From c3ec57e495b032047ddfef2075792340c407532a Mon Sep 17 00:00:00 2001 From: Mattias Nissler Date: Tue, 10 Sep 2024 14:35:12 -0700 Subject: [PATCH] softmmu: Expand comments describing max_bounce_buffer_size Clarify how the parameter gets configured and how it is used when servicing DMA mapping requests targeting indirect memory regions. Signed-off-by: Mattias Nissler Message-Id: <20240910213512.843130-1-mnissler@rivosinc.com> Acked-by: Peter Xu Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- include/exec/memory.h | 9 ++++++++- include/hw/pci/pci_device.h | 6 +++++- 2 files changed, 13 insertions(+), 2 deletions(-) diff --git a/include/exec/memory.h b/include/exec/memory.h index e5e865d1a9..9458e2801d 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -1104,7 +1104,14 @@ struct AddressSpace { QTAILQ_HEAD(, MemoryListener) listeners; QTAILQ_ENTRY(AddressSpace) address_spaces_link; - /* Maximum DMA bounce buffer size used for indirect memory map requests */ + /* + * Maximum DMA bounce buffer size used for indirect memory map requests. + * This limits the total size of bounce buffer allocations made for + * DMA requests to indirect memory regions within this AddressSpace. DMA + * requests that exceed the limit (e.g. due to overly large requested size + * or concurrent DMA requests having claimed too much buffer space) will be + * rejected and left to the caller to handle. + */ size_t max_bounce_buffer_size; /* Total size of bounce buffers currently allocated, atomically accessed */ size_t bounce_buffer_size; diff --git a/include/hw/pci/pci_device.h b/include/hw/pci/pci_device.h index 91df40f989..8eaf0d58bb 100644 --- a/include/hw/pci/pci_device.h +++ b/include/hw/pci/pci_device.h @@ -168,7 +168,11 @@ struct PCIDevice { char *failover_pair_id; uint32_t acpi_index; - /* Maximum DMA bounce buffer size used for indirect memory map requests */ + /* + * Indirect DMA region bounce buffer size as configured for the device. This + * is a configuration parameter that is reflected into bus_master_as when + * realizing the device. + */ uint32_t max_bounce_buffer_size; };