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([2001:b07:add:ec09:c399:bc87:7b6c:fb2a]) by smtp.gmail.com with ESMTPSA id h16sm2114466wre.52.2021.08.04.03.53.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Aug 2021 03:53:14 -0700 (PDT) Subject: Re: [PATCH v2] KVM: SVM: improve the code readability for ASID management To: Sean Christopherson , Mingwei Zhang Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Tom Lendacky , Marc Orr , David Rientjes , Alper Gun , Dionna Glaze , Vipin Sharma , Peter Gonda , Brijesh Singh References: <20210802180903.159381-1-mizhang@google.com> From: Paolo Bonzini Message-ID: <3226fb50-94c3-49d2-de9a-d4fea81b5b0a@redhat.com> Date: Wed, 4 Aug 2021 12:53:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03/08/21 18:50, Sean Christopherson wrote: > This patch missed sev_asid_free(). > > And on a very related topic, I'm pretty sure the VMCB+ASID invalidation logic > indexes sev_vmcbs incorrectly. pre_sev_run() indexes sev_vmcbs by the ASID, > whereas sev_asid_free() indexes by ASID-1, i.e. on free KVM nullifies the wrong > sev_vmcb entry. sev_cpu_init() allocates for max_sev_asid+1, so indexing by > ASID appears to be the intended behavior. That code is also a good candidate for > conversion to nr_asids in this patch. It's also missing this (off by one for SEV guests, pointless extra work for SEV-ES): index da5b9515a47b..7fbce342eec4 100644 --- a/arch/x86/kvm/svm/sev.c +++ b/arch/x86/kvm/svm/sev.c @@ -147,7 +147,7 @@ static int sev_asid_new(struct kvm_sev_info *sev) min_asid = sev->es_active ? 1 : min_sev_asid; max_asid = sev->es_active ? min_sev_asid - 1 : max_sev_asid; again: - asid = find_next_zero_bit(sev_asid_bitmap, max_sev_asid, min_asid); + asid = find_next_zero_bit(sev_asid_bitmap, max_asid + 1, min_asid); if (asid > max_asid) { if (retry && __sev_recycle_asids(min_asid, max_asid)) { retry = false; Queued both Mingwei's patch and yours, thanks (to 5.14-rc in order to avoid conflicts). Paolo