Re: [PATCH v5 00/13] KVM: mm: fd-based approach for supporting KVM guest private memory
From: Chao Peng
Date: Sun Apr 24 2022 - 04:11:18 EST
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.
> > 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).