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SubjectRe: [PATCH v3 2/5] KVM: X86: Introduce need_cancel_enter_guest helper
On Fri, Apr 24, 2020 at 02:22:41PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@tencent.com>
>
> Introduce need_cancel_enter_guest() helper, we need to check some
> conditions before doing CONT_RUN, in addition, it can also catch
> the case vmexit occurred while another event was being delivered
> to guest software since vmx_complete_interrupts() adds the request
> bit.
>
> Tested-by: Haiwei Li <lihaiwei@tencent.com>
> Cc: Haiwei Li <lihaiwei@tencent.com>
> Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
> ---
> arch/x86/kvm/vmx/vmx.c | 12 +++++++-----
> arch/x86/kvm/x86.c | 10 ++++++++--
> arch/x86/kvm/x86.h | 1 +
> 3 files changed, 16 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index f1f6638..5c21027 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6577,7 +6577,7 @@ bool __vmx_vcpu_run(struct vcpu_vmx *vmx, unsigned long *regs, bool launched);
>
> static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
> {
> - enum exit_fastpath_completion exit_fastpath;
> + enum exit_fastpath_completion exit_fastpath = EXIT_FASTPATH_NONE;
> struct vcpu_vmx *vmx = to_vmx(vcpu);
> unsigned long cr3, cr4;
>
> @@ -6754,10 +6754,12 @@ static enum exit_fastpath_completion vmx_vcpu_run(struct kvm_vcpu *vcpu)
> vmx_recover_nmi_blocking(vmx);
> vmx_complete_interrupts(vmx);
>
> - exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
> - /* static call is better with retpolines */
> - if (exit_fastpath == EXIT_FASTPATH_CONT_RUN)
> - goto cont_run;
> + if (!kvm_need_cancel_enter_guest(vcpu)) {
> + exit_fastpath = vmx_exit_handlers_fastpath(vcpu);
> + /* static call is better with retpolines */
> + if (exit_fastpath == EXIT_FASTPATH_CONT_RUN)
> + goto cont_run;
> + }
>
> return exit_fastpath;
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 59958ce..4561104 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -1581,6 +1581,13 @@ int kvm_emulate_wrmsr(struct kvm_vcpu *vcpu)
> }
> EXPORT_SYMBOL_GPL(kvm_emulate_wrmsr);
>
> +bool kvm_need_cancel_enter_guest(struct kvm_vcpu *vcpu)

What about kvm_vcpu_<???>_pending()? Not sure what a good ??? would be.
The "cancel_enter_guest" wording is a bit confusing when this is called
from the VM-Exit path.

> +{
> + return (vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu)
> + || need_resched() || signal_pending(current));

Parantheses around the whole statement are unnecessary. Personal preference
is to put the || before the newline.

> +}
> +EXPORT_SYMBOL_GPL(kvm_need_cancel_enter_guest);
> +
> /*
> * The fast path for frequent and performance sensitive wrmsr emulation,
> * i.e. the sending of IPI, sending IPI early in the VM-Exit flow reduces
> @@ -8373,8 +8380,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
> if (kvm_lapic_enabled(vcpu) && vcpu->arch.apicv_active)
> kvm_x86_ops.sync_pir_to_irr(vcpu);
>
> - if (vcpu->mode == EXITING_GUEST_MODE || kvm_request_pending(vcpu)
> - || need_resched() || signal_pending(current)) {
> + if (kvm_need_cancel_enter_guest(vcpu)) {
> vcpu->mode = OUTSIDE_GUEST_MODE;
> smp_wmb();
> local_irq_enable();
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index 7b5ed8e..1906e7e 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -364,5 +364,6 @@ static inline bool kvm_dr7_valid(u64 data)
> void kvm_load_guest_xsave_state(struct kvm_vcpu *vcpu);
> void kvm_load_host_xsave_state(struct kvm_vcpu *vcpu);
> u64 kvm_spec_ctrl_valid_bits(struct kvm_vcpu *vcpu);
> +bool kvm_need_cancel_enter_guest(struct kvm_vcpu *vcpu);
>
> #endif
> --
> 2.7.4
>

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