In case of a nested page fault or an intercepted #PF newer SVM implementations provide a copy of the faulting instruction bytes in the VMCB. Use these bytes to feed the instruction emulator and avoid the costly guest instruction fetch in this case.
Signed-off-by: Andre Przywara <[email protected]> --- arch/x86/include/asm/kvm_host.h | 3 +++ arch/x86/include/asm/svm.h | 4 +++- arch/x86/kvm/emulate.c | 1 + arch/x86/kvm/svm.c | 20 ++++++++++++++++++++ arch/x86/kvm/vmx.c | 7 +++++++ 5 files changed, 34 insertions(+), 1 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 2b89195..baaf063 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -586,6 +586,9 @@ struct kvm_x86_ops { void (*write_tsc_offset)(struct kvm_vcpu *vcpu, u64 offset); void (*get_exit_info)(struct kvm_vcpu *vcpu, u64 *info1, u64 *info2); + + int (*prefetch_instruction)(struct kvm_vcpu *vcpu); + const struct trace_print_flags *exit_reasons_str; }; diff --git a/arch/x86/include/asm/svm.h b/arch/x86/include/asm/svm.h index 589fc25..6d64b1d 100644 --- a/arch/x86/include/asm/svm.h +++ b/arch/x86/include/asm/svm.h @@ -81,7 +81,9 @@ struct __attribute__ ((__packed__)) vmcb_control_area { u64 lbr_ctl; u64 reserved_5; u64 next_rip; - u8 reserved_6[816]; + u8 insn_len; + u8 insn_bytes[15]; + u8 reserved_6[800]; }; diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 6366735..70385ee 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -2623,6 +2623,7 @@ x86_decode_insn(struct x86_emulate_ctxt *ctxt) c->eip = ctxt->eip; c->fetch.start = c->fetch.end = c->eip; ctxt->cs_base = seg_base(ctxt, ops, VCPU_SREG_CS); + kvm_x86_ops->prefetch_instruction(ctxt->vcpu); switch (mode) { case X86EMUL_MODE_REAL: diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index 73f1a6d..685b264 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -464,6 +464,24 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) svm_set_interrupt_shadow(vcpu, 0); } +static int svm_prefetch_instruction(struct kvm_vcpu *vcpu) +{ + struct vcpu_svm *svm = to_svm(vcpu); + uint8_t len; + struct fetch_cache *fetch; + + len = svm->vmcb->control.insn_len & 0x0F; + if (len == 0) + return 1; + + fetch = &svm->vcpu.arch.emulate_ctxt.decode.fetch; + fetch->start = kvm_rip_read(&svm->vcpu); + fetch->end = fetch->start + len; + memcpy(fetch->data, svm->vmcb->control.insn_bytes, len); + + return 0; +} + static void svm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr, bool has_error_code, u32 error_code, bool reinject) @@ -3848,6 +3866,8 @@ static struct kvm_x86_ops svm_x86_ops = { .adjust_tsc_offset = svm_adjust_tsc_offset, .set_tdp_cr3 = set_tdp_cr3, + + .prefetch_instruction = svm_prefetch_instruction, }; static int __init svm_init(void) diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c index e5ef924..7572751 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -1009,6 +1009,11 @@ static void skip_emulated_instruction(struct kvm_vcpu *vcpu) vmx_set_interrupt_shadow(vcpu, 0); } +static int vmx_prefetch_instruction(struct kvm_vcpu *vcpu) +{ + return 1; +} + static void vmx_queue_exception(struct kvm_vcpu *vcpu, unsigned nr, bool has_error_code, u32 error_code, bool reinject) @@ -4362,6 +4367,8 @@ static struct kvm_x86_ops vmx_x86_ops = { .adjust_tsc_offset = vmx_adjust_tsc_offset, .set_tdp_cr3 = vmx_set_cr3, + + .prefetch_instruction = vmx_prefetch_instruction, }; static int __init vmx_init(void) -- 1.6.4 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
