1b7fcd3263
The KVM MMU tries to detect when a speculative pte update is not actually used by demand fault, by checking the accessed bit of the shadow pte. If the shadow pte has not been accessed, we deem that page table flooded and remove the shadow page table, allowing further pte updates to proceed without emulation. However, if the pte itself points at a page table and only used for write operations, the accessed bit will never be set since all access will happen through the emulator. This is exactly what happens with kscand on old (2.4.x) HIGHMEM kernels. The kernel points a kmap_atomic() pte at a page table, and then proceeds with read-modify-write operations to look at the dirty and accessed bits. We get a false flood trigger on the kmap ptes, which results in the mmu spending all its time setting up and tearing down shadows. Fix by setting the shadow accessed bit on emulated accesses. Signed-off-by: Avi Kivity <avi@qumranet.com>
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
#ifndef __KVM_X86_MMU_H
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#define __KVM_X86_MMU_H
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#include <linux/kvm_host.h>
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#define PT64_PT_BITS 9
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#define PT64_ENT_PER_PAGE (1 << PT64_PT_BITS)
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#define PT32_PT_BITS 10
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#define PT32_ENT_PER_PAGE (1 << PT32_PT_BITS)
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#define PT_WRITABLE_SHIFT 1
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#define PT_PRESENT_MASK (1ULL << 0)
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#define PT_WRITABLE_MASK (1ULL << PT_WRITABLE_SHIFT)
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#define PT_USER_MASK (1ULL << 2)
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#define PT_PWT_MASK (1ULL << 3)
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#define PT_PCD_MASK (1ULL << 4)
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#define PT_ACCESSED_SHIFT 5
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#define PT_ACCESSED_MASK (1ULL << PT_ACCESSED_SHIFT)
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#define PT_DIRTY_MASK (1ULL << 6)
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#define PT_PAGE_SIZE_MASK (1ULL << 7)
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#define PT_PAT_MASK (1ULL << 7)
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#define PT_GLOBAL_MASK (1ULL << 8)
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#define PT64_NX_SHIFT 63
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#define PT64_NX_MASK (1ULL << PT64_NX_SHIFT)
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#define PT_PAT_SHIFT 7
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#define PT_DIR_PAT_SHIFT 12
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#define PT_DIR_PAT_MASK (1ULL << PT_DIR_PAT_SHIFT)
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#define PT32_DIR_PSE36_SIZE 4
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#define PT32_DIR_PSE36_SHIFT 13
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#define PT32_DIR_PSE36_MASK \
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(((1ULL << PT32_DIR_PSE36_SIZE) - 1) << PT32_DIR_PSE36_SHIFT)
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#define PT64_ROOT_LEVEL 4
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#define PT32_ROOT_LEVEL 2
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#define PT32E_ROOT_LEVEL 3
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static inline void kvm_mmu_free_some_pages(struct kvm_vcpu *vcpu)
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{
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if (unlikely(vcpu->kvm->arch.n_free_mmu_pages < KVM_MIN_FREE_MMU_PAGES))
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__kvm_mmu_free_some_pages(vcpu);
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}
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static inline int kvm_mmu_reload(struct kvm_vcpu *vcpu)
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{
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if (likely(vcpu->arch.mmu.root_hpa != INVALID_PAGE))
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return 0;
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return kvm_mmu_load(vcpu);
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}
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static inline int is_long_mode(struct kvm_vcpu *vcpu)
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{
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#ifdef CONFIG_X86_64
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return vcpu->arch.shadow_efer & EFER_LME;
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#else
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return 0;
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#endif
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}
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static inline int is_pae(struct kvm_vcpu *vcpu)
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{
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return vcpu->arch.cr4 & X86_CR4_PAE;
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}
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static inline int is_pse(struct kvm_vcpu *vcpu)
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{
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return vcpu->arch.cr4 & X86_CR4_PSE;
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}
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static inline int is_paging(struct kvm_vcpu *vcpu)
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{
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return vcpu->arch.cr0 & X86_CR0_PG;
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}
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#endif
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