From 32e2b6a118474dbaaf7efe1f7e477e1a7b6a5a84 Mon Sep 17 00:00:00 2001
From: Michael Lotz <mmlr@mlotz.ch>
Date: Sun, 11 Oct 2009 16:49:44 +0000
Subject: [PATCH] Provide a way to directly request virtual vecs from an
 IOBuffer. If the buffer is virtual already it just returns the vecs directly,
 if it is physical it takes over the task of virtualizing the vecs either
 using vm_map_physical_memory_vecs, if there are multiple vecs or more than
 one page, or falls back to page wise mapping if mapping fails or is not
 needed. In the best case, scattered physical pages are mapped into one linear
 virtual buffer so that subsystems operating on virtual memory only get a
 single vector and can then burst read/write.

git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@33524 a95241bf-73f2-0310-859d-f6bbb57e9c96
---
 .../kernel/device_manager/IORequest.cpp       | 96 +++++++++++++++++++
 src/system/kernel/device_manager/IORequest.h  |  4 +
 2 files changed, 100 insertions(+)

diff --git a/src/system/kernel/device_manager/IORequest.cpp b/src/system/kernel/device_manager/IORequest.cpp
index 985e70f3db..24f50eae6f 100644
--- a/src/system/kernel/device_manager/IORequest.cpp
+++ b/src/system/kernel/device_manager/IORequest.cpp
@@ -15,6 +15,7 @@
 #include <thread.h>
 #include <util/AutoLock.h>
 #include <vm.h>
+#include <vm_address_space.h>
 
 #include "dma_resources.h"
 
@@ -65,6 +66,15 @@ IORequestChunk::operator delete(void* address, size_t size)
 //	#pragma mark -
 
 
+struct virtual_vec_cookie {
+	uint32	vec_index;
+	size_t	vec_offset;
+	area_id	mapped_area;
+	void*	physical_page_handle;
+	addr_t	virtual_address;
+};
+
+
 IOBuffer*
 IOBuffer::Create(uint32 count, bool vip)
 {
@@ -115,6 +125,92 @@ IOBuffer::SetVecs(size_t firstVecOffset, const iovec* vecs, uint32 count,
 }
 
 
+status_t
+IOBuffer::GetNextVirtualVec(void*& _cookie, iovec& vector)
+{
+	virtual_vec_cookie* cookie = (virtual_vec_cookie*)_cookie;
+	if (cookie == NULL) {
+		cookie = new(std::nothrow) virtual_vec_cookie;
+		if (cookie == NULL)
+			return B_NO_MEMORY;
+
+		cookie->vec_index = 0;
+		cookie->vec_offset = 0;
+		cookie->mapped_area = -1;
+		cookie->physical_page_handle = NULL;
+		cookie->virtual_address = 0;
+		_cookie = cookie;
+	}
+
+	// recycle a potential previously mapped page
+	if (cookie->physical_page_handle != NULL) {
+		vm_put_physical_page(cookie->virtual_address,
+			cookie->physical_page_handle);
+	}
+
+	if (cookie->vec_index >= fVecCount)
+		return B_BAD_INDEX;
+
+	if (!fPhysical) {
+		vector = fVecs[cookie->vec_index++];
+		return B_OK;
+	}
+
+	if (cookie->vec_index == 0
+		&& (fVecCount > 1 || fVecs[0].iov_len > B_PAGE_SIZE)) {
+		void* mappedAddress;
+		addr_t mappedSize;
+
+		cookie->mapped_area = vm_map_physical_memory_vecs(
+			vm_kernel_address_space_id(), "io buffer mapped physical vecs",
+			&mappedAddress, B_ANY_KERNEL_ADDRESS, &mappedSize,
+			B_KERNEL_READ_AREA | B_KERNEL_WRITE_AREA, fVecs, fVecCount);
+
+		if (cookie->mapped_area >= 0) {
+			vector.iov_base = (void*)mappedAddress;
+			vector.iov_len = mappedSize;
+			return B_OK;
+		} else
+			ktrace_printf("failed to map area: %s\n", strerror(cookie->mapped_area));
+	}
+
+	// fallback to page wise mapping
+	iovec& currentVec = fVecs[cookie->vec_index];
+	addr_t address = (addr_t)currentVec.iov_base + cookie->vec_offset;
+	addr_t pageOffset = address % B_PAGE_SIZE;
+
+	status_t result = vm_get_physical_page(address - pageOffset,
+		&cookie->virtual_address, &cookie->physical_page_handle);
+	if (result != B_OK)
+		return result;
+
+	size_t length = min_c(currentVec.iov_len - cookie->vec_offset,
+		B_PAGE_SIZE - pageOffset);
+
+	vector.iov_base = (void*)(cookie->virtual_address + pageOffset);
+	vector.iov_len = length;
+
+	cookie->vec_offset += length;
+	if (cookie->vec_offset >= currentVec.iov_len) {
+		cookie->vec_index++;
+		cookie->vec_offset = 0;
+	}
+
+	return B_OK;
+}
+
+
+void
+IOBuffer::FreeVirtualVecCookie(void* _cookie)
+{
+	virtual_vec_cookie* cookie = (virtual_vec_cookie*)_cookie;
+	if (cookie->mapped_area >= 0)
+		delete_area(cookie->mapped_area);
+
+	delete cookie;
+}
+
+
 status_t
 IOBuffer::LockMemory(team_id team, bool isWrite)
 {
diff --git a/src/system/kernel/device_manager/IORequest.h b/src/system/kernel/device_manager/IORequest.h
index 6df985d399..bb6f90a42d 100644
--- a/src/system/kernel/device_manager/IORequest.h
+++ b/src/system/kernel/device_manager/IORequest.h
@@ -55,6 +55,10 @@ public:
 			size_t				VecCount() const { return fVecCount; }
 			size_t				Capacity() const { return fCapacity; }
 
+			status_t			GetNextVirtualVec(void*& cookie,
+									iovec& vector);
+			void				FreeVirtualVecCookie(void* cookie);
+
 			status_t			LockMemory(team_id team, bool isWrite);
 			void				UnlockMemory(team_id team, bool isWrite);
 			bool				IsMemoryLocked() const