Re: [RFC PATCH 15/19] kvm: handle KVM_EXIT_MEMORY_FAULT

[Isaku Yamahata]

On Mon, Jul 31, 2023 at 12:21:57PM -0400,
Xiaoyao Li <xiaoyao.li@intel.com> wrote:

> From: Chao Peng <chao.p.peng@linux.intel.com>
> 
> Currently only KVM_MEMORY_EXIT_FLAG_PRIVATE in flags is valid when
> KVM_EXIT_MEMORY_FAULT happens. It indicates userspace needs to do
> the memory conversion on the RAMBlock to turn the memory into desired
> attribute, i.e., private/shared.
> 
> Note, KVM_EXIT_MEMORY_FAULT makes sense only when the RAMBlock has
> gmem memory backend.
> 
> Signed-off-by: Chao Peng <chao.p.peng@linux.intel.com>
> Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
> ---
>  accel/kvm/kvm-all.c | 52 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 52 insertions(+)
> 
> diff --git a/accel/kvm/kvm-all.c b/accel/kvm/kvm-all.c
> index f9b5050b8885..72d50b923bf2 100644
> --- a/accel/kvm/kvm-all.c
> +++ b/accel/kvm/kvm-all.c
> @@ -3040,6 +3040,48 @@ 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;
> +    void *addr;
> +    RAMBlock *rb;
> +    ram_addr_t offset;
> +    int ret = -1;
> +
> +    section = memory_region_find(get_system_memory(), start, size);
> +    if (!section.mr) {
> +        return ret;
> +    }
> +
> +    if (memory_region_can_be_private(section.mr)) {
> +        if (to_private) {
> +            ret = kvm_set_memory_attributes_private(start, size);
> +        } else {
> +            ret = kvm_set_memory_attributes_shared(start, size);
> +        }
> +
> +        if (ret) {
> +            return ret;
> +        }
> +
> +        addr = memory_region_get_ram_ptr(section.mr) +
> +               section.offset_within_region;
> +        rb = qemu_ram_block_from_host(addr, false, &offset);

Here we have already section. section.mr->ram_block.  We don't have to
scan the existing RAMBlocks.

Except that, looks good to me.
Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
-- 
Isaku Yamahata <isaku.yamahata@gmail.com>