From mboxrd@z Thu Jan 1 00:00:00 1970 From: Boris Ostrovsky Subject: Re: [PATCH v7 2/5] sysctl: Add sysctl interface for querying PCI topology Date: Fri, 24 Apr 2015 10:09:00 -0400 Message-ID: <553A4E7C.90805@oracle.com> References: <1429289966-4121-1-git-send-email-boris.ostrovsky@oracle.com> <1429289966-4121-3-git-send-email-boris.ostrovsky@oracle.com> <553611EC0200007800074107@mail.emea.novell.com> <55397047.2080101@oracle.com> <553A0AA6020000780007573E@mail.emea.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <553A0AA6020000780007573E@mail.emea.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: elena.ufimtseva@oracle.com, wei.liu2@citrix.com, ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, andrew.cooper3@citrix.com, dario.faggioli@citrix.com, ian.jackson@eu.citrix.com, xen-devel@lists.xen.org, keir@xen.org, dgdegra@tycho.nsa.gov List-Id: xen-devel@lists.xenproject.org On 04/24/2015 03:19 AM, Jan Beulich wrote: >>>> On 24.04.15 at 00:20, wrote: >> On 04/21/2015 03:01 AM, Jan Beulich wrote: >>>> + ((++dev_cnt > 0x3f) && hypercall_preempt_check()) ) >>>> + break; >>>> + } >>>> + >>>> + if ( (!ret || (ret == -ENODEV)) && >>>> + __copy_field_to_guest(u_sysctl, op, u.pcitopoinfo.first_dev) ) >>>> + ret = -EFAULT; >>>> + } >>>> + break; >>>> +#endif >>> With the continuation-less model now used I don't think it makes >>> sense to have first_dev and num_devs - for re-invocation all the >>> caller needs to do is increment the buffer pointer suitably. I.e. >>> you can get away with just a count of devices afaict. >>> >> This would require walking xc_hypercall_buffer_t->hbuf. Would something like >> >> set_xen_guest_handle_raw(sysctl..., (void *)HYPERCALL_BUFFER_AS_ARG(foo) + offset) >> >> be acceptable? I don't think I see anything better. >> >> I thought of adding set_xen_guest_handle_offset() that would look >> similar to set_xen_guest_handle() but then I felt that having this in >> API may not be a good idea since xc_hypercall_buffer_t->hbuf would end >> up pointing to memory that is not allocated for full >> xc_hypercall_buffer_t->sz. > There ought to be a way to create a guest handle from other than > the start of an allocated hypercall buffer, but that's really more a > question for the tool stack folks. Yes, this was question for toolstack people. (And my second paragraph was not stated correctly, now that I re-read it. I meant to say that my understanding is that API is expected to make all safety checks on buffers and with set_xen_guest_handle_offset() that I was picturing in my head we could pass in pretty much any pointer. I suppose we could check 'hbuf+offset < sz') -boris