Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Mon, 7 Feb 2022 19:21:19 +0000
From:   Sean Christopherson <seanjc@google.com>
To:     Hou Wenlong <houwenlong.hwl@antgroup.com>
Cc:     kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org,
        "H. Peter Anvin" <hpa@zytor.com>,
        Marcelo Tosatti <mtosatti@redhat.com>,
        Gleb Natapov <gleb@redhat.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] KVM: x86/emulator: Defer not-present segment check
 in __load_segment_descriptor()
Message-ID: <YgFxL1uTKPCUpokQ@google.com>
References: <cover.1642669684.git.houwenlong.hwl@antgroup.com>
 <117283244eab58e94d589af58a5f2b245b8c0025.1642669684.git.houwenlong.hwl@antgroup.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <117283244eab58e94d589af58a5f2b245b8c0025.1642669684.git.houwenlong.hwl@antgroup.com>
Precedence: bulk

On Thu, Jan 20, 2022, Hou Wenlong wrote:
> Per Intel's SDM on the "Instruction Set Reference", when
> loading segment descriptor, not-present segment check should
> be after all type and privilege checks. But the emulator checks
> it first, then #NP is triggered instead of #GP if privilege fails
> and segment is not present. Put not-present segment check after
> type and privilege checks in __load_segment_descriptor().

For posterity, KVM doesn't support CALL GATES or TASK GATES, so the "early" #NP
check for those is missing.

> Fixes: 38ba30ba51a00 (KVM: x86 emulator: Emulate task switch in emulator.c)
> Signed-off-by: Hou Wenlong <houwenlong.hwl@antgroup.com>
> ---

Reviewed-by: Sean Christopherson <seanjc@google.com>