[RFC 14/16] KVM: Introduce gfn_to_pfn_memslot_protected()

[Kirill A. Shutemov]

The new interface allows to detect if the page is protected.
A protected page cannot be accessed directly by the host: it has to be
mapped manually.

This is preparation for the next patch.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
 arch/powerpc/kvm/book3s_64_mmu_hv.c    |  2 +-
 arch/powerpc/kvm/book3s_64_mmu_radix.c |  2 +-
 arch/x86/kvm/mmu/mmu.c                 |  6 +++--
 include/linux/kvm_host.h               |  2 +-
 virt/kvm/kvm_main.c                    | 35 ++++++++++++++++++--------
 5 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index 2b35f9bcf892..e9a13ecf812f 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -587,7 +587,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	} else {
 		/* Call KVM generic code to do the slow-path check */
 		pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
-					   writing, &write_ok);
+					   writing, &write_ok, NULL);
 		if (is_error_noslot_pfn(pfn))
 			return -EFAULT;
 		page = NULL;
diff --git a/arch/powerpc/kvm/book3s_64_mmu_radix.c b/arch/powerpc/kvm/book3s_64_mmu_radix.c
index aa12cd4078b3..58f8df466a94 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_radix.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_radix.c
@@ -798,7 +798,7 @@ int kvmppc_book3s_instantiate_page(struct kvm_vcpu *vcpu,
 
 		/* Call KVM generic code to do the slow-path check */
 		pfn = __gfn_to_pfn_memslot(memslot, gfn, false, NULL,
-					   writing, upgrade_p);
+					   writing, upgrade_p, NULL);
 		if (is_error_noslot_pfn(pfn))
 			return -EFAULT;
 		page = NULL;
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 8071952e9cf2..0fc095a66a3c 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4096,7 +4096,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
 
 	slot = kvm_vcpu_gfn_to_memslot(vcpu, gfn);
 	async = false;
-	*pfn = __gfn_to_pfn_memslot(slot, gfn, false, &async, write, writable);
+	*pfn = __gfn_to_pfn_memslot(slot, gfn, false, &async, write, writable,
+				    NULL);
 	if (!async)
 		return false; /* *pfn has correct page already */
 
@@ -4110,7 +4111,8 @@ static bool try_async_pf(struct kvm_vcpu *vcpu, bool prefault, gfn_t gfn,
 			return true;
 	}
 
-	*pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL, write, writable);
+	*pfn = __gfn_to_pfn_memslot(slot, gfn, false, NULL, write, writable,
+				    NULL);
 	return false;
 }
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index d7072f6d6aa0..eca18ef9b1f4 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -724,7 +724,7 @@ kvm_pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn);
 kvm_pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn);
 kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
 			       bool atomic, bool *async, bool write_fault,
-			       bool *writable);
+			       bool *writable, bool *protected);
 
 void kvm_release_pfn_clean(kvm_pfn_t pfn);
 void kvm_release_pfn_dirty(kvm_pfn_t pfn);
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 63282def3760..8bcf3201304a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1779,9 +1779,10 @@ static bool hva_to_pfn_fast(unsigned long addr, bool write_fault,
  * 1 indicates success, -errno is returned if error is detected.
  */
 static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
-			   bool *writable, kvm_pfn_t *pfn)
+			   bool *writable, bool *protected, kvm_pfn_t *pfn)
 {
 	unsigned int flags = FOLL_HWPOISON | FOLL_KVM;
+	struct vm_area_struct *vma;
 	struct page *page;
 	int npages = 0;
 
@@ -1795,9 +1796,15 @@ static int hva_to_pfn_slow(unsigned long addr, bool *async, bool write_fault,
 	if (async)
 		flags |= FOLL_NOWAIT;
 
-	npages = get_user_pages_unlocked(addr, 1, &page, flags);
-	if (npages != 1)
+	down_read(&current->mm->mmap_sem);
+	npages = get_user_pages(addr, 1, flags, &page, &vma);
+	if (npages != 1) {
+		up_read(&current->mm->mmap_sem);
 		return npages;
+	}
+	if (protected)
+		*protected = vma_is_kvm_protected(vma);
+	up_read(&current->mm->mmap_sem);
 
 	/* map read fault as writable if possible */
 	if (unlikely(!write_fault) && writable) {
@@ -1888,7 +1895,7 @@ static int hva_to_pfn_remapped(struct vm_area_struct *vma,
  *     whether the mapping is writable.
  */
 static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
-			bool write_fault, bool *writable)
+			bool write_fault, bool *writable, bool *protected)
 {
 	struct vm_area_struct *vma;
 	kvm_pfn_t pfn = 0;
@@ -1903,7 +1910,8 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
 	if (atomic)
 		return KVM_PFN_ERR_FAULT;
 
-	npages = hva_to_pfn_slow(addr, async, write_fault, writable, &pfn);
+	npages = hva_to_pfn_slow(addr, async, write_fault, writable, protected,
+				 &pfn);
 	if (npages == 1)
 		return pfn;
 
@@ -1937,7 +1945,7 @@ static kvm_pfn_t hva_to_pfn(unsigned long addr, bool atomic, bool *async,
 
 kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
 			       bool atomic, bool *async, bool write_fault,
-			       bool *writable)
+			       bool *writable, bool *protected)
 {
 	unsigned long addr = __gfn_to_hva_many(slot, gfn, NULL, write_fault);
 
@@ -1960,7 +1968,7 @@ kvm_pfn_t __gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn,
 	}
 
 	return hva_to_pfn(addr, atomic, async, write_fault,
-			  writable);
+			  writable, protected);
 }
 EXPORT_SYMBOL_GPL(__gfn_to_pfn_memslot);
 
@@ -1968,19 +1976,26 @@ kvm_pfn_t gfn_to_pfn_prot(struct kvm *kvm, gfn_t gfn, bool write_fault,
 		      bool *writable)
 {
 	return __gfn_to_pfn_memslot(gfn_to_memslot(kvm, gfn), gfn, false, NULL,
-				    write_fault, writable);
+				    write_fault, writable, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_prot);
 
 kvm_pfn_t gfn_to_pfn_memslot(struct kvm_memory_slot *slot, gfn_t gfn)
 {
-	return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL);
+	return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot);
 
+static kvm_pfn_t gfn_to_pfn_memslot_protected(struct kvm_memory_slot *slot,
+					      gfn_t gfn, bool *protected)
+{
+	return __gfn_to_pfn_memslot(slot, gfn, false, NULL, true, NULL,
+				    protected);
+}
+
 kvm_pfn_t gfn_to_pfn_memslot_atomic(struct kvm_memory_slot *slot, gfn_t gfn)
 {
-	return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL);
+	return __gfn_to_pfn_memslot(slot, gfn, true, NULL, true, NULL, NULL);
 }
 EXPORT_SYMBOL_GPL(gfn_to_pfn_memslot_atomic);
 
-- 
2.26.2