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

Luwei Kang
2019-05-16T08:26:41Z

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(-)

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1.8.3.1