KVM: Pass in write/dirty to kvm_vcpu_map(), not kvm_vcpu_unmap()

Now that all kvm_vcpu_{,un}map() users pass "true" for @dirty, have them
pass "true" as a @writable param to kvm_vcpu_map(), and thus create a
read-only mapping when possible.

Note, creating read-only mappings can be theoretically slower, as they
don't play nice with fast GUP due to the need to break CoW before mapping
the underlying PFN.  But practically speaking, creating a mapping isn't
a super hot path, and getting a writable mapping for reading is weird and
confusing.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-34-seanjc@google.com>

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index cf84103ce38b97f2fedc28c426e11a9e31a882f3..b708bdf7eaffd233af174c4f3740716306919c02 100644 (file)
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -926,7 +926,7 @@ out_exit_err:
        nested_svm_vmexit(svm);
 
 out:
-       kvm_vcpu_unmap(vcpu, &map, true);
+       kvm_vcpu_unmap(vcpu, &map);
 
        return ret;
 }
@@ -1130,7 +1130,7 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
                                       vmcb12->control.exit_int_info_err,
                                       KVM_ISA_SVM);
 
-       kvm_vcpu_unmap(vcpu, &map, true);
+       kvm_vcpu_unmap(vcpu, &map);
 
        nested_svm_transition_tlb_flush(vcpu);
 

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0b851ef937f29761d421e4e266c232f3d2e63156..4557ff3804ae27ea6c148405bdf4bdaa2d3a1460 100644 (file)
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3468,7 +3468,7 @@ void sev_es_unmap_ghcb(struct vcpu_svm *svm)
 
        sev_es_sync_to_ghcb(svm);
 
-       kvm_vcpu_unmap(&svm->vcpu, &svm->sev_es.ghcb_map, true);
+       kvm_vcpu_unmap(&svm->vcpu, &svm->sev_es.ghcb_map);
        svm->sev_es.ghcb = NULL;
 }
 

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 9df3e1e5ae81a1346409632edd693cb7e0740f72..c1e29307826bbd4015de3d6b3c8d22429e42bfca 100644 (file)
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2299,7 +2299,7 @@ static int vmload_vmsave_interception(struct kvm_vcpu *vcpu, bool vmload)
                svm_copy_vmloadsave_state(vmcb12, svm->vmcb);
        }
 
-       kvm_vcpu_unmap(vcpu, &map, true);
+       kvm_vcpu_unmap(vcpu, &map);
 
        return ret;
 }
@@ -4714,7 +4714,7 @@ static int svm_enter_smm(struct kvm_vcpu *vcpu, union kvm_smram *smram)
        svm_copy_vmrun_state(map_save.hva + 0x400,
                             &svm->vmcb01.ptr->save);
 
-       kvm_vcpu_unmap(vcpu, &map_save, true);
+       kvm_vcpu_unmap(vcpu, &map_save);
        return 0;
 }
 
@@ -4774,9 +4774,9 @@ static int svm_leave_smm(struct kvm_vcpu *vcpu, const union kvm_smram *smram)
        svm->nested.nested_run_pending = 1;
 
 unmap_save:
-       kvm_vcpu_unmap(vcpu, &map_save, true);
+       kvm_vcpu_unmap(vcpu, &map_save);
 unmap_map:
-       kvm_vcpu_unmap(vcpu, &map, true);
+       kvm_vcpu_unmap(vcpu, &map);
        return ret;
 }
 

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index ff83b56fe2fa218d5e1b264e505a727cf77c572d..259fe445e69520fb240c0f7bcd934b3fb11efc02 100644 (file)
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -231,7 +231,7 @@ static inline void nested_release_evmcs(struct kvm_vcpu *vcpu)
        struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
        struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-       kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map, true);
+       kvm_vcpu_unmap(vcpu, &vmx->nested.hv_evmcs_map);
        vmx->nested.hv_evmcs = NULL;
        vmx->nested.hv_evmcs_vmptr = EVMPTR_INVALID;
 
@@ -318,9 +318,9 @@ static void nested_put_vmcs12_pages(struct kvm_vcpu *vcpu)
 {
        struct vcpu_vmx *vmx = to_vmx(vcpu);
 
-       kvm_vcpu_unmap(vcpu, &vmx->nested.apic_access_page_map, true);
-       kvm_vcpu_unmap(vcpu, &vmx->nested.virtual_apic_map, true);
-       kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map, true);
+       kvm_vcpu_unmap(vcpu, &vmx->nested.apic_access_page_map);
+       kvm_vcpu_unmap(vcpu, &vmx->nested.virtual_apic_map);
+       kvm_vcpu_unmap(vcpu, &vmx->nested.pi_desc_map);
        vmx->nested.pi_desc = NULL;
 }
 
@@ -624,7 +624,7 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
        int msr;
        unsigned long *msr_bitmap_l1;
        unsigned long *msr_bitmap_l0 = vmx->nested.vmcs02.msr_bitmap;
-       struct kvm_host_map msr_bitmap_map;
+       struct kvm_host_map map;
 
        /* Nothing to do if the MSR bitmap is not in use.  */
        if (!cpu_has_vmx_msr_bitmap() ||
@@ -647,10 +647,10 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
                        return true;
        }
 
-       if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->msr_bitmap), &msr_bitmap_map))
+       if (kvm_vcpu_map_readonly(vcpu, gpa_to_gfn(vmcs12->msr_bitmap), &map))
                return false;
 
-       msr_bitmap_l1 = (unsigned long *)msr_bitmap_map.hva;
+       msr_bitmap_l1 = (unsigned long *)map.hva;
 
        /*
         * To keep the control flow simple, pay eight 8-byte writes (sixteen
@@ -714,7 +714,7 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
        nested_vmx_set_intercept_for_msr(vmx, msr_bitmap_l1, msr_bitmap_l0,
                                         MSR_IA32_FLUSH_CMD, MSR_TYPE_W);
 
-       kvm_vcpu_unmap(vcpu, &msr_bitmap_map, false);
+       kvm_vcpu_unmap(vcpu, &map);
 
        vmx->nested.force_msr_bitmap_recalc = false;
 

diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index b4c541fa5a1f9783215a1d4b2ea3055b968dbc9d..101dbf2be1ce41c8949832c3f032c1ee5cf02b68 100644 (file)
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -285,6 +285,7 @@ struct kvm_host_map {
        void *hva;
        kvm_pfn_t pfn;
        kvm_pfn_t gfn;
+       bool writable;
 };
 
 /*
@@ -1311,8 +1312,23 @@ void mark_page_dirty(struct kvm *kvm, gfn_t gfn);
 
 struct kvm_memslots *kvm_vcpu_memslots(struct kvm_vcpu *vcpu);
 struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn);
-int kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map);
-void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty);
+
+int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa, struct kvm_host_map *map,
+                  bool writable);
+void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map);
+
+static inline int kvm_vcpu_map(struct kvm_vcpu *vcpu, gpa_t gpa,
+                              struct kvm_host_map *map)
+{
+       return __kvm_vcpu_map(vcpu, gpa, map, true);
+}
+
+static inline int kvm_vcpu_map_readonly(struct kvm_vcpu *vcpu, gpa_t gpa,
+                                       struct kvm_host_map *map)
+{
+       return __kvm_vcpu_map(vcpu, gpa, map, false);
+}
+
 unsigned long kvm_vcpu_gfn_to_hva(struct kvm_vcpu *vcpu, gfn_t gfn);
 unsigned long kvm_vcpu_gfn_to_hva_prot(struct kvm_vcpu *vcpu, gfn_t gfn, bool *writable);
 int kvm_vcpu_read_guest_page(struct kvm_vcpu *vcpu, gfn_t gfn, void *data, int offset,

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 0d59f47f099e9e713e12405746caa9dd78897fc0..baa741c2b81c4cd1b1e88327a17bbae3308daca0 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3110,7 +3110,8 @@ struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn)
 }
 EXPORT_SYMBOL_GPL(gfn_to_page);
 
-int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
+int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map,
+                  bool writable)
 {
        struct kvm_follow_pfn kfp = {
                .slot = gfn_to_memslot(vcpu->kvm, gfn),
@@ -3124,6 +3125,7 @@ int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
        map->page = NULL;
        map->hva = NULL;
        map->gfn = gfn;
+       map->writable = writable;
 
        map->pfn = kvm_follow_pfn(&kfp);
        if (is_error_noslot_pfn(map->pfn))
@@ -3140,9 +3142,9 @@ int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
 
        return map->hva ? 0 : -EFAULT;
 }
-EXPORT_SYMBOL_GPL(kvm_vcpu_map);
+EXPORT_SYMBOL_GPL(__kvm_vcpu_map);
 
-void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
+void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map)
 {
        if (!map->hva)
                return;
@@ -3154,11 +3156,11 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
                memunmap(map->hva);
 #endif
 
-       if (dirty)
+       if (map->writable)
                kvm_vcpu_mark_page_dirty(vcpu, map->gfn);
 
        if (map->pinned_page) {
-               if (dirty)
+               if (map->writable)
                        kvm_set_page_dirty(map->pinned_page);
                kvm_set_page_accessed(map->pinned_page);
                unpin_user_page(map->pinned_page);