On Fri, Jun 24, 2016 at 8:10 PM, Tamas K Lengyel <ta...@tklengyel.com> wrote:
> > On Jun 24, 2016 05:19, "Razvan Cojocaru" <rcojoc...@bitdefender.com> > wrote: > > > > On 06/24/2016 02:05 PM, George Dunlap wrote: > > > On Wed, Jun 22, 2016 at 12:38 PM, sepanta s <sapanta...@gmail.com> > wrote: > > >> Hi, > > >> Is it possible to monitor the access on the pages withp2m_type_t > > >> p2m_ram_shared? > > > > > > cc'ing Tamas and Razvan > > > > Thanks for the CC. Judging by the "if ( npfec.write_access && (p2mt == > > p2m_ram_shared) )" line in hvm_hap_nested_page_fault() (from > > xen/arch/x86/hvm/hvm.c), I'd say it certainly looks possible. But I > > don't know what the context of the question is. > > > > > > Thanks, > > Razvan > The question is just getting the gfn and mfn of the page which is as type: p2m_ram_shared to see which pages are written and unshared. > Yes, p2m_ram_shared type pages can be monitored with mem_access just as > normal pages. The only part that may be tricky is if you map the page into > your monitoring application while the page is shared. Your handle will > continue to be valid even if the page is unshared but it will continue to > point to the shared page. However, even if you catch write access events to > the shared page that will lead to unsharing, the mem_access notification is > sent before unsharing. I just usually do unsharing myself in the mem_access > callback manually for monitored pages for this reason. I might change the > flow in 4.8 to send the notification after the unsharing happened to > simplify this. > > Tamas > Thanks, but in mem_access , what APIs can be used to see such events ?
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