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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=J3dDjttD8k2nIqq+9CGJb1KBqxep2rp0RSh3PBJu3l7FP+d840idhtvhdmD2DMo8r UF7JkpU24jM06uX2+P1cZ0CaNAjXgVjtWVgKuwaqeDlIgRi7+HKdAbkdcRUG7djMwY XzeNQNqHJFck+wIXG4LiY70Is2NOlTvrt1XjmUvaFKR4uKqJNERE+HiQ6v5zui6hdz XITc+TnZsZEPNfR0AG/CBD9XGMDGO6/HOaD0/PkVeNOzRVbotnSPKrWqQVKvw++MiM 3BOS21m9y2QqbTgeCgKLEv7wcL9T+J2b9RgCLO1McwGwHVru4MbVyYs+AuZ2bBB+5s 4kGGcEeKN8ApQ== Message-ID: <7f33ee53-1569-4a47-8018-fd48e9c65901@zytor.com> Date: Tue, 14 Oct 2025 15:49:59 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 18/21] KVM: nVMX: Add FRED VMCS fields to nested VMX context handling To: Chao Gao Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, pbonzini@redhat.com, seanjc@google.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, hch@infradead.org References: <20251014010950.1568389-1-xin@zytor.com> <20251014010950.1568389-19-xin@zytor.com> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/14/2025 2:57 PM, Chao Gao wrote: >> + if (!vmx->nested.nested_run_pending || >> + !nested_cpu_load_guest_fred_state(vmcs12)) { >> + vmx->nested.pre_vmenter_fred_config = vmcs_read64(GUEST_IA32_FRED_CONFIG); >> + vmx->nested.pre_vmenter_fred_rsp1 = vmcs_read64(GUEST_IA32_FRED_RSP1); >> + vmx->nested.pre_vmenter_fred_rsp2 = vmcs_read64(GUEST_IA32_FRED_RSP2); >> + vmx->nested.pre_vmenter_fred_rsp3 = vmcs_read64(GUEST_IA32_FRED_RSP3); >> + vmx->nested.pre_vmenter_fred_stklvls = vmcs_read64(GUEST_IA32_FRED_STKLVLS); >> + vmx->nested.pre_vmenter_fred_ssp1 = vmcs_read64(GUEST_IA32_FRED_SSP1); >> + vmx->nested.pre_vmenter_fred_ssp2 = vmcs_read64(GUEST_IA32_FRED_SSP2); >> + vmx->nested.pre_vmenter_fred_ssp3 = vmcs_read64(GUEST_IA32_FRED_SSP3); > FRED state save/restore is needed only when the guest has FRED support. So, the > above save/restore should be guarded by guest_cpu_cap_has(vcpu, X86_FEATURE_FRED). > Otherwise, on hardware without FRED, vmread_error() would be triggered here as > reported by syzbot. You're right, I wanted to avoid unnecessary checking, but this caught me. Will fix it with a v8A patch.