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libvhost-user: Speedup gpa_to_mem_region() and vu_gpa_to_va() 

Let's speed up GPA to memory region / virtual address lookup. Store the
memory regions ordered by guest physical addresses, and use binary
search for address translation, as well as when adding/removing memory
regions.

Most importantly, this will speed up GPA->VA address translation when we
have many memslots.

Reviewed-by: Raphael Norwitz <raphael@enfabrica.net>
Acked-by: Stefano Garzarella <sgarzare@redhat.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20240214151701.29906-11-david@redhat.com>
Tested-by: Mario Casquero <mcasquer@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
David Hildenbrand 2024-02-14 16:16:57 +01:00 committed by Michael S. Tsirkin
parent 60ccdca42d
commit a3c0118c5a
1 changed files with 45 additions and 4 deletions
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49
subprojects/libvhost-user/libvhost-user.c
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@ -199,19 +199,30 @@ vu_panic(VuDev *dev, const char *msg, ...)
static VuDevRegion *
vu_gpa_to_mem_region(VuDev *dev, uint64_t guest_addr)
{
unsigned int i;
int low = 0;
int high = dev->nregions - 1;
/*
* Memory regions cannot overlap in guest physical address space. Each
* GPA belongs to exactly one memory region, so there can only be one
* match.
*
* We store our memory regions ordered by GPA and can simply perform a
* binary search.
*/
for (i = 0; i < dev->nregions; i++) {
VuDevRegion *cur = &dev->regions[i];
while (low <= high) {
unsigned int mid = low + (high - low) / 2;
VuDevRegion *cur = &dev->regions[mid];
if (guest_addr >= cur->gpa && guest_addr < cur->gpa + cur->size) {
return cur;
}
if (guest_addr >= cur->gpa + cur->size) {
low = mid + 1;
}
if (guest_addr < cur->gpa) {
high = mid - 1;
}
}
return NULL;
}
@ -273,9 +284,14 @@ vu_remove_all_mem_regs(VuDev *dev)
static void
_vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd)
{
const uint64_t start_gpa = msg_region->guest_phys_addr;
const uint64_t end_gpa = start_gpa + msg_region->memory_size;
int prot = PROT_READ | PROT_WRITE;
VuDevRegion *r;
void *mmap_addr;
int low = 0;
int high = dev->nregions - 1;
unsigned int idx;
DPRINT("Adding region %d\n", dev->nregions);
DPRINT(" guest_phys_addr: 0x%016"PRIx64"\n",
@ -295,6 +311,29 @@ _vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd)
prot = PROT_NONE;
}
/*
* We will add memory regions into the array sorted by GPA. Perform a
* binary search to locate the insertion point: it will be at the low
* index.
*/
while (low <= high) {
unsigned int mid = low + (high - low) / 2;
VuDevRegion *cur = &dev->regions[mid];
/* Overlap of GPA addresses. */
if (start_gpa < cur->gpa + cur->size && cur->gpa < end_gpa) {
vu_panic(dev, "regions with overlapping guest physical addresses");
return;
}
if (start_gpa >= cur->gpa + cur->size) {
low = mid + 1;
}
if (start_gpa < cur->gpa) {
high = mid - 1;
}
}
idx = low;
/*
* We don't use offset argument of mmap() since the mapped address has
* to be page aligned, and we use huge pages.
@ -308,7 +347,9 @@ _vu_add_mem_reg(VuDev *dev, VhostUserMemoryRegion *msg_region, int fd)
DPRINT(" mmap_addr: 0x%016"PRIx64"\n",
(uint64_t)(uintptr_t)mmap_addr);
r = &dev->regions[dev->nregions];
/* Shift all affected entries by 1 to open a hole at idx. */
r = &dev->regions[idx];
memmove(r + 1, r, sizeof(VuDevRegion) * (dev->nregions - idx));
r->gpa = msg_region->guest_phys_addr;
r->size = msg_region->memory_size;
r->qva = msg_region->userspace_addr;