Re: [PATCH 1/7] memory: Export a helper to get intersection of a MemoryRegionSection with a given range

Alexey Kardashevskiy
2025-01-08T04:47:45Z

On 13/12/24 18:08, Chenyi Qiang wrote:
> Rename the helper to memory_region_section_intersect_range() to make it
> more generic.
>
> Signed-off-by: Chenyi Qiang <chenyi.qiang@intel.com>
> ---
> hw/virtio/virtio-mem.c | 32 +++++---------------------------
> include/exec/memory.h | 13 +++++++++++++
> system/memory.c | 17 +++++++++++++++++
> 3 files changed, 35 insertions(+), 27 deletions(-)
>
> diff --git a/hw/virtio/virtio-mem.c b/hw/virtio/virtio-mem.c
> index 80ada89551..e3d1ccaeeb 100644
> --- a/hw/virtio/virtio-mem.c
> +++ b/hw/virtio/virtio-mem.c
> @@ -242,28 +242,6 @@ static int virtio_mem_for_each_plugged_range(VirtIOMEM *vmem, void *arg,
> return ret;
> }
>
> -/*
> - * Adjust the memory section to cover the intersection with the given range.
> - *
> - * Returns false if the intersection is empty, otherwise returns true.
> - */
> -static bool virtio_mem_intersect_memory_section(MemoryRegionSection *s,
> - uint64_t offset, uint64_t size)
> -{
> - uint64_t start = MAX(s->offset_within_region, offset);
> - uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
> - offset + size);
> -
> - if (end <= start) {
> - return false;
> - }
> -
> - s->offset_within_address_space += start - s->offset_within_region;
> - s->offset_within_region = start;
> - s->size = int128_make64(end - start);
> - return true;
> -}
> -
> typedef int (*virtio_mem_section_cb)(MemoryRegionSection *s, void *arg);
>
> static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
> @@ -285,7 +263,7 @@ static int virtio_mem_for_each_plugged_section(const VirtIOMEM *vmem,
> first_bit + 1) - 1;
> size = (last_bit - first_bit + 1) * vmem->block_size;
>
> - if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
> + if (!memory_region_section_intersect_range(&tmp, offset, size)) {
> break;
> }
> ret = cb(&tmp, arg);
> @@ -317,7 +295,7 @@ static int virtio_mem_for_each_unplugged_section(const VirtIOMEM *vmem,
> first_bit + 1) - 1;
> size = (last_bit - first_bit + 1) * vmem->block_size;
>
> - if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
> + if (!memory_region_section_intersect_range(&tmp, offset, size)) {
> break;
> }
> ret = cb(&tmp, arg);
> @@ -353,7 +331,7 @@ static void virtio_mem_notify_unplug(VirtIOMEM *vmem, uint64_t offset,
> QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
> MemoryRegionSection tmp = *rdl->section;
>
> - if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
> + if (!memory_region_section_intersect_range(&tmp, offset, size)) {
> continue;
> }
> rdl->notify_discard(rdl, &tmp);
> @@ -369,7 +347,7 @@ static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
> QLIST_FOREACH(rdl, &vmem->rdl_list, next) {
> MemoryRegionSection tmp = *rdl->section;
>
> - if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
> + if (!memory_region_section_intersect_range(&tmp, offset, size)) {
> continue;
> }
> ret = rdl->notify_populate(rdl, &tmp);
> @@ -386,7 +364,7 @@ static int virtio_mem_notify_plug(VirtIOMEM *vmem, uint64_t offset,
> if (rdl2 == rdl) {
> break;
> }
> - if (!virtio_mem_intersect_memory_section(&tmp, offset, size)) {
> + if (!memory_region_section_intersect_range(&tmp, offset, size)) {
> continue;
> }
> rdl2->notify_discard(rdl2, &tmp);
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index e5e865d1a9..ec7bc641e8 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -1196,6 +1196,19 @@ MemoryRegionSection *memory_region_section_new_copy(MemoryRegionSection *s);
> */
> void memory_region_section_free_copy(MemoryRegionSection *s);
>
> +/**
> + * memory_region_section_intersect_range: Adjust the memory section to cover
> + * the intersection with the given range.
> + *
> + * @s: the #MemoryRegionSection to be adjusted
> + * @offset: the offset of the given range in the memory region
> + * @size: the size of the given range
> + *
> + * Returns false if the intersection is empty, otherwise returns true.
> + */
> +bool memory_region_section_intersect_range(MemoryRegionSection *s,
> + uint64_t offset, uint64_t size);
> +
> /**
> * memory_region_init: Initialize a memory region
> *
> diff --git a/system/memory.c b/system/memory.c
> index 85f6834cb3..ddcec90f5e 100644
> --- a/system/memory.c
> +++ b/system/memory.c
> @@ -2898,6 +2898,23 @@ void memory_region_section_free_copy(MemoryRegionSection *s)
> g_free(s);
> }
>
> +bool memory_region_section_intersect_range(MemoryRegionSection *s,
> + uint64_t offset, uint64_t size)
> +{
> + uint64_t start = MAX(s->offset_within_region, offset);
> + uint64_t end = MIN(s->offset_within_region + int128_get64(s->size),
> + offset + size);

imho @end needs to be Int128 and s/MIN/int128_min/, etc to be totally
correct (although it is going to look horrendous). May be it was alright
when it was just virtio but now it is a wider API. I understand this is
cut-n-paste and unlikely scenario of offset+size crossing 1<<64 but
still. Thanks,

> +
> + if (end <= start) {
> + return false;
> + }
> +
> + s->offset_within_address_space += start - s->offset_within_region;
> + s->offset_within_region = start;
> + s->size = int128_make64(end - start);
> + return true;
> +}
> +
> bool memory_region_present(MemoryRegion *container, hwaddr addr)
> {
> MemoryRegion *mr;

--
Alexey