ACK: [B][SRU][PATCH 0/2] Add feature bit RDPRU on AMD

[Tim Gardner]

On 1/16/23 10:51 PM, Po-Hsu Lin wrote:
> [Impact]
> RDPRU, the Read Processor Register instruction of AMD Zen 2 processors
> is used to give access to some processor registers that are typically
> only accessible when the privilege level is zero.
> 
> rdpru test in ubuntu_kvm_unit_tests is to check if the RDPRU instruction
> can be intercepted by the Hypervisor. Without this patchset, this test
> will fail on our AMD Zen 2 system "riccioli" with:
>    FAIL: RDPRU raises #UD
> 
> [Fix]
> * fb64f293 x86/cpufeatures: Add feature bit RDPRU on AMD
> * 0cb8410b kvm: svm: Intercept RDPRU
> 
> We have these patches in newer releases already, only Bionic 4.15
> requires this fix. The first patch needs to be backported with some
> context adjustment, the second can be cherry-picked.
> 
> [Test]
> Test kernel can be found here:
> https://people.canonical.com/~phlin/kernel/lp-1968681-rdpru/
> 
> With the patched kernel, this rdpru test will pass on the target AMD
> Zen 2 system.
> $ sudo ./rdpru
> BUILD_HEAD=d6421940
> timeout -k 1s --foreground 90s /usr/bin/qemu-system-x86_64 --no-reboot \
> -nodefaults -device pc-testdev -device isa-debug-exit,iobase=0xf4,iosize=0x4 \
> -vnc none -serial stdio -device pci-testdev -machine accel=kvm -kernel \
> /tmp/tmp.XOMVxpyNnl -smp 1 -cpu max # -initrd /tmp/tmp.I2TbGXFiaZ
> enabling apic
> smp: waiting for 0 APs
> PASS: RDPRU raises #UD
> SUMMARY: 1 tests
> PASS rdpru (1 tests)
> 
> And the rdpru flag will be available in cpuinfo:
> $ grep -o rdpru /proc/cpuinfo
> rdpru
> 
> [Where problems could occur]
> This patchset will add a new feature bit RDPRU for AMD Zen 2. We can
> expect to see new issues coming up when using this bit in the future.
> 
> Babu Moger (1):
>    x86/cpufeatures: Add feature bit RDPRU on AMD
> 
> Jim Mattson (1):
>    kvm: svm: Intercept RDPRU
> 
>   arch/x86/include/asm/cpufeatures.h | 1 +
>   arch/x86/include/asm/svm.h         | 1 +
>   arch/x86/include/uapi/asm/svm.h    | 1 +
>   arch/x86/kvm/svm.c                 | 8 ++++++++
>   4 files changed, 11 insertions(+)
> 
Acked-by: Tim Gardner <tim.gardner at canonical.com>
-- 
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Tim Gardner
Canonical, Inc