Re: [iovisor-dev] Accessing user memory and minor page faults

2017-10-09 Thread Gianluca Borello via iovisor-dev
On Fri, Oct 6, 2017 at 3:11 AM, Alexei Starovoitov wrote: > > not following why all fs-es need to be patched. > can we do a mini version of filemap_fault() that only operates > on pages in cache? We cannot serve major faults anyway and real > fs access is not

Re: [iovisor-dev] Accessing user memory and minor page faults

2017-10-05 Thread Alexei Starovoitov via iovisor-dev
On Mon, Oct 02, 2017 at 07:29:51PM -0700, Gianluca Borello via iovisor-dev wrote: > On Sun, Oct 1, 2017 at 7:00 PM, Alexei Starovoitov > wrote: > > > > my understanding of speculative page fault patch is that the whole > > get_user_pages will operate under srcu, so

Re: [iovisor-dev] Accessing user memory and minor page faults

2017-10-02 Thread Gianluca Borello via iovisor-dev
On Sun, Oct 1, 2017 at 7:00 PM, Alexei Starovoitov wrote: > > my understanding of speculative page fault patch is that the whole > get_user_pages will operate under srcu, so we can call it > if necessary (not only find_vma will be safe to call). > Hi Alexei, My

Re: [iovisor-dev] Accessing user memory and minor page faults

2017-10-01 Thread Alexei Starovoitov via iovisor-dev
On Sun, Oct 01, 2017 at 02:08:36PM -0700, Gianluca Borello via iovisor-dev wrote: > On Mon, Sep 25, 2017 at 9:36 AM, Alexei Starovoitov > wrote: > > > > this issue was discussed at Plumbers and it seems there may be > > a solution in sight. The work on 'speculative

Re: [iovisor-dev] Accessing user memory and minor page faults

2017-09-07 Thread Gianluca Borello via iovisor-dev
On Tue, Sep 5, 2017 at 7:29 PM, Alexei Starovoitov wrote: > > thank you for the excellent summary of the problem. Thank you Alexei for your thoughtful reply and sorry for the delay, but you gave me a lot to think about :) > Do you think adding new read helper that

Re: [iovisor-dev] Accessing user memory and minor page faults

2017-09-05 Thread Alexei Starovoitov via iovisor-dev
On Thu, Aug 31, 2017 at 01:41:11PM -0700, Gianluca Borello via iovisor-dev wrote: > Hi > > I wanted to share my recent experience with troubles accessing user memory > when page faults occur, and ask for opinions. > > A bit of introduction first. It's no surprise that a very good portion of >

[iovisor-dev] Accessing user memory and minor page faults

2017-08-31 Thread Gianluca Borello via iovisor-dev
Hi I wanted to share my recent experience with troubles accessing user memory when page faults occur, and ask for opinions. A bit of introduction first. It's no surprise that a very good portion of the tracers out there vastly leverage the ability to dereference user memory for different