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Fri, 26 Jun 2026 10:46:32 -0700 (PDT) X-Received: by 2002:a05:600c:a086:b0:492:6954:1036 with SMTP id 5b1f17b1804b1-49269541111mr72347355e9.14.1782495992589; Fri, 26 Jun 2026 10:46:32 -0700 (PDT) Received: from [192.168.10.48] ([151.95.124.208]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46c221d998esm25805016f8f.24.2026.06.26.10.46.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 26 Jun 2026 10:46:32 -0700 (PDT) From: Paolo Bonzini To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, stable@vger.kernel.org Cc: David Matlack Subject: [PATCH 5.15.y v2 4/8] KVM: x86/mmu: Always pass 0 for @quadrant when gptes are 8 bytes Date: Fri, 26 Jun 2026 19:46:15 +0200 Message-ID: <20260626174620.1819772-5-pbonzini@redhat.com> X-Mailer: git-send-email 2.54.0 In-Reply-To: <20260626174620.1819772-1-pbonzini@redhat.com> References: <20260626174620.1819772-1-pbonzini@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit commit 7f49777550e55a7d6832cbb0873f48f91c175b9c upstream. The quadrant is only used when gptes are 4 bytes, but mmu_alloc_{direct,shadow}_roots() pass in a non-zero quadrant for PAE page directories regardless. Make this less confusing by only passing in a non-zero quadrant when it is actually necessary. Signed-off-by: David Matlack Message-Id: <20220516232138.1783324-6-dmatlack@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu/mmu.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c index 3a5ed9670377..dbc18d4cc572 100644 --- a/arch/x86/kvm/mmu/mmu.c +++ b/arch/x86/kvm/mmu/mmu.c @@ -3444,9 +3444,10 @@ static hpa_t mmu_alloc_root(struct kvm_vcpu *vcpu, gfn_t gfn, int quadrant, struct kvm_mmu_page *sp; role.level = level; + role.quadrant = quadrant; - if (!role.gpte_is_8_bytes) - role.quadrant = quadrant; + WARN_ON_ONCE(quadrant && role.gpte_is_8_bytes); + WARN_ON_ONCE(role.direct && !role.gpte_is_8_bytes); sp = kvm_mmu_get_page(vcpu, gfn, role); ++sp->root_count; @@ -3482,7 +3483,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) for (i = 0; i < 4; ++i) { WARN_ON_ONCE(IS_VALID_PAE_ROOT(mmu->pae_root[i])); - root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), i, + root = mmu_alloc_root(vcpu, i << (30 - PAGE_SHIFT), 0, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | PT_PRESENT_MASK | shadow_me_mask; @@ -3506,9 +3507,8 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) struct kvm_mmu *mmu = vcpu->arch.mmu; u64 pdptrs[4], pm_mask; gfn_t root_gfn, root_pgd; + int quadrant, i, r; hpa_t root; - unsigned i; - int r; root_pgd = mmu->get_guest_pgd(vcpu); root_gfn = root_pgd >> PAGE_SHIFT; @@ -3591,7 +3591,15 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) root_gfn = pdptrs[i] >> PAGE_SHIFT; } - root = mmu_alloc_root(vcpu, root_gfn, i, PT32_ROOT_LEVEL); + /* + * If shadowing 32-bit non-PAE page tables, each PAE page + * directory maps one quarter of the guest's non-PAE page + * directory. Othwerise each PAE page direct shadows one guest + * PAE page directory so that quadrant should be 0. + */ + quadrant = !mmu->mmu_role.base.gpte_is_8_bytes ? i : 0; + + root = mmu_alloc_root(vcpu, root_gfn, quadrant, PT32_ROOT_LEVEL); mmu->pae_root[i] = root | pm_mask; } -- 2.54.0