Messages in this thread | | | From | KOSAKI Motohiro <> | Subject | Re: [RFC][PATCH] Cross Memory Attach | Date | Thu, 16 Sep 2010 10:58:08 +0900 (JST) |
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> On Wed, Sep 15, 2010 at 19:58, Avi Kivity <avi@redhat.com> wrote: > > > Instead of those two syscalls, how about a vmfd(pid_t pid, ulong start, > > ulong len) system call which returns an file descriptor that represents a > > portion of the process address space. You can then use preadv() and > > pwritev() to copy memory, and io_submit(IO_CMD_PREADV) and > > io_submit(IO_CMD_PWRITEV) for asynchronous variants (especially useful with > > a dma engine, since that adds latency). > > > > With some care (and use of mmu_notifiers) you can even mmap() your vmfd and > > access remote process memory directly. > > Rather than introducing a new vmfd() API for this, why not just add > implementations for these more efficient operations to the existing > /proc/$pid/mem interface?
As far as I heared from my friend, old HP MPI implementation used /proc/$pid/mem for this purpose. (I don't know current status). However almost implementation doesn't do that because /proc/$pid/mem required the process is ptraced. As far as I understand , very old /proc/$pid/mem doesn't require it. but It changed for security concern. Then, Anybody haven't want to change this interface because they worry break security.
But, I don't know what exactly protected "the process is ptraced" check. If anyone explain the reason and we can remove it. I'm not againt at all.
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