Subject: [PATCH 08/13] KVM: PPC: Allow I/O mappings in memory slots

From: Paul Mackerras <[email-masked]>
Date: Tue, 6 Dec 2011 17:09:59 +1100

This provides for the case where userspace maps an I/O device into the
address range of a memory slot using a VM_PFNMAP mapping.  In that
case, we work out the pfn from vma->vm_pgoff, and record the cache
enable bits from vma->vm_page_prot in two low-order bits in the
slot_phys array entries.  Then, in kvmppc_h_enter() we check that the
cache bits in the HPTE that the guest wants to insert match the cache
bits in the slot_phys array entry.

Signed-off-by: Paul Mackerras <[email-masked]>
---
 arch/powerpc/include/asm/kvm_book3s_64.h |   26 +++++++++++
 arch/powerpc/include/asm/kvm_host.h      |    2 +
 arch/powerpc/kvm/book3s_64_mmu_hv.c      |   67 ++++++++++++++++++++----------
 arch/powerpc/kvm/book3s_hv_rm_mmu.c      |    5 +-
 4 files changed, 76 insertions(+), 24 deletions(-)

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index d55e6b4..a98e0f6 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -107,6 +107,32 @@ static inline unsigned long hpte_page_size(unsigned long h, unsigned long l)
 	return 0;				/* error */
 }
 
+static inline int hpte_cache_flags_ok(unsigned long ptel, unsigned long io_type)
+{
+	unsigned int wimg = ptel & HPTE_R_WIMG;
+
+	/* Handle SAO */
+	if (wimg == (HPTE_R_W | HPTE_R_I | HPTE_R_M) &&
+	    cpu_has_feature(CPU_FTR_ARCH_206))
+		wimg = HPTE_R_M;
+
+	if (!io_type)
+		return wimg == HPTE_R_M;
+
+	return (wimg & (HPTE_R_W | HPTE_R_I)) == io_type;
+}
+
+/* Return HPTE cache control bits corresponding to Linux pte bits */
+static inline unsigned long hpte_cache_bits(unsigned long pte_val)
+{
+#if _PAGE_NO_CACHE == HPTE_R_I && _PAGE_WRITETHRU == HPTE_R_W
+	return pte_val & (HPTE_R_W | HPTE_R_I);
+#else
+	return ((pte_val & _PAGE_NO_CACHE) ? HPTE_R_I : 0) +
+		((pte_val & _PAGE_WRITETHRU) ? HPTE_R_W : 0);
+#endif
+}
+
 static inline bool slot_is_aligned(struct kvm_memory_slot *memslot,
 				   unsigned long pagesize)
 {
diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
index ba1da85..9b1c247 100644
--- a/arch/powerpc/include/asm/kvm_host.h
+++ b/arch/powerpc/include/asm/kvm_host.h
@@ -177,6 +177,8 @@ struct revmap_entry {
 
 /* Low-order bits in kvm->arch.slot_phys[][] */
 #define KVMPPC_PAGE_ORDER_MASK	0x1f
+#define KVMPPC_PAGE_NO_CACHE	HPTE_R_I	/* 0x20 */
+#define KVMPPC_PAGE_WRITETHRU	HPTE_R_W	/* 0x40 */
 #define KVMPPC_GOT_PAGE		0x80
 
 struct kvm_arch {
diff --git a/arch/powerpc/kvm/book3s_64_mmu_hv.c b/arch/powerpc/kvm/book3s_64_mmu_hv.c
index cc18f3d..b904c40 100644
--- a/arch/powerpc/kvm/book3s_64_mmu_hv.c
+++ b/arch/powerpc/kvm/book3s_64_mmu_hv.c
@@ -199,7 +199,8 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 	struct page *page, *hpage, *pages[1];
 	unsigned long s, pgsize;
 	unsigned long *physp;
-	unsigned int got, pgorder;
+	unsigned int is_io, got, pgorder;
+	struct vm_area_struct *vma;
 	unsigned long pfn, i, npages;
 
 	physp = kvm->arch.slot_phys[memslot->id];
@@ -208,34 +209,51 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 	if (physp[gfn - memslot->base_gfn])
 		return 0;
 
+	is_io = 0;
+	got = 0;
 	page = NULL;
 	pgsize = psize;
+	err = -EINVAL;
 	start = gfn_to_hva_memslot(memslot, gfn);
 
 	/* Instantiate and get the page we want access to */
 	np = get_user_pages_fast(start, 1, 1, pages);
-	if (np != 1)
-		return -EINVAL;
-	page = pages[0];
-	got = KVMPPC_GOT_PAGE;
+	if (np != 1) {
+		/* Look up the vma for the page */
+		down_read(&current->mm->mmap_sem);
+		vma = find_vma(current->mm, start);
+		if (!vma || vma->vm_start > start ||
+		    start + psize > vma->vm_end ||
+		    !(vma->vm_flags & VM_PFNMAP))
+			goto up_err;
+		is_io = hpte_cache_bits(pgprot_val(vma->vm_page_prot));
+		pfn = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
+		/* check alignment of pfn vs. requested page size */
+		if (psize > PAGE_SIZE && (pfn & ((psize >> PAGE_SHIFT) - 1)))
+			goto up_err;
+		up_read(&current->mm->mmap_sem);
 
-	/* See if this is a large page */
-	s = PAGE_SIZE;
-	if (PageHuge(page)) {
-		hpage = compound_head(page);
-		s <<= compound_order(hpage);
-		/* Get the whole large page if slot alignment is ok */
-		if (s > psize && slot_is_aligned(memslot, s) &&
-		    !(memslot->userspace_addr & (s - 1))) {
-			start &= ~(s - 1);
-			pgsize = s;
-			page = hpage;
+	} else {
+		page = pages[0];
+		got = KVMPPC_GOT_PAGE;
+
+		/* See if this is a large page */
+		s = PAGE_SIZE;
+		if (PageHuge(page)) {
+			hpage = compound_head(page);
+			s <<= compound_order(hpage);
+			/* Get the whole large page if slot alignment is ok */
+			if (s > psize && slot_is_aligned(memslot, s) &&
+			    !(memslot->userspace_addr & (s - 1))) {
+				start &= ~(s - 1);
+				pgsize = s;
+				page = hpage;
+			}
 		}
+		if (s < psize)
+			goto out;
+		pfn = page_to_pfn(page);
 	}
-	err = -EINVAL;
-	if (s < psize)
-		goto out;
-	pfn = page_to_pfn(page);
 
 	npages = pgsize >> PAGE_SHIFT;
 	pgorder = __ilog2(npages);
@@ -243,7 +261,8 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 	spin_lock(&kvm->arch.slot_phys_lock);
 	for (i = 0; i < npages; ++i) {
 		if (!physp[i]) {
-			physp[i] = ((pfn + i) << PAGE_SHIFT) + got + pgorder;
+			physp[i] = ((pfn + i) << PAGE_SHIFT) +
+				got + is_io + pgorder;
 			got = 0;
 		}
 	}
@@ -257,6 +276,10 @@ static long kvmppc_get_guest_page(struct kvm *kvm, unsigned long gfn,
 		put_page(page);
 	}
 	return err;
+
+ up_err:
+	up_read(&current->mm->mmap_sem);
+	return err;
 }
 
 /*
diff --git a/arch/powerpc/kvm/book3s_hv_rm_mmu.c b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
index c76305c..88d2add 100644
--- a/arch/powerpc/kvm/book3s_hv_rm_mmu.c
+++ b/arch/powerpc/kvm/book3s_hv_rm_mmu.c
@@ -68,6 +68,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	unsigned long g_ptel = ptel;
 	struct kvm_memory_slot *memslot;
 	unsigned long *physp, pte_size;
+	unsigned long is_io;
 	bool realmode = vcpu->arch.vcore->vcore_state == VCORE_RUNNING;
 
 	psize = hpte_page_size(pteh, ptel);
@@ -95,6 +96,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	pa = *physp;
 	if (!pa)
 		return H_TOO_HARD;
+	is_io = pa & (HPTE_R_I | HPTE_R_W);
 	pte_size = PAGE_SIZE << (pa & KVMPPC_PAGE_ORDER_MASK);
 	pa &= PAGE_MASK;
 
@@ -107,8 +109,7 @@ long kvmppc_h_enter(struct kvm_vcpu *vcpu, unsigned long flags,
 	ptel |= pa;
 
 	/* Check WIMG */
-	if ((ptel & HPTE_R_WIMG) != HPTE_R_M &&
-	    (ptel & HPTE_R_WIMG) != (HPTE_R_W | HPTE_R_I | HPTE_R_M))
+	if (!hpte_cache_flags_ok(ptel, is_io))
 		return H_PARAMETER;
 	pteh &= ~0x60UL;
 	pteh |= HPTE_V_VALID;
-- 
1.7.5.4