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

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Date:   Thu, 16 May 2019 16:25:08 +0800
From:   Luwei Kang <luwei.kang@...el.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, hpa@...or.com,
        x86@...nel.org, pbonzini@...hat.com, rkrcmar@...hat.com,
        Luwei Kang <luwei.kang@...el.com>
Subject: [PATCH v1 0/6] KVM: VMX: Intel PT configuration switch using XSAVES/XRSTORS on VM-Entry/Exit

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(-)

-- 
1.8.3.1