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Wed, 28 Oct 2026 17:58:47 +0000 (UTC) Received: from [100.90.222.41] (headnet04.pony-001.prod.iad2.dc.redhat.com [10.2.32.116]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id AD5BE1800495; Wed, 28 Oct 2026 17:58:45 +0000 (UTC) Message-ID: <69437bf0-45fc-4701-9144-a208c12423e6@redhat.com> Date: Wed, 28 Oct 2026 18:58:44 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [REGRESSION] KVM: x86: OVMF boot hang with SMM enabled after commit b3e6212dea2e ("KVM: x86: Use active memslots for the per-vCPU MMIO cache") From: Paolo Bonzini To: Sean Christopherson , Sami Farin , linux-kernel@vger.kernel.org, Greg Kroah-Hartman , kvm@vger.kernel.org, kimjw04271234@gmail.com, stable@vger.kernel.org References: <2026102314-CVE-2026-99082-e5b1@gregkh> <20261027124140.upuow4a3kv6kssvn@m.mifar.in> Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 On 10/28/26 18:48, Paolo Bonzini wrote: > On 10/28/26 18:37, Sean Christopherson wrote: >>> However, address space 0 and address space 1 maintain separate > generation counters >>> starting from 0. > > This is also incorrect: > >         for (i = 0; i < kvm_arch_nr_memslot_as_ids(kvm); i++) { >                 for (j = 0; j < 2; j++) { >                         slots = &kvm->__memslots[i][j]; > >                         atomic_long_set(&slots->last_used_slot, > (unsigned long)NULL); >                         slots->hva_tree = RB_ROOT_CACHED; >                         slots->gfn_tree = RB_ROOT; >                         hash_init(slots->id_hash); >                         slots->node_idx = j; > >                         /* Generations must be different for each > address space. */ >                         slots->generation = i; >                 } > > >>>          An MMIO access cached in SMM (e.g., GFN 0xFED40000 with gen >>> = 4) matches in normal mode where gen is also 4. >> Hmm, this isn't adding up for me.  It should be impossible for the >> generation to >> be '4' for SMM, because SMM is supposed to use odd-numbered >> generations.  From >> kvm_swap_active_memslots(): > > vcpu_cache_mmio_info() does not use the address space id: > >         u64 gen = kvm_memslots(vcpu->kvm)->generation; > > Will send a patch soon. Nevermind, wrong tree - I was reinventing the (apparently buggy) commit because it's past 7.3.0-rc7... still looking. Paolo