Re: [PATCH v1 0/6] KVM: VMX: Intel PT configuration switch using XSAVES/XRSTORS on VM-Entry/Exit

Paolo Bonzini
2019-11-11T13:28:21Z

On 16/05/19 10:25, Luwei Kang wrote:
> This patch set is mainly used for reduce the overhead of switch
> Intel PT configuation contex on VM-Entry/Exit by XSAVES/XRSTORS
> instructions.
>
> I measured the cycles number of context witch on Manual and
> XSAVES/XRSTORES by rdtsc, and the data as below:
>
> Manual save(rdmsr): ~334 cycles
> Manual restore(wrmsr): ~1668 cycles
>
> XSAVES insturction: ~124 cycles
> XRSTORS instruction: ~378 cycles
>
> Manual: Switch the configuration by rdmsr and wrmsr instruction,
> and there have 8 registers need to be saved or restore.
> They are IA32_RTIT_OUTPUT_BASE, *_OUTPUT_MASK_PTRS,
> *_STATUS, *_CR3_MATCH, *_ADDR0_A, *_ADDR0_B,
> *_ADDR1_A, *_ADDR1_B.
> XSAVES/XRSTORS: Switch the configuration context by XSAVES/XRSTORS
> instructions. This patch set will allocate separate
> "struct fpu" structure to save host and guest PT state.
> Only a small portion of this structure will be used because
> we only save/restore PT state (not save AVX, AVX-512, MPX,
> PKRU and so on).
>
> This patch set also do some code clean e.g. patch 2 will reuse
> the fpu pt_state to save the PT configuration contex and
> patch 3 will dymamic allocate Intel PT configuration state.
>
> Luwei Kang (6):
> x86/fpu: Introduce new fpu state for Intel processor trace
> KVM: VMX: Reuse the pt_state structure for PT context
> KVM: VMX: Dymamic allocate Intel PT configuration state
> KVM: VMX: Allocate XSAVE area for Intel PT configuration
> KVM: VMX: Intel PT configration context switch using XSAVES/XRSTORS
> KVM: VMX: Get PT state from xsave area to variables
>
> arch/x86/include/asm/fpu/types.h | 13 ++
> arch/x86/kvm/vmx/nested.c | 2 +-
> arch/x86/kvm/vmx/vmx.c | 338 ++++++++++++++++++++++++++-------------
> arch/x86/kvm/vmx/vmx.h | 21 +--
> 4 files changed, 243 insertions(+), 131 deletions(-)
>

Luwei, I found I had missed this series. Can you check whether it needs
a rebase, since I don't have hardware that supports it?

Paolo