On 24.11.2021 10:23, Untitled YAN wrote: > Original email: > > From: Jan Beulich <[email protected]> > Sent: Wednesday, November 24, 2021 15:54 > To: YAN Untitled <[email protected]> > Cc: [email protected] <[email protected]>; [email protected] > <[email protected]>; [email protected] > <[email protected]>; [email protected] > <[email protected]> > Subject: Re: About support for memory event on AMD CPUs > >> On 23.11.2021 18:14, YAN Untitled wrote: >>> Dear developers, >>> >>> Short version: is memory event supported on AMD CPUs or is it going to be >>> supported? >>> >>> Long version: >>> >>> Environment: LibVMI 0.15.0 + Xen 4.14.3 on an **AMD CPU** (5950x), 64-bit >>> Debian 11 Dom0. >>> >>> What I am trying to accomplish: register a **memory event** handler, so that >>> I can capture all memory accesses within a specific range issued by any >>> thread, >>> or all memory accesses within any range issued by a specific thread. >>> >>> What I got instead: an error from LibVMI saying >>> "xc_hvm_set_mem_access failed with code: -1". >>> >>> Some investigation: by inspecting the source code of LibVMI, I find the >>> direct >>> cause is one of the libxc functions, 1) xc_set_mem_access or >>> 2) xc_altp2m_set_mem_access, returned error code -1. >>> >>> After some searching, I found someone else having a similar problem [1]. I >>> also >>> noted LibVMI says: >>> >>>> Currently only the Xen Hypervisor provides these features, >>>> and some of these are specifically only available on Intel CPUs >>> >>> However, I can't find the exact confirmation for the availability of memory >>> event on AMD CPUs from https://wiki.xenproject.org. >> >> Aiui underlying what you want is altp2m, which presently depends (in >> the hypervisor) on EPT being available (and in use for the guest in >> question). >> >> Jan > > Dear Jan, > > Thanks for your reply. I really appreciate the information. After some > searching with the keyword "EPT" I found [1]. So I checked on dom0 with > "xl dmesg | grep HAP", which says: > >> (XEN) HVM: Hardware Assisted Paging (HAP) detected >> (XEN) HVM: HAP page sizes: 4kB, 2MB, 1GB > > And the guest is an HVM guest running Debian 10 with kernel v4.16 built from > source. Most of the configuration of the guest is generated by virt-manager. > The "xl list -l" shows that there is no explicit configuration for EPT, RVI or > HAP, but it does say the "type" is "hvm".
HAP is the term covering EPT on the Intel side and NPT for AMD. Jan
