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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id c6sm577571ede.17.2021.06.23.13.22.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 23 Jun 2021 13:22:55 -0700 (PDT) Subject: Re: [PATCH 50/54] KVM: x86/mmu: Optimize and clean up so called "last nonleaf level" logic To: Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Yu Zhang , Maxim Levitsky References: <20210622175739.3610207-1-seanjc@google.com> <20210622175739.3610207-51-seanjc@google.com> From: Paolo Bonzini Message-ID: Date: Wed, 23 Jun 2021 22:22:54 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210622175739.3610207-51-seanjc@google.com> 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 22/06/21 19:57, Sean Christopherson wrote: > For 32-bit paging (non-PAE), the adjustments are needed purely because > bit 7 is ignored if PSE=0. Retain that logic as is, but make > is_last_gpte() unique per PTTYPE ... which makes total sense given where it's used, too. > +#if PTTYPE == 32 > + /* > + * 32-bit paging requires special handling because bit 7 is ignored if > + * CR4.PSE=0, not reserved. Clear bit 7 in the gpte if the level is > + * greater than the last level for which bit 7 is the PAGE_SIZE bit. > + * > + * The RHS has bit 7 set iff level < (2 + PSE). If it is clear, bit 7 > + * is not reserved and does not indicate a large page at this level, > + * so clear PT_PAGE_SIZE_MASK in gpte if that is the case. > + */ > + gpte &= level - (PT32_ROOT_LEVEL + !!mmu->mmu_role.ext.cr4_pse); !! is not needed and possibly slightly confusing? (We know it's a single bit). Paolo