KVM: MMU: Don't assume struct page for x86

This patch introduces a gfn_to_pfn() function and corresponding functions like
kvm_release_pfn_dirty().  Using these new functions, we can modify the x86
MMU to no longer assume that it can always get a struct page for any given gfn.

We don't want to eliminate gfn_to_page() entirely because a number of places
assume they can do gfn_to_page() and then kmap() the results.  When we support
IO memory, gfn_to_page() will fail for IO pages although gfn_to_pfn() will
succeed.

This does not implement support for avoiding reference counting for reserved
RAM or for IO memory.  However, it should make those things pretty straight
forward.

Since we're only introducing new common symbols, I don't think it will break
the non-x86 architectures but I haven't tested those.  I've tested Intel,
AMD, NPT, and hugetlbfs with Windows and Linux guests.

[avi: fix overflow when shifting left pfns by adding casts]

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 13 insertions, 13 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 57d872aec663..156fe10288ae 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -247,7 +247,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
 {
         pt_element_t gpte;
         unsigned pte_access;
-        struct page *npage;
+        pfn_t pfn;
         int largepage = vcpu->arch.update_pte.largepage;
 
         gpte = *(const pt_element_t *)pte;
@@ -260,13 +260,13 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
         pte_access = page->role.access & FNAME(gpte_access)(vcpu, gpte);
         if (gpte_to_gfn(gpte) != vcpu->arch.update_pte.gfn)
                 return;
-        npage = vcpu->arch.update_pte.page;
-        if (!npage)
+        pfn = vcpu->arch.update_pte.pfn;
+        if (is_error_pfn(pfn))
                 return;
-        get_page(npage);
+        kvm_get_pfn(pfn);
         mmu_set_spte(vcpu, spte, page->role.access, pte_access, 0, 0,
                      gpte & PT_DIRTY_MASK, NULL, largepage, gpte_to_gfn(gpte),
-                     npage, true);
+                     pfn, true);
 }
 
 /*
@@ -275,7 +275,7 @@ static void FNAME(update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *page,
 static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                          struct guest_walker *walker,
                          int user_fault, int write_fault, int largepage,
-                         int *ptwrite, struct page *page)
+                         int *ptwrite, pfn_t pfn)
 {
         hpa_t shadow_addr;
         int level;
@@ -336,7 +336,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
                                                   walker->pte_gpa[level - 2],
                                                   &curr_pte, sizeof(curr_pte));
                         if (r || curr_pte != walker->ptes[level - 2]) {
-                                kvm_release_page_clean(page);
+                                kvm_release_pfn_clean(pfn);
                                 return NULL;
                         }
                 }
@@ -349,7 +349,7 @@ static u64 *FNAME(fetch)(struct kvm_vcpu *vcpu, gva_t addr,
         mmu_set_spte(vcpu, shadow_ent, access, walker->pte_access & access,
                      user_fault, write_fault,
                      walker->ptes[walker->level-1] & PT_DIRTY_MASK,
-                     ptwrite, largepage, walker->gfn, page, false);
+                     ptwrite, largepage, walker->gfn, pfn, false);
 
         return shadow_ent;
 }
@@ -378,7 +378,7 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
         u64 *shadow_pte;
         int write_pt = 0;
         int r;
-        struct page *page;
+        pfn_t pfn;
         int largepage = 0;
 
         pgprintk("%s: addr %lx err %x\n", __func__, addr, error_code);
@@ -413,20 +413,20 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, gva_t addr,
                         largepage = 1;
                 }
         }
-        page = gfn_to_page(vcpu->kvm, walker.gfn);
+        pfn = gfn_to_pfn(vcpu->kvm, walker.gfn);
         up_read(&current->mm->mmap_sem);
 
         /* mmio */
-        if (is_error_page(page)) {
+        if (is_error_pfn(pfn)) {
                 pgprintk("gfn %x is mmio\n", walker.gfn);
-                kvm_release_page_clean(page);
+                kvm_release_pfn_clean(pfn);
                 return 1;
         }
 
         spin_lock(&vcpu->kvm->mmu_lock);
         kvm_mmu_free_some_pages(vcpu);
         shadow_pte = FNAME(fetch)(vcpu, addr, &walker, user_fault, write_fault,
-                                  largepage, &write_pt, page);
+                                  largepage, &write_pt, pfn);
 
         pgprintk("%s: shadow pte %p %llx ptwrite %d\n", __func__,
                  shadow_pte, *shadow_pte, write_pt);