From 006100212d7f1d608a97af37bf218d87afb80db6 Mon Sep 17 00:00:00 2001 From: David Matlack Date: Tue, 25 Jan 2022 23:05:16 +0000 Subject: KVM: x86/mmu: Move is_writable_pte() to spte.h Move is_writable_pte() close to the other functions that check writability information about SPTEs. While here opportunistically replace the open-coded bit arithmetic in check_spte_writable_invariants() with a call to is_writable_pte(). No functional change intended. Suggested-by: Sean Christopherson Signed-off-by: David Matlack Message-Id: <20220125230518.1697048-4-dmatlack@google.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/mmu.h | 38 -------------------------------------- 1 file changed, 38 deletions(-) (limited to 'arch/x86/kvm/mmu.h') diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h index e9fbb2c8bbe2..51faa2c76ca5 100644 --- a/arch/x86/kvm/mmu.h +++ b/arch/x86/kvm/mmu.h @@ -202,44 +202,6 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, return vcpu->arch.mmu->page_fault(vcpu, &fault); } -/* - * Currently, we have two sorts of write-protection, a) the first one - * write-protects guest page to sync the guest modification, b) another one is - * used to sync dirty bitmap when we do KVM_GET_DIRTY_LOG. The differences - * between these two sorts are: - * 1) the first case clears MMU-writable bit. - * 2) the first case requires flushing tlb immediately avoiding corrupting - * shadow page table between all vcpus so it should be in the protection of - * mmu-lock. And the another case does not need to flush tlb until returning - * the dirty bitmap to userspace since it only write-protects the page - * logged in the bitmap, that means the page in the dirty bitmap is not - * missed, so it can flush tlb out of mmu-lock. - * - * So, there is the problem: the first case can meet the corrupted tlb caused - * by another case which write-protects pages but without flush tlb - * immediately. In order to making the first case be aware this problem we let - * it flush tlb if we try to write-protect a spte whose MMU-writable bit - * is set, it works since another case never touches MMU-writable bit. - * - * Anyway, whenever a spte is updated (only permission and status bits are - * changed) we need to check whether the spte with MMU-writable becomes - * readonly, if that happens, we need to flush tlb. Fortunately, - * mmu_spte_update() has already handled it perfectly. - * - * The rules to use MMU-writable and PT_WRITABLE_MASK: - * - if we want to see if it has writable tlb entry or if the spte can be - * writable on the mmu mapping, check MMU-writable, this is the most - * case, otherwise - * - if we fix page fault on the spte or do write-protection by dirty logging, - * check PT_WRITABLE_MASK. - * - * TODO: introduce APIs to split these two cases. - */ -static inline bool is_writable_pte(unsigned long pte) -{ - return pte & PT_WRITABLE_MASK; -} - /* * Check if a given access (described through the I/D, W/R and U/S bits of a * page fault error code pfec) causes a permission fault with the given PTE -- cgit v1.2.3