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". So I am still quite confusing: 1. Is memory event feature for AMD's RVI is even implemented? 2. If memory event should be working on AMD CPUs with RVI enabled, am I missing any essential step to make it work? [1] https://groups.google.com/g/vmitools/c/JRN11E64BNY Untitled YAN
