Re: [PATCH] drivers/virt: vmgenid: add vm generation id driver

2020-10-17 Thread Colm MacCarthaigh
On 17 Oct 2020, at 6:24, Jason A. Donenfeld wrote: There are a few design goals of notifying userspace: it should be fast, because people who are using userspace RNGs are usually doing so in the first place to completely avoid syscall overhead for whatever high performance application they

Re: [PATCH] drivers/virt: vmgenid: add vm generation id driver

2020-10-17 Thread Colm MacCarthaigh
On 16 Oct 2020, at 21:02, Jann Horn wrote: On Sat, Oct 17, 2020 at 5:36 AM Willy Tarreau wrote: But in userspace, we just need a simple counter. There's no need for us to worry about anything else, like timestamps or whatever. If we repeatedly fork a paused VM, the forked VMs will see the

Re: [PATCH] drivers/virt: vmgenid: add vm generation id driver

2020-10-17 Thread Colm MacCarthaigh
On 16 Oct 2020, at 22:01, Jann Horn wrote: On Sat, Oct 17, 2020 at 6:34 AM Colm MacCarthaigh wrote: For user-space, even a single bit would do. We added MADVISE_WIPEONFORK so that userspace libraries can detect fork()/clone() robustly, for the same reasons. It just wipes a page