c
+++ b/src/core/dma.c
@@ -79,13 +79,14 @@ static int dma_op_map ( struct dma_device *dma, struct dma_mapping *map,
  * Unmap buffer
  *
  * @v map		DMA mapping
+ * @v len		Used length
  */
-static void dma_op_unmap ( struct dma_mapping *map ) {
+static void dma_op_unmap ( struct dma_mapping *map, size_t len ) {
 	struct dma_device *dma = map->dma;
 
 	assert ( dma != NULL );
 	assert ( dma->op != NULL );
-	dma->op->unmap ( dma, map );
+	dma->op->unmap ( dma, map, len );
 }
 
 /**
diff --git a/src/drivers/net/intelxl.c b/src/drivers/net/intelxl.c
index 1d4c22a09..31a3e2577 100644
--- a/src/drivers/net/intelxl.c
+++ b/src/drivers/net/intelxl.c
@@ -90,7 +90,7 @@ int intelxl_msix_enable ( struct intelxl_nic *intelxl,
 
 	pci_msix_disable ( pci, &intelxl->msix.cap );
  err_enable:
-	dma_unmap ( &intelxl->msix.map );
+	dma_unmap ( &intelxl->msix.map, sizeof ( intelxl->msix.msg ) );
  err_map:
 	return rc;
 }
@@ -112,7 +112,7 @@ void intelxl_msix_disable ( struct intelxl_nic *intelxl,
 	pci_msix_disable ( pci, &intelxl->msix.cap );
 
 	/* Unmap dummy target location */
-	dma_unmap ( &intelxl->msix.map );
+	dma_unmap ( &intelxl->msix.map, sizeof ( intelxl->msix.msg ) );
 }
 
 /******************************************************************************
diff --git a/src/include/ipxe/dma.h b/src/include/ipxe/dma.h
index b675df212..a6e41c1ab 100644
--- a/src/include/ipxe/dma.h
+++ b/src/include/ipxe/dma.h
@@ -74,8 +74,10 @@ struct dma_operations {
 	 *
 	 * @v dma		DMA device
 	 * @v map		DMA mapping
+	 * @v len		Used length
 	 */
-	void ( * unmap ) ( struct dma_device *dma, struct dma_mapping *map );
+	void ( * unmap ) ( struct dma_device *dma, struct dma_mapping *map,
+			   size_t len );
 	/**
 	 * Allocate and map DMA-coherent buffer
 	 *
@@ -194,9 +196,11 @@ DMAAPI_INLINE ( flat, dma_map ) ( struct dma_device *dma,
  * Unmap buffer
  *
  * @v map		DMA mapping
+ * @v len		Used length
  */
 static inline __always_inline void
-DMAAPI_INLINE ( flat, dma_unmap ) ( struct dma_mapping *map ) {
+DMAAPI_INLINE ( flat, dma_unmap ) ( struct dma_mapping *map,
+				    size_t len __unused ) {
 
 	/* Decrement mapping count (for debugging) */
 	if ( DBG_LOG ) {
@@ -365,8 +369,9 @@ int dma_map ( struct dma_device *dma, struct dma_mapping *map,
  * Unmap buffer
  *
  * @v map		DMA mapping
+ * @v len		Used length
  */
-void dma_unmap ( struct dma_mapping *map );
+void dma_unmap ( struct dma_mapping *map, size_t len );
 
 /**
  * Allocate and map DMA-coherent buffer
diff --git a/src/include/ipxe/iobuf.h b/src/include/ipxe/iobuf.h
index df8d0b854..46b350458 100644
--- a/src/include/ipxe/iobuf.h
+++ b/src/include/ipxe/iobuf.h
@@ -276,7 +276,7 @@ static inline __always_inline physaddr_t iob_dma ( struct io_buffer *iobuf ) {
  * @ret rc		Return status code
  */
 static inline __always_inline void iob_unmap ( struct io_buffer *iobuf ) {
-	dma_unmap ( &iobuf->map );
+	dma_unmap ( &iobuf->map, iob_len ( iobuf ) );
 }
 
 extern struct io_buffer * __malloc alloc_iob_raw ( size_t len, size_t align,
diff --git a/src/interface/efi/efi_pci.c b/src/interface/efi/efi_pci.c
index ae0ec4264..fbf06300b 100644
--- a/src/interface/efi/efi_pci.c
+++ b/src/interface/efi/efi_pci.c
@@ -537,9 +537,10 @@ static int efipci_dma_map ( struct dma_device *dma, struct dma_mapping *map,
  *
  * @v dma		DMA device
  * @v map		DMA mapping
+ * @v len		Used length
  */
 static void efipci_dma_unmap ( struct dma_device *dma,
-			       struct dma_mapping *map ) {
+			       struct dma_mapping *map, size_t len __unused ) {
 	struct efi_pci_device *efipci =
 		container_of ( dma, struct efi_pci_device, pci.dma );
 	EFI_PCI_IO_PROTOCOL *pci_io = efipci->io;
@@ -606,7 +607,7 @@ static void * efipci_dma_alloc ( struct dma_device *dma,
 
 	return addr;
 
-	efipci_dma_unmap ( dma, map );
+	efipci_dma_unmap ( dma, map, len );
  err_map:
 	pci_io->FreeBuffer ( pci_io, pages, addr );
  err_alloc:
@@ -632,7 +633,7 @@ static void efipci_dma_free ( struct dma_device *dma, struct dma_mapping *map,
 	pages = ( ( len + EFI_PAGE_SIZE - 1 ) / EFI_PAGE_SIZE );
 
 	/* Unmap buffer */
-	efipci_dma_unmap ( dma, map );
+	efipci_dma_unmap ( dma, map, len );
 
 	/* Free buffer */
 	pci_io->FreeBuffer ( pci_io, pages, addr );