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([2001:b07:6468:f312:9fd9:16f2:2095:52d7]) by smtp.gmail.com with ESMTPSA id d6sm11141635wrq.67.2020.09.12.09.32.38 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 12 Sep 2020 09:32:38 -0700 (PDT) Subject: Re: [PATCH v3 8/8] KVM: nSVM: implement ondemand allocation of the nested state To: Maxim Levitsky , kvm@vger.kernel.org Cc: Sean Christopherson , "open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Borislav Petkov , "H. Peter Anvin" , Vitaly Kuznetsov , "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" , Jim Mattson , Thomas Gleixner , Ingo Molnar , Joerg Roedel , Wanpeng Li References: <20200827171145.374620-1-mlevitsk@redhat.com> <20200827171145.374620-9-mlevitsk@redhat.com> From: Paolo Bonzini Message-ID: <58f9d2c1-0739-5b72-ee21-285474666c58@redhat.com> Date: Sat, 12 Sep 2020 18:32:37 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200827171145.374620-9-mlevitsk@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 27/08/20 19:11, Maxim Levitsky wrote: > + hsave_page = alloc_page(GFP_KERNEL_ACCOUNT | __GFP_ZERO); > + if (!hsave_page) > + goto error; > + I think an error here should be just an internal error userspace exit, or a -ENOMEM from KVM_RUN; not a #GP in the guest[1]. However, that's difficult to plug into KVM. Can you instead allocate nested state if KVM_SET_CPUID2 sets the SVM bit? Returning -ENOMEM from KVM_SET_CPUID2 is more likely to be something that userspace copes with. I queued patches 1-5, and 7 for 5.9-rc. Paolo [1] Though in practice an order 0 allocation will never fail