Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-11 Thread Julien Grall
Hi Juergen, On 03/02/2018 05:25 PM, Juergen Gross wrote: On 02/03/18 18:09, Andrew Cooper wrote: On 02/03/18 17:05, Juergen Gross wrote: On 02/03/18 17:51, Jan Beulich wrote: On 02.03.18 at 17:25, wrote: On 02/03/18 16:18, Jan Beulich wrote: On 02.03.18 at 17:04, wrote: The proper way to

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-11 Thread Julien Grall
Hi Andrew, On 03/02/2018 05:09 PM, Andrew Cooper wrote: On 02/03/18 17:05, Juergen Gross wrote: On 02/03/18 17:51, Jan Beulich wrote: On 02.03.18 at 17:25, wrote: On 02/03/18 16:18, Jan Beulich wrote: On 02.03.18 at 17:04, wrote: The proper way to do this is indeed by a nominated (guest)

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Juergen Gross
On 02/03/18 18:09, Andrew Cooper wrote: > On 02/03/18 17:05, Juergen Gross wrote: >> On 02/03/18 17:51, Jan Beulich wrote: >> On 02.03.18 at 17:25, wrote: On 02/03/18 16:18, Jan Beulich wrote: On 02.03.18 at 17:04, wrote: >> The proper way to do this is indeed by a nominated

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Andrew Cooper
On 02/03/18 17:05, Juergen Gross wrote: > On 02/03/18 17:51, Jan Beulich wrote: > On 02.03.18 at 17:25, wrote: >>> On 02/03/18 16:18, Jan Beulich wrote: >>> On 02.03.18 at 17:04, wrote: > The proper way to do this is indeed by a nominated (guest) physical > address, at which point

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Juergen Gross
On 02/03/18 17:51, Jan Beulich wrote: On 02.03.18 at 17:25, wrote: >> On 02/03/18 16:18, Jan Beulich wrote: >> On 02.03.18 at 17:04, wrote: The proper way to do this is indeed by a nominated (guest) physical address, at which point Xen can make all/any updates at times of its >

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Juergen Gross
On 02/03/18 17:25, Julien Grall wrote: > > > On 02/03/18 16:18, Jan Beulich wrote: > On 02.03.18 at 17:04, wrote: >>> The proper way to do this is indeed by a nominated (guest) physical >>> address, at which point Xen can make all/any updates at times of its >>> choosing, and the guests page

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Jan Beulich
>>> On 02.03.18 at 17:25, wrote: > On 02/03/18 16:18, Jan Beulich wrote: > On 02.03.18 at 17:04, wrote: >>> The proper way to do this is indeed by a nominated (guest) physical >>> address, at which point Xen can make all/any updates at times of its >>> choosing, and the guests pagetable/permi

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Julien Grall
On 02/03/18 16:18, Jan Beulich wrote: On 02.03.18 at 17:04, wrote: The proper way to do this is indeed by a nominated (guest) physical address, at which point Xen can make all/any updates at times of its choosing, and the guests pagetable/permissions state at an instantaneous moment don't mat

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Andrew Cooper
On 02/03/18 16:18, Jan Beulich wrote: On 02.03.18 at 17:04, wrote: >> The proper way to do this is indeed by a nominated (guest) physical >> address, at which point Xen can make all/any updates at times of its >> choosing, and the guests pagetable/permissions state at an instantaneous >> mome

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Jan Beulich
>>> On 02.03.18 at 17:04, wrote: > The proper way to do this is indeed by a nominated (guest) physical > address, at which point Xen can make all/any updates at times of its > choosing, and the guests pagetable/permissions state at an instantaneous > moment don't matter. > > If you've got time to

Re: [Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Andrew Cooper
On 02/03/18 15:57, Julien Grall wrote: > Hi, > > While I was looking at some unrelated problem with Xen ARM P2M code, I > noticed that the function update_runstate_area is using guest virtual > address to update the vCPU runstate. That function will be called when > context switch to a vCPU. Howeve

[Xen-devel] update_runstate_area and Linux KPTI

2018-03-02 Thread Julien Grall
Hi, While I was looking at some unrelated problem with Xen ARM P2M code, I noticed that the function update_runstate_area is using guest virtual address to update the vCPU runstate. That function will be called when context switch to a vCPU. However, that vCPU may run in userspace context. Wh