From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>,
Adrian Hunter <adrian.hunter@intel.com>,
kvm@vger.kernel.org, rick.p.edgecombe@intel.com,
kai.huang@intel.com, reinette.chatre@intel.com,
tony.lindgren@linux.intel.com, binbin.wu@linux.intel.com,
dmatlack@google.com, isaku.yamahata@intel.com,
nik.borisov@suse.com, linux-kernel@vger.kernel.org,
yan.y.zhao@intel.com, chao.gao@intel.com,
weijiang.yang@intel.com
Subject: Re: [PATCH V2 02/12] KVM: x86: Allow the use of kvm_load_host_xsave_state() with guest_state_protected
Date: Thu, 6 Mar 2025 12:43:49 -0800 [thread overview]
Message-ID: <Z8oImITJahUiZbwj@google.com> (raw)
In-Reply-To: <0745c6ee-9d8b-4936-ab1f-cfecceb86735@redhat.com>
On Thu, Mar 06, 2025, Paolo Bonzini wrote:
> I agree with Xiaoyao that this change is sensible but should be proposed
> separately for both SNP and TDX.
>
> Allowing the use of kvm_load_host_xsave_state() is really ugly, especially
> since the corresponding code is so simple:
>
> if (cpu_feature_enabled(X86_FEATURE_PKU) && vcpu->arch.pkru != 0)
> wrpkru(vcpu->arch.host_pkru);
It's clearly not "so simple", because this code is buggy.
The justification for using kvm_load_host_xsave_state() is that either KVM gets
the TDX state model correct and the existing flows Just Work, or we handle all
that state as one-offs and at best replicate concepts and flows, and at worst
have bugs that are unique to TDX, e.g. because we get the "simple" code wrong,
we miss flows that subtly consume state, etc.
next prev parent reply other threads:[~2025-03-06 20:43 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-29 9:58 [PATCH V2 00/12] KVM: TDX: TD vcpu enter/exit Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 01/12] x86/virt/tdx: Make tdh_vp_enter() noinstr Adrian Hunter
2025-02-16 18:26 ` Paolo Bonzini
2025-02-27 14:13 ` Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 02/12] KVM: x86: Allow the use of kvm_load_host_xsave_state() with guest_state_protected Adrian Hunter
2025-02-20 10:50 ` Xiaoyao Li
2025-02-24 11:38 ` Adrian Hunter
2025-02-25 5:56 ` Xiaoyao Li
2025-02-27 14:14 ` Adrian Hunter
2025-03-06 18:04 ` Paolo Bonzini
2025-03-06 20:43 ` Sean Christopherson [this message]
2025-03-06 22:34 ` Paolo Bonzini
2025-03-07 23:04 ` Sean Christopherson
2025-03-10 19:08 ` Paolo Bonzini
2025-01-29 9:58 ` [PATCH V2 03/12] KVM: TDX: Set arch.has_protected_state to true Adrian Hunter
2025-02-20 12:35 ` Xiaoyao Li
2025-02-27 14:17 ` Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 04/12] KVM: VMX: Move common fields of struct vcpu_{vmx,tdx} to a struct Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 05/12] KVM: TDX: Implement TDX vcpu enter/exit path Adrian Hunter
2025-02-20 13:16 ` Xiaoyao Li
2025-02-24 12:27 ` Adrian Hunter
2025-02-25 6:15 ` Xiaoyao Li
2025-02-27 18:37 ` Adrian Hunter
2025-03-06 18:19 ` Paolo Bonzini
2025-03-06 19:13 ` Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 06/12] KVM: TDX: vcpu_run: save/restore host state(host kernel gs) Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 07/12] KVM: TDX: restore host xsave state when exit from the guest TD Adrian Hunter
2025-02-25 6:43 ` Xiaoyao Li
2025-02-27 14:29 ` Adrian Hunter
2025-02-28 1:58 ` Xiaoyao Li
2025-01-29 9:58 ` [PATCH V2 08/12] KVM: x86: Allow to update cached values in kvm_user_return_msrs w/o wrmsr Adrian Hunter
2025-02-25 7:00 ` Xiaoyao Li
2025-01-29 9:58 ` [PATCH V2 09/12] KVM: TDX: restore user ret MSRs Adrian Hunter
2025-02-25 7:01 ` Xiaoyao Li
2025-02-27 14:19 ` Adrian Hunter
2025-01-29 9:58 ` [PATCH V2 10/12] KVM: TDX: Disable support for TSX and WAITPKG Adrian Hunter
2025-01-29 9:59 ` [PATCH V2 11/12] KVM: TDX: Save and restore IA32_DEBUGCTL Adrian Hunter
2025-01-29 9:59 ` [PATCH V2 12/12] KVM: x86: Add a switch_db_regs flag to handle TDX's auto-switched behavior Adrian Hunter
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