Re: [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory

[Chao Peng]

On Fri, Apr 22, 2022 at 01:06:25PM +0200, Paolo Bonzini wrote:
> On 4/22/22 12:56, Chao Peng wrote:
> >          /* memfile notifier flags */
> >          #define MFN_F_USER_INACCESSIBLE   0x0001  /* memory allocated in the file is inaccessible from userspace (e.g. read/write/mmap) */
> >          #define MFN_F_UNMOVABLE           0x0002  /* memory allocated in the file is unmovable */
> >          #define MFN_F_UNRECLAIMABLE       0x0003  /* memory allocated in the file is unreclaimable (e.g. via kswapd or any other pathes) */
> 
> You probably mean BIT(0/1/2) here.

Right, it's BIT(n), Thanks.

Chao
> 
> Paolo
> 
> >      When memfile_notifier is being registered, memfile_register_notifier will
> >      need check these flags. E.g. for MFN_F_USER_INACCESSIBLE, it fails when
> >      previous mmap-ed mapping exists on the fd (I'm still unclear on how to do
> >      this). When multiple consumers are supported it also need check all
> >      registered consumers to see if any conflict (e.g. all consumers should have
> >      MFN_F_USER_INACCESSIBLE set). Only when the register succeeds, the fd is
> >      converted into a private fd, before that, the fd is just a normal (shared)
> >      one. During this conversion, the previous data is preserved so you can put
> >      some initial data in guest pages (whether the architecture allows this is
> >      architecture-specific and out of the scope of this patch).