On Tue, May 07, 2024 at 03:06:57PM +0800, Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx> wrote: > > > > + /* > > > > + * The only reason it gets EXIT_REASON_OTHER_SMI is there is an > > > > + * #MSMI(Machine Check System Management Interrupt) with > > > > + * exit_qualification bit 0 set in TD guest. > > > > + * The #MSMI is delivered right after SEAMCALL returns, > > > > + * and an #MC is delivered to host kernel after SMI handler > > > > + * returns. > > > > + * > > > > + * The #MC right after SEAMCALL is fixed up and skipped in #MC > > > Looks fixing up and skipping #MC on the first instruction after TD-exit is > > > missing in v19? > > Right. We removed it as MSMI will provides if #MC happened in SEAM or not. > > According to the patch of host #MC handler > https://lore.kernel.org/lkml/171265126376.10875.16864387954272613660.tip-bot2@tip-bot2/, > the #MC triggered by MSMI can be handled by kernel #MC handler. > There is no need to call kvm_machine_check(). > > Does the following fixup make sense to you? Yes. Now this patch becomes mostly none. So it makes more sense to squash this patch into [PATCH v19 100/130] KVM: TDX: handle EXIT_REASON_OTHER_SMI. > -------- > > KVM: TDX: Handle EXIT_REASON_OTHER_SMI > > Handle "Other SMI" VM exit for TDX. > > Unlike VMX, an SMI occurs in SEAM non-root mode cause VM exit to TDX > module, then SEAMRET to KVM. Once it exits to KVM, SMI is delivered and > handled by kernel handler right away. > > Specifically, when BIOS eMCA MCE-SMI morphing is enabled, the #MC occurs > in TDX guest is delivered as an Machine Check System Management Interrupt > (MSMI) with the exit reason of EXIT_REASON_OTHER_SMI with MSMI (bit 0) set > in the exit qualification. On VM exit, TDX module checks whether the "Other > SMI" is caused by a MSMI or not. If so, TDX module makes TD as fatal, > preventing further TD entries, and then completes the TD exit flow to KVM > with the TDH.VP.ENTER outputs indicating TDX_NON_RECOVERABLE_TD. > After TD exit, the MSMI is delivered and eventually handled by the kernel > #MC handler[1]. > > So, to handle "Other SMI" VM exit: > - For non-MSMI case, KVM doesn't need to do anything, just continue TDX vCPU > execution. > - For MSMI case, since the TDX guest is dead, follow other non-recoverable > cases, exit to userspace. > > [1] The patch supports handling MSMI signaled during SEAM operation. > It's already in tip tree. > https://lore.kernel.org/lkml/171265126376.10875.16864387954272613660.tip-bot2@tip-bot2/ > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index 4ee94bfb17e2..fd756d231204 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -975,30 +975,6 @@ void tdx_handle_exit_irqoff(struct kvm_vcpu *vcpu) > tdexit_intr_info(vcpu)); > else if (exit_reason == EXIT_REASON_EXCEPTION_NMI) > vmx_handle_exception_irqoff(vcpu, tdexit_intr_info(vcpu)); > - else if (unlikely(tdx->exit_reason.non_recoverable || > - tdx->exit_reason.error)) { > - /* > - * The only reason it gets EXIT_REASON_OTHER_SMI is there is > an > - * #MSMI(Machine Check System Management Interrupt) with > - * exit_qualification bit 0 set in TD guest. > - * The #MSMI is delivered right after SEAMCALL returns, > - * and an #MC is delivered to host kernel after SMI handler > - * returns. > - * > - * The #MC right after SEAMCALL is fixed up and skipped in > #MC > - * handler because it's an #MC happens in TD guest we cannot > - * handle it with host's context. > - * > - * Call KVM's machine check handler explicitly here. > - */ > - if (tdx->exit_reason.basic == EXIT_REASON_OTHER_SMI) { > - unsigned long exit_qual; > - > - exit_qual = tdexit_exit_qual(vcpu); > - if (exit_qual & TD_EXIT_OTHER_SMI_IS_MSMI) > - kvm_machine_check(); > - } > - } > } > > static int tdx_handle_exception(struct kvm_vcpu *vcpu) > @@ -1923,10 +1899,6 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t > fastpath) > to_kvm_tdx(vcpu->kvm)->hkid, > set_hkid_to_hpa(0, > to_kvm_tdx(vcpu->kvm)->hkid)); > > - /* > - * tdx_handle_exit_irqoff() handled EXIT_REASON_OTHER_SMI. > It > - * must be handled before enabling preemption because it's > #MC. > - */ > goto unhandled_exit; > } > > @@ -1970,14 +1942,14 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, > fastpath_t fastpath) > return tdx_handle_ept_misconfig(vcpu); > case EXIT_REASON_OTHER_SMI: > /* > - * Unlike VMX, all the SMI in SEAM non-root mode (i.e. when > - * TD guest vcpu is running) will cause TD exit to TDX > module, > - * then SEAMRET to KVM. Once it exits to KVM, SMI is > delivered > - * and handled right away. > + * Unlike VMX, SMI occurs in SEAM non-root mode (i.e. when > + * TD guest vCPU is running) will cause VM exit to TDX > module, > + * then SEAMRET to KVM. Once it exits to KVM, SMI is > delivered > + * and handled by kernel handler right away. > * > - * - If it's an Machine Check System Management Interrupt > - * (MSMI), it's handled above due to non_recoverable bit > set. > - * - If it's not an MSMI, don't need to do anything here. > + * - A MSMI will not reach here, it's handled as > non_recoverable > + * case above. > + * - If it's not a MSMI, no need to do anything here. > */ > return 1; > default: > diff --git a/arch/x86/kvm/vmx/tdx_arch.h b/arch/x86/kvm/vmx/tdx_arch.h > index 2aecffe9f276..aa2fea7b2652 100644 > --- a/arch/x86/kvm/vmx/tdx_arch.h > +++ b/arch/x86/kvm/vmx/tdx_arch.h > @@ -41,8 +41,6 @@ > #define TDH_PHYMEM_PAGE_WBINVD 41 > #define TDH_VP_WR 43 > > -#define TD_EXIT_OTHER_SMI_IS_MSMI BIT_ULL(1) > - > /* TDX control structure (TDR/TDCS/TDVPS) field access codes */ > #define TDX_NON_ARCH BIT_ULL(63) > #define TDX_CLASS_SHIFT 56 > > > -- Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
