Re: [PATCH v5 0/8] mulate Intel RDT features needed to mount ResCtrl in Linux

["Michael S. Tsirkin" <mst@redhat.com>]

On Fri, Dec 13, 2024 at 05:26:37PM +0000, Hendrik Wuethrich wrote:
> From: Hendrik Wüthrich <whendrik@google.com>
> 
> The aim of this patch series is to emulate Intel RDT features in order
> to make testing of the linux Resctrl subsystem possible with Qemu.
> 
> A branch with the patches applied can be found at:
> https://github.com/Gray-Colors/Intel_RDT_patches_applied/tree/rdt_v5
> 
> The changes made introduce the following features:



There was just my minor comment, are you going to post v6?

> * Feature enumeration for Intel RDT allocation.
> * Feature enumeration for Intel RDT monitoring.
> * Intel RDT monitoring system interface.
> * Intel RDT allocation system interface.
> 
> By adding these features, a barebones implementation most of the RDT
> state and MSRs is introduced, which can be enabled through qemu
> command line flags.
> The features missing for a faithful recreation of RDT are CDP and
> non-linear MBA throttle, as well as the possibility to configure
> various values through the command line, as some properties can be
> different across different machines. For increased ease of use, the
> correct features should be automatically enabled on machines that
> support RDT functionality.
> The missing features mentioned above will be implemented in the
> following order:
> 
> * Expand feature set for RDT allocation to include CDP and non-linear
>  MBA throttle
> * Allow for command line configuration of some values, such as the L3
>  CBM length
> * Automatically enable RDT on machines that officially support it.
> 
> Will NOT be implemented
> * Tests to simulate interaction with the host by the guest
> 
> Command line examples assuming entire patch series is applied (This
> requires a kernel with Resctrl enabled):
> 
> To emulate Intel RDT features:
> 
> Currently, it is necessary to force the RDT options on in qemu, as it is
> not automatically enabled for any machines. An example would be the
> following:
> -cpu Skylake-Server,+l3-cmt,+rdt-m,+rdt-a,+mba,+l3-cat,+l2-cat
> and
> -device rdt
> 
> Just enabling RDT in qemu won't really help, though. The following
> option allows resctrl in the kernel:
> - Kernel options: rdt=mbmlocal,mbmtotal,cmt,mba,l2cat,l3cat
> 
> To use Resctrl in the Qemu, please refer to:
> https://docs.kernel.org/arch/x86/resctrl.html
> 
> V4 -> V5
> - rebase
> - fix feature bit names to all be in hex
> 
> ‪Hendrik Wüthrich (8):
>   i386: Add Intel RDT device and State to config.
>   i386: Add init and realize functionality for RDT device.
>   i386: Add RDT functionality
>   i386: Add RDT device interface through MSRs
>   i386: Add CPUID enumeration for RDT
>   i386: Add RDT feature flags.
>   i386/cpu: Adjust CPUID level for RDT features
>   i386/cpu: Adjust level for RDT on full_cpuid_auto_level
> 
>  hw/i386/Kconfig                      |   4 +
>  hw/i386/meson.build                  |   1 +
>  hw/i386/rdt.c                        | 286 +++++++++++++++++++++++++++
>  include/hw/i386/rdt.h                |  76 +++++++
>  target/i386/cpu.c                    | 114 ++++++++++-
>  target/i386/cpu.h                    |  24 +++
>  target/i386/tcg/sysemu/misc_helper.c |  81 ++++++++
>  7 files changed, 584 insertions(+), 2 deletions(-)
>  create mode 100644 hw/i386/rdt.c
>  create mode 100644 include/hw/i386/rdt.h
> 
> -- 
> 2.47.1.613.gc27f4b7a9f-goog