On Thu, Feb 29, 2024 at 01:36:29AM -0500,
Xiaoyao Li <xiaoyao.li@xxxxxxxxx> wrote:
> From: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
>
> When geeting KVM_EXIT_MEMORY_FAULT exit, it indicates userspace needs to
> do the memory conversion on the RAMBlock to turn the memory into desired
> attribute, i.e., private/shared.
>
> Currently only KVM_MEMORY_EXIT_FLAG_PRIVATE in flags is valid when
> KVM_EXIT_MEMORY_FAULT happens.
>
> Note, KVM_EXIT_MEMORY_FAULT makes sense only when the RAMBlock has
> guest_memfd memory backend.
>
> Note, KVM_EXIT_MEMORY_FAULT returns with -EFAULT, so special handling is
> added.
>
> When page is converted from shared to private, the original shared
> memory can be discarded via ram_block_discard_range(). Note, shared
> memory can be discarded only when it's not back'ed by hugetlb because
> hugetlb is supposed to be pre-allocated and no need for discarding.
>
> Signed-off-by: Chao Peng <chao.p.peng@xxxxxxxxxxxxxxx>
> Co-developed-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
>
> ---
> Changes in v4:
> - open-coded ram_block_discard logic;
> - change warn_report() to error_report(); (Daniel)
> ---
> accel/kvm/kvm-all.c | 94 ++++++++++++++++++++++++++++++++++++++++-----
> 1 file changed, 84 insertions(+), 10 deletions(-)
>
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index 70d482a2c936..87e4275932a7 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -2903,6 +2903,68 @@ static void kvm_eat_signals(CPUState *cpu)
> } while (sigismember(&chkset, SIG_IPI));
> }
>
> +static int kvm_convert_memory(hwaddr start, hwaddr size, bool to_private)
> +{
> + MemoryRegionSection section;
> + ram_addr_t offset;
> + MemoryRegion *mr;
> + RAMBlock *rb;
> + void *addr;
> + int ret = -1;
> +
> + if (!QEMU_PTR_IS_ALIGNED(start, qemu_host_page_size) ||
> + !QEMU_PTR_IS_ALIGNED(size, qemu_host_page_size)) {
> + return -1;
> + }
> +
> + if (!size) {
> + return -1;
> + }
> +
> + section = memory_region_find(get_system_memory(), start, size);
> + mr = section.mr;
> + if (!mr) {
> + return -1;
> + }
> +
> + if (memory_region_has_guest_memfd(mr)) {
> + if (to_private) {
> + ret = kvm_set_memory_attributes_private(start, size);
> + } else {
> + ret = kvm_set_memory_attributes_shared(start, size);
> + }
> +
> + if (ret) {
> + memory_region_unref(section.mr);
> + return ret;
> + }
> +
> + addr = memory_region_get_ram_ptr(mr) + section.offset_within_region;
> + rb = qemu_ram_block_from_host(addr, false, &offset);
> +
> + if (to_private) {
> + if (rb->page_size != qemu_host_page_size) {
> + /*
> + * shared memory is back'ed by hugetlb, which is supposed to be
> + * pre-allocated and doesn't need to be discarded
> + */
> + return 0;
The reference count leaks. Add memory_region_unref() is needed.
Otherwise looks good to me.
Reviewed-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
--
Isaku Yamahata <isaku.yamahata@xxxxxxxxxxxxxxx>
