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Message-ID: <2f22aeeb-7109-4d3f-bcb7-58ef7f8e0d4c@intel.com>
Date: Fri, 22 Nov 2024 13:23:54 +0800
From: Xiaoyao Li <xiaoyao.li@...el.com>
To: Adrian Hunter <adrian.hunter@...el.com>, pbonzini@...hat.com,
seanjc@...gle.com, kvm@...r.kernel.org, dave.hansen@...ux.intel.com
Cc: rick.p.edgecombe@...el.com, kai.huang@...el.com,
reinette.chatre@...el.com, tony.lindgren@...ux.intel.com,
binbin.wu@...ux.intel.com, dmatlack@...gle.com, isaku.yamahata@...el.com,
nik.borisov@...e.com, linux-kernel@...r.kernel.org, x86@...nel.org,
yan.y.zhao@...el.com, chao.gao@...el.com, weijiang.yang@...el.com
Subject: Re: [PATCH 2/7] KVM: TDX: Implement TDX vcpu enter/exit path
On 11/22/2024 4:14 AM, Adrian Hunter wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> This patch implements running TDX vcpu. Once vcpu runs on the logical
> processor (LP), the TDX vcpu is associated with it. When the TDX vcpu
> moves to another LP, the TDX vcpu needs to flush its status on the LP.
> When destroying TDX vcpu, it needs to complete flush, and flush cpu memory
> cache. Track which LP the TDX vcpu run and flush it as necessary.
The changelog needs update. It doesn't match the patch content.
> Compared to VMX, do nothing on sched_in event as TDX doesn't support pause
> loop.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
> ---
> TD vcpu enter/exit v1:
> - Make argument of tdx_vcpu_enter_exit() struct kvm_vcpu.
> - Update for the wrapper functions for SEAMCALLs. (Sean)
> - Remove noinstr (Sean)
> - Add a missing comma, clarify sched_in part, and update changelog to
> match code by dropping the PMU related paragraph (Binbin)
> https://lore.kernel.org/lkml/c0029d4d-3dee-4f11-a929-d64d2651bfb3@linux.intel.com/
> - Remove the union tdx_exit_reason. (Sean)
> https://lore.kernel.org/kvm/ZfSExlemFMKjBtZb@google.com/
> - Remove the code of special handling of vcpu->kvm->vm_bugged (Rick)
> https://lore.kernel.org/kvm/20240318234010.GD1645738@ls.amr.corp.intel.com/
> - For !tdx->initialized case, set tdx->vp_enter_ret to TDX_SW_ERROR to avoid
> collision with EXIT_REASON_EXCEPTION_NMI.
>
> v19:
> - Removed export_symbol_gpl(host_xcr0) to the patch that uses it
>
> Changes v15 -> v16:
> - use __seamcall_saved_ret()
> - As struct tdx_module_args doesn't match with vcpu.arch.regs, copy regs
> before/after calling __seamcall_saved_ret().
> ---
> arch/x86/kvm/vmx/main.c | 21 ++++++++++-
> arch/x86/kvm/vmx/tdx.c | 76 ++++++++++++++++++++++++++++++++++++++
> arch/x86/kvm/vmx/tdx.h | 2 +
> arch/x86/kvm/vmx/x86_ops.h | 5 +++
> 4 files changed, 102 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index bfed421e6fbb..44ec6005a448 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -129,6 +129,23 @@ static void vt_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
> vmx_vcpu_load(vcpu, cpu);
> }
>
> +static int vt_vcpu_pre_run(struct kvm_vcpu *vcpu)
> +{
> + if (is_td_vcpu(vcpu))
> + /* Unconditionally continue to vcpu_run(). */
> + return 1;
> +
> + return vmx_vcpu_pre_run(vcpu);
> +}
> +
> +static fastpath_t vt_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
> +{
> + if (is_td_vcpu(vcpu))
> + return tdx_vcpu_run(vcpu, force_immediate_exit);
> +
> + return vmx_vcpu_run(vcpu, force_immediate_exit);
> +}
> +
> static void vt_flush_tlb_all(struct kvm_vcpu *vcpu)
> {
> if (is_td_vcpu(vcpu)) {
> @@ -267,8 +284,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
> .flush_tlb_gva = vt_flush_tlb_gva,
> .flush_tlb_guest = vt_flush_tlb_guest,
>
> - .vcpu_pre_run = vmx_vcpu_pre_run,
> - .vcpu_run = vmx_vcpu_run,
> + .vcpu_pre_run = vt_vcpu_pre_run,
> + .vcpu_run = vt_vcpu_run,
> .handle_exit = vmx_handle_exit,
> .skip_emulated_instruction = vmx_skip_emulated_instruction,
> .update_emulated_instruction = vmx_update_emulated_instruction,
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index dc6c5f40608e..5fa5b65b9588 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -10,6 +10,9 @@
> #include "mmu/spte.h"
> #include "common.h"
>
> +#include <trace/events/kvm.h>
> +#include "trace.h"
> +
> #undef pr_fmt
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> @@ -662,6 +665,79 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu)
> }
>
>
> +static void tdx_vcpu_enter_exit(struct kvm_vcpu *vcpu)
> +{
> + struct vcpu_tdx *tdx = to_tdx(vcpu);
> + struct tdx_module_args args;
> +
> + guest_state_enter_irqoff();
> +
> + /*
> + * TODO: optimization:
> + * - Eliminate copy between args and vcpu->arch.regs.
> + * - copyin/copyout registers only if (tdx->tdvmvall.regs_mask != 0)
> + * which means TDG.VP.VMCALL.
> + */
> + args = (struct tdx_module_args) {
> + .rcx = tdx->tdvpr_pa,
> +#define REG(reg, REG) .reg = vcpu->arch.regs[VCPU_REGS_ ## REG]
> + REG(rdx, RDX),
> + REG(r8, R8),
> + REG(r9, R9),
> + REG(r10, R10),
> + REG(r11, R11),
> + REG(r12, R12),
> + REG(r13, R13),
> + REG(r14, R14),
> + REG(r15, R15),
> + REG(rbx, RBX),
> + REG(rdi, RDI),
> + REG(rsi, RSI),
> +#undef REG
> + };
> +
> + tdx->vp_enter_ret = tdh_vp_enter(tdx->tdvpr_pa, &args);
> +
> +#define REG(reg, REG) vcpu->arch.regs[VCPU_REGS_ ## REG] = args.reg
> + REG(rcx, RCX);
> + REG(rdx, RDX);
> + REG(r8, R8);
> + REG(r9, R9);
> + REG(r10, R10);
> + REG(r11, R11);
> + REG(r12, R12);
> + REG(r13, R13);
> + REG(r14, R14);
> + REG(r15, R15);
> + REG(rbx, RBX);
> + REG(rdi, RDI);
> + REG(rsi, RSI);
> +#undef REG
> +
> + guest_state_exit_irqoff();
> +}
> +
> +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
> +{
> + struct vcpu_tdx *tdx = to_tdx(vcpu);
> +
> + /* TDX exit handle takes care of this error case. */
> + if (unlikely(tdx->state != VCPU_TD_STATE_INITIALIZED)) {
> + /* Set to avoid collision with EXIT_REASON_EXCEPTION_NMI. */
It seems the check fits better in tdx_vcpu_pre_run().
And without the patch of how TDX handles Exit (i.e., how deal with
vp_enter_ret), it's hard to review this comment.
> + tdx->vp_enter_ret = TDX_SW_ERROR;
> + return EXIT_FASTPATH_NONE;
> + }
> +
> + trace_kvm_entry(vcpu, force_immediate_exit);
> +
> + tdx_vcpu_enter_exit(vcpu);
> +
> + vcpu->arch.regs_avail &= ~VMX_REGS_LAZY_LOAD_SET;
> + trace_kvm_exit(vcpu, KVM_ISA_VMX);
> +
> + return EXIT_FASTPATH_NONE;
> +}
> +
> void tdx_load_mmu_pgd(struct kvm_vcpu *vcpu, hpa_t root_hpa, int pgd_level)
> {
> u64 shared_bit = (pgd_level == 5) ? TDX_SHARED_BIT_PWL_5 :
> diff --git a/arch/x86/kvm/vmx/tdx.h b/arch/x86/kvm/vmx/tdx.h
> index 899654519df6..ebee1049b08b 100644
> --- a/arch/x86/kvm/vmx/tdx.h
> +++ b/arch/x86/kvm/vmx/tdx.h
> @@ -51,6 +51,8 @@ struct vcpu_tdx {
>
> struct list_head cpu_list;
>
> + u64 vp_enter_ret;
> +
> enum vcpu_tdx_state state;
> };
>
> diff --git a/arch/x86/kvm/vmx/x86_ops.h b/arch/x86/kvm/vmx/x86_ops.h
> index 06583b1afa4f..3d292a677b92 100644
> --- a/arch/x86/kvm/vmx/x86_ops.h
> +++ b/arch/x86/kvm/vmx/x86_ops.h
> @@ -129,6 +129,7 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp);
> int tdx_vcpu_create(struct kvm_vcpu *vcpu);
> void tdx_vcpu_free(struct kvm_vcpu *vcpu);
> void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu);
> +fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit);
>
> int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp);
>
> @@ -156,6 +157,10 @@ static inline int tdx_vm_ioctl(struct kvm *kvm, void __user *argp) { return -EOP
> static inline int tdx_vcpu_create(struct kvm_vcpu *vcpu) { return -EOPNOTSUPP; }
> static inline void tdx_vcpu_free(struct kvm_vcpu *vcpu) {}
> static inline void tdx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) {}
> +static inline fastpath_t tdx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit)
> +{
> + return EXIT_FASTPATH_NONE;
> +}
>
> static inline int tdx_vcpu_ioctl(struct kvm_vcpu *vcpu, void __user *argp) { return -EOPNOTSUPP; }
>
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