Re: [PATCH 0/7] target/arm: Add vSPE support to KVM guest

[Haibo Xu]

On Mon, 31 Aug 2020 at 15:56, Auger Eric <eric.auger@redhat.com> wrote:
>
> Hi Haibo,
>
> On 8/7/20 10:10 AM, Haibo Xu wrote:
> > This series add support for SPE(Statistical Profiling Extension)[1]
> > in KVM guest. It's based on Andrew Murray's kernel KVM patches V2[2],
> > and has been tested to ensure that guest can use SPE with valid data.
> > E.g.
> >
> > In host:
> > $ ./qemu-system-aarch64 \
> >         -cpu host -M virt,accel=kvm,gic-version=3 -nographic -m 2048M \
> >         -kernel ./Image-new \
> >         -initrd /boot/initrd.img-5.6.0-rc2+ \
> >         -append "root=/dev/vda rw console=ttyAMA0" -nodefaults -serial 
> > stdio\
> >         -drive if=none,file=./xenial.rootfs.ext4,id=hd0,format=raw \
> >         -device virtio-blk-device,drive=hd0  \
> >
> > In guest:
> > $ perf record -e arm_spe/ts_enable=1,pa_enable=1,pct_enable=1/ \
> >         dd if=/dev/zero of=/dev/null count=1000
> > $ perf report --dump-raw-trace > spe_buf.txt
> >
> > The spe_buf.txt should contain similar data as below:
> >
> > . ... ARM SPE data: size 135944 bytes
> > .  00000000:  b0 f4 d3 29 10 00 80 ff a0                      PC 
> > 0xff80001029d3f4 el1 ns=1
> > .  00000009:  99 0b 00                                        LAT 11 ISSUE
> > .  0000000c:  98 0d 00                                        LAT 13 TOT
> > .  0000000f:  52 16 00                                        EV RETIRED 
> > L1D-ACCESS TLB-ACCESS
> > .  00000012:  49 00                                           LD
> > .  00000014:  b2 d0 40 d8 70 00 00 ff 00                      VA 
> > 0xff000070d840d0
> > .  0000001d:  9a 01 00                                        LAT 1 XLAT
> > .  00000020:  00 00 00                                        PAD
> > .  00000023:  71 a5 1f b3 20 14 00 00 00                      TS 86447955877
> > .  0000002c:  b0 7c f9 29 10 00 80 ff a0                      PC 
> > 0xff80001029f97c el1 ns=1
> > .  00000035:  99 02 00                                        LAT 2 ISSUE
> > .  00000038:  98 03 00                                        LAT 3 TOT
> > .  0000003b:  52 02 00                                        EV RETIRED
> > .  0000003e:  48 00                                           INSN-OTHER
> > .  00000040:  00 00 00                                        PAD
> > .  00000043:  71 ef 1f b3 20 14 00 00 00                      TS 86447955951
> > .  0000004c:  b0 f0 e9 29 10 00 80 ff a0                      PC 
> > 0xff80001029e9f0 el1 ns=1
> > .  00000055:  99 02 00                                        LAT 2 ISSUE
> > .  00000058:  98 03 00                                        LAT 3 TOT
> > .  0000005b:  52 02 00                                        EV RETIRED
> >
> > If you want to disable the vSPE support, you can use the 'spe=off' cpu
> > property:
> >
> > ./qemu-system-aarch64 \
> >         -cpu host,spe=off -M virt,accel=kvm,gic-version=3 -nographic -m 
> > 2048M \
> >         -kernel ./Image-new \
> >         -initrd /boot/initrd.img-5.6.0-rc2+ \
> >         -append "root=/dev/vda rw console=ttyAMA0" -nodefaults -serial 
> > stdio\
> >         -drive if=none,file=./xenial.rootfs.ext4,id=hd0,format=raw \
> >         -device virtio-blk-device,drive=hd0  \
> >
> > Note:
> > (1) Since the kernel patches are still under review, some of the macros
> >     in the header files may be changed after merging. We may need to
> >     update them accordingly.
> to be more explicit one needs to replace on the kernel 5.5-rc2 based series
>
> -#define KVM_CAP_ARM_SPE_V1 179
> +#define KVM_CAP_ARM_SPE_V1 184
>
> I got misleaded ;-)
>
> + Andrew in CC as he contributed the kernel part.
>
> For information, I have been working on a kvm unit test series for
> testing SPE. I will send an RFC, most probably this week. At the moment
> I still face some weirdness such as some unexpected Service state in the
> syndrome register. Anyway I will share the existing code so that we can
> discuss the issues.
>
> Are there any plans to respin the kernel series
>
> Thanks
>
> Eric
>

Hi Eric,

Thanks for elaborating on the above macro definition!
The next version of the kernel series are supposed to be sent out in
mid-September,
and it should not change so much except for some macro definitions.

Regards,

Haibo

> > (2) These patches only add vSPE support in KVM mode, for TCG mode, I'm
> >     not sure whether we need to support it.
> > (3) Just followed the 'pmu' property, we only allow this feature to be
> >     removed from CPUs which enable it by default. But since the SPE is
> >     an optional feature extension for Armv8.2, I think a better way may
> >     be to disable it by default, and only enable it when the host cpu
> >     do have the feature.
> >
> > [1]https://community.arm.com/developer/ip-products/processors/b/processors-ip-blog/
> >    posts/statistical-profiling-extension-for-armv8-a
> > [2]https://www.spinics.net/lists/arm-kernel/msg776228.html
> >
> > Haibo Xu (7):
> >   update Linux headers with new vSPE macros
> >   target/arm/kvm: spe: Add helper to detect SPE when using KVM
> >   target/arm/cpu: spe: Add an option to turn on/off vSPE support
> >   target/arm/kvm: spe: Unify device attr operatioin helper
> >   target/arm/kvm: spe: Add device init and set_irq operations
> >   hw/arm/virt: spe: Add SPE fdt binding for virt machine
> >   target/arm/cpu: spe: Enable spe to work with host cpu
> >
> >  hw/arm/virt-acpi-build.c      |  3 +++
> >  hw/arm/virt.c                 | 42 ++++++++++++++++++++++++++++++
> >  include/hw/acpi/acpi-defs.h   |  1 +
> >  include/hw/arm/virt.h         |  1 +
> >  linux-headers/asm-arm64/kvm.h |  4 +++
> >  linux-headers/linux/kvm.h     |  2 ++
> >  target/arm/cpu.c              | 34 +++++++++++++++++++++++++
> >  target/arm/cpu.h              |  5 ++++
> >  target/arm/kvm.c              | 11 ++++++++
> >  target/arm/kvm64.c            | 48 ++++++++++++++++++++++++++++++++---
> >  target/arm/kvm_arm.h          | 18 +++++++++++++
> >  11 files changed, 166 insertions(+), 3 deletions(-)
> >
>