Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-22 Thread Jan Beulich
On 22.05.15 at 10:25, jbeul...@suse.com wrote: On 21.05.15 at 13:48, jbeul...@suse.com wrote: On 21.05.15 at 13:08, andrew.coop...@citrix.com wrote: It might be wise to have a BUILD_BUG_ON() which confirms that STUBS_PER_PAGE is a power of two, which is a requirement given the way it is

Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-22 Thread Jan Beulich
On 21.05.15 at 13:48, jbeul...@suse.com wrote: On 21.05.15 at 13:08, andrew.coop...@citrix.com wrote: On 21/05/15 11:15, Jan Beulich wrote: This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs on the same node) instead. Stub areas

Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-22 Thread Andrew Cooper
On 22/05/2015 09:25, Jan Beulich wrote: On 21.05.15 at 13:48, jbeul...@suse.com wrote: On 21.05.15 at 13:08, andrew.coop...@citrix.com wrote: On 21/05/15 11:15, Jan Beulich wrote: This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs

Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-21 Thread Jan Beulich
On 21.05.15 at 13:08, andrew.coop...@citrix.com wrote: On 21/05/15 11:15, Jan Beulich wrote: This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs on the same node) instead. Stub areas (currently 128 bytes each) are being split into

Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-21 Thread Andrew Cooper
On 21/05/15 12:48, Jan Beulich wrote: On 21.05.15 at 13:08, andrew.coop...@citrix.com wrote: On 21/05/15 11:15, Jan Beulich wrote: This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs on the same node) instead. Stub areas

[Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-21 Thread Jan Beulich
This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs on the same node) instead. Stub areas (currently 128 bytes each) are being split into two parts - a fixed usage one (the syscall ones) and dynamically usable space, which will be used

Re: [Xen-devel] [PATCH v2 1/4] x86: move syscall trampolines off the stack

2015-05-21 Thread Andrew Cooper
On 21/05/15 11:15, Jan Beulich wrote: This is needed as stacks are going to become non-executable. Use separate stub pages (shared among suitable CPUs on the same node) instead. Stub areas (currently 128 bytes each) are being split into two parts - a fixed usage one (the syscall ones) and