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This commit is contained in:
JackDoan
2025-11-08 13:01:40 -06:00
parent edff19a05b
commit 987f45baf0
5 changed files with 42 additions and 28 deletions
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23
overlay/virtqueue/descriptor_table.go
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@@ -4,7 +4,6 @@ import (
"errors"
"fmt"
"math"
"os"
"sync"
"unsafe"
@@ -54,6 +53,7 @@ type DescriptorTable struct {
bufferBase uintptr
bufferSize int
itemSize int
mu sync.Mutex
}
@@ -63,7 +63,7 @@ type DescriptorTable struct {
// descriptor table (see [descriptorTableSize]) for the given queue size.
//
// Before this descriptor table can be used, [initialize] must be called.
func newDescriptorTable(queueSize int, mem []byte) *DescriptorTable {
func newDescriptorTable(queueSize int, mem []byte, itemSize int) *DescriptorTable {
dtSize := descriptorTableSize(queueSize)
if len(mem) != dtSize {
panic(fmt.Sprintf("memory size (%v) does not match required size "+
@@ -75,6 +75,7 @@ func newDescriptorTable(queueSize int, mem []byte) *DescriptorTable {
// We have no free descriptors until they were initialized.
freeHeadIndex: noFreeHead,
freeNum: 0,
itemSize: itemSize, //todo configurable? needs to be page-aligned
}
}
@@ -116,10 +117,8 @@ func (dt *DescriptorTable) BufferAddresses() map[uintptr]int {
func (dt *DescriptorTable) initializeDescriptors() error {
numDescriptors := len(dt.descriptors)
itemSize := os.Getpagesize() //todo configurable? needs to be page-aligned
// Allocate ONE large region for all buffers
totalSize := itemSize * numDescriptors
totalSize := dt.itemSize * numDescriptors
basePtr, err := unix.MmapPtr(-1, 0, nil, uintptr(totalSize),
unix.PROT_READ|unix.PROT_WRITE,
unix.MAP_PRIVATE|unix.MAP_ANONYMOUS)
@@ -136,7 +135,7 @@ func (dt *DescriptorTable) initializeDescriptors() error {
for i := range dt.descriptors {
dt.descriptors[i] = Descriptor{
address: dt.bufferBase + uintptr(i*itemSize),
address: dt.bufferBase + uintptr(i*dt.itemSize),
length: 0,
// All descriptors should form a free chain that loops around.
flags: descriptorFlagHasNext,
@@ -202,8 +201,6 @@ func (dt *DescriptorTable) releaseBuffers() error {
// caller should try again after some descriptor chains were used by the device
// and returned back into the free chain.
func (dt *DescriptorTable) createDescriptorChain(outBuffers [][]byte, numInBuffers int) (uint16, error) {
pageSize := os.Getpagesize()
// Calculate the number of descriptors needed to build the chain.
numDesc := uint16(len(outBuffers) + numInBuffers)
@@ -217,7 +214,7 @@ func (dt *DescriptorTable) createDescriptorChain(outBuffers [][]byte, numInBuffe
// Do we still have enough free descriptors?
if numDesc > dt.freeNum {
return 0, fmt.Errorf("%w: %d free but needed %d", ErrNotEnoughFreeDescriptors, dt.freeNum, numDesc)
return 0, ErrNotEnoughFreeDescriptors
}
// Above validation ensured that there is at least one free descriptor, so
@@ -238,16 +235,16 @@ func (dt *DescriptorTable) createDescriptorChain(outBuffers [][]byte, numInBuffe
desc := &dt.descriptors[next]
checkUnusedDescriptorLength(next, desc)
if len(buffer) > pageSize {
if len(buffer) > dt.itemSize {
// The caller should already prevent that from happening.
panic(fmt.Sprintf("out buffer %d has size %d which exceeds page size %d", i, len(buffer), pageSize))
panic(fmt.Sprintf("out buffer %d has size %d which exceeds desc length %d", i, len(buffer), dt.itemSize))
}
// Copy the buffer to the memory referenced by the descriptor.
// The descriptor address points to memory not managed by Go, so this
// conversion is safe. See https://github.com/golang/go/issues/58625
//goland:noinspection GoVetUnsafePointer
copy(unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), pageSize), buffer)
copy(unsafe.Slice((*byte)(unsafe.Pointer(desc.address)), dt.itemSize), buffer)
desc.length = uint32(len(buffer))
// Clear the flags in case there were any others set.
@@ -261,7 +258,7 @@ func (dt *DescriptorTable) createDescriptorChain(outBuffers [][]byte, numInBuffe
checkUnusedDescriptorLength(next, desc)
// Give the device the maximum available number of bytes to write into.
desc.length = uint32(pageSize)
desc.length = uint32(dt.itemSize)
// Mark the descriptor as device-writable.
desc.flags = descriptorFlagHasNext | descriptorFlagWritable