[PATCH RFC v1 9/9] KVM: SVM: Pin SEV pages in MMU during sev_launch_update_data()

[Nikunj A Dadhania]

From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

Pin the memory for the data being passed to launch_update_data()
because it gets encrypted before the guest is first run and must
not be moved which would corrupt it.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
[ * Use kvm_for_each_memslot_in_hva_range() to find slot and iterate
  * Updated sev_pin_memory_in_mmu() error handling.
  * As pinning/unpining pages is handled within MMU, removed
    {get,put}_user(). ]
Signed-off-by: Nikunj A Dadhania <nikunj@xxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 146 +++++++++++++++++++++++++++++++++++++----
 1 file changed, 134 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 7e39320fc65d..1c371268934b 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -22,6 +22,7 @@
 #include <asm/trapnr.h>
 #include <asm/fpu/xcr.h>
 
+#include "mmu.h"
 #include "x86.h"
 #include "svm.h"
 #include "svm_ops.h"
@@ -428,9 +429,93 @@ static void *sev_alloc_pages(struct kvm_sev_info *sev, unsigned long uaddr,
 	return pages;
 }
 
+#define SEV_PFERR_RO (PFERR_USER_MASK)
+#define SEV_PFERR_RW (PFERR_WRITE_MASK | PFERR_USER_MASK)
+
+static struct page **sev_pin_memory_in_mmu(struct kvm *kvm, unsigned long addr,
+					   unsigned long size,
+					   unsigned long *npages)
+{
+	unsigned long hva_start, hva_end, uaddr, end, slot_start, slot_end;
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct interval_tree_node *node;
+	struct kvm_memory_slot *slot;
+	struct kvm_memslots *slots;
+	int idx, ret = 0, i = 0;
+	struct kvm_vcpu *vcpu;
+	struct page **pages;
+	kvm_pfn_t pfn;
+	u32 err_code;
+	gfn_t gfn;
+
+	pages = sev_alloc_pages(sev, addr, size, npages);
+	if (IS_ERR(pages))
+		return pages;
+
+	vcpu = kvm_get_vcpu(kvm, 0);
+	if (mutex_lock_killable(&vcpu->mutex)) {
+		kvfree(pages);
+		return ERR_PTR(-EINTR);
+	}
+
+	vcpu_load(vcpu);
+	idx = srcu_read_lock(&kvm->srcu);
+
+	kvm_mmu_load(vcpu);
+
+	end = addr + (*npages << PAGE_SHIFT);
+	slots = kvm_memslots(kvm);
+
+	kvm_for_each_memslot_in_hva_range(node, slots, addr, end) {
+		slot = container_of(node, struct kvm_memory_slot,
+				    hva_node[slots->node_idx]);
+		slot_start = slot->userspace_addr;
+		slot_end = slot_start + (slot->npages << PAGE_SHIFT);
+		hva_start = max(addr, slot_start);
+		hva_end = min(end, slot_end);
+
+		err_code = (slot->flags & KVM_MEM_READONLY) ?
+			SEV_PFERR_RO : SEV_PFERR_RW;
+
+		for (uaddr = hva_start; uaddr < hva_end; uaddr += PAGE_SIZE) {
+			if (signal_pending(current)) {
+				ret = -ERESTARTSYS;
+				break;
+			}
+
+			if (need_resched())
+				cond_resched();
+
+			/*
+			 * Fault in the page and sev_pin_page() will handle the
+			 * pinning
+			 */
+			gfn = hva_to_gfn_memslot(uaddr, slot);
+			pfn = kvm_mmu_map_tdp_page(vcpu, gfn_to_gpa(gfn),
+						   err_code, PG_LEVEL_4K);
+			if (is_error_noslot_pfn(pfn)) {
+				ret = -EFAULT;
+				break;
+			}
+			pages[i++] = pfn_to_page(pfn);
+		}
+	}
+
+	kvm_mmu_unload(vcpu);
+	srcu_read_unlock(&kvm->srcu, idx);
+	vcpu_put(vcpu);
+	mutex_unlock(&vcpu->mutex);
+
+	if (!ret)
+		return pages;
+
+	kvfree(pages);
+	return ERR_PTR(ret);
+}
+
 static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 				    unsigned long ulen, unsigned long *n,
-				    int write)
+				    int write, bool mmu_usable)
 {
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 	struct pinned_region *region;
@@ -441,6 +526,10 @@ static struct page **sev_pin_memory(struct kvm *kvm, unsigned long uaddr,
 
 	lockdep_assert_held(&kvm->lock);
 
+	/* Use MMU based pinning if possible. */
+	if (mmu_usable)
+		return sev_pin_memory_in_mmu(kvm, uaddr, ulen, n);
+
 	pages = sev_alloc_pages(sev, uaddr, ulen, &npages);
 	if (IS_ERR(pages))
 		return pages;
@@ -558,6 +647,7 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 {
 	unsigned long vaddr, vaddr_end, next_vaddr, npages, pages, size, i;
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	bool mmu_usable = atomic_read(&kvm->online_vcpus) > 0;
 	struct kvm_sev_launch_update_data params;
 	struct sev_data_launch_update_data data;
 	struct page **inpages;
@@ -574,15 +664,18 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	vaddr_end = vaddr + size;
 
 	/* Lock the user memory. */
-	inpages = sev_pin_memory(kvm, vaddr, size, &npages, 1);
+	inpages = sev_pin_memory(kvm, vaddr, size, &npages, 1, mmu_usable);
 	if (IS_ERR(inpages))
 		return PTR_ERR(inpages);
 
 	/*
 	 * Flush (on non-coherent CPUs) before LAUNCH_UPDATE encrypts pages in
 	 * place; the cache may contain the data that was written unencrypted.
+	 * Flushing is automatically handled if the pages can be pinned in the
+	 * MMU.
 	 */
-	sev_clflush_pages(inpages, npages);
+	if (!mmu_usable)
+		sev_clflush_pages(inpages, npages);
 
 	data.reserved = 0;
 	data.handle = sev->handle;
@@ -617,9 +710,14 @@ static int sev_launch_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		set_page_dirty_lock(inpages[i]);
 		mark_page_accessed(inpages[i]);
 	}
-	/* unlock the user pages on error */
+	/*
+	 * unlock the user pages on error, else pages will be unpinned either
+	 * during memslot free path or vm destroy path
+	 */
 	if (ret)
 		sev_unpin_memory(kvm, inpages, npages);
+	else if (mmu_usable)
+		kvfree(inpages);
 	return ret;
 }
 
@@ -1001,11 +1099,11 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 		int len, s_off, d_off;
 
 		/* lock userspace source and destination page */
-		src_p = sev_pin_memory(kvm, vaddr & PAGE_MASK, PAGE_SIZE, &n, 0);
+		src_p = sev_pin_memory(kvm, vaddr & PAGE_MASK, PAGE_SIZE, &n, 0, false);
 		if (IS_ERR(src_p))
 			return PTR_ERR(src_p);
 
-		dst_p = sev_pin_memory(kvm, dst_vaddr & PAGE_MASK, PAGE_SIZE, &n, 1);
+		dst_p = sev_pin_memory(kvm, dst_vaddr & PAGE_MASK, PAGE_SIZE, &n, 1, false);
 		if (IS_ERR(dst_p)) {
 			sev_unpin_memory(kvm, src_p, n);
 			return PTR_ERR(dst_p);
@@ -1057,6 +1155,7 @@ static int sev_dbg_crypt(struct kvm *kvm, struct kvm_sev_cmd *argp, bool dec)
 
 static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 {
+	bool mmu_usable = atomic_read(&kvm->online_vcpus) > 0;
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 	struct sev_data_launch_secret data;
 	struct kvm_sev_launch_secret params;
@@ -1071,15 +1170,18 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
 		return -EFAULT;
 
-	pages = sev_pin_memory(kvm, params.guest_uaddr, params.guest_len, &n, 1);
+	pages = sev_pin_memory(kvm, params.guest_uaddr, params.guest_len, &n, 1, mmu_usable);
 	if (IS_ERR(pages))
 		return PTR_ERR(pages);
 
 	/*
 	 * Flush (on non-coherent CPUs) before LAUNCH_SECRET encrypts pages in
 	 * place; the cache may contain the data that was written unencrypted.
+	 * Flushing is automatically handled if the pages can be pinned in the
+	 * MMU.
 	 */
-	sev_clflush_pages(pages, n);
+	if (!mmu_usable)
+		sev_clflush_pages(pages, n);
 
 	/*
 	 * The secret must be copied into contiguous memory region, lets verify
@@ -1126,8 +1228,15 @@ static int sev_launch_secret(struct kvm *kvm, struct kvm_sev_cmd *argp)
 		set_page_dirty_lock(pages[i]);
 		mark_page_accessed(pages[i]);
 	}
+	/*
+	 * unlock the user pages on error, else pages will be unpinned either
+	 * during memslot free path or vm destroy path
+	 */
 	if (ret)
 		sev_unpin_memory(kvm, pages, n);
+	else if (mmu_usable)
+		kvfree(pages);
+
 	return ret;
 }
 
@@ -1358,7 +1467,7 @@ static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	/* Pin guest memory */
 	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
-				    PAGE_SIZE, &n, 0);
+				    PAGE_SIZE, &n, 0, false);
 	if (IS_ERR(guest_page))
 		return PTR_ERR(guest_page);
 
@@ -1406,6 +1515,10 @@ static int sev_send_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 e_free_hdr:
 	kfree(hdr);
 e_unpin:
+	/*
+	 * unlock the user pages on error, else pages will be unpinned either
+	 * during memslot free path or vm destroy path
+	 */
 	if (ret)
 		sev_unpin_memory(kvm, guest_page, n);
 
@@ -1512,6 +1625,7 @@ static int sev_receive_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 {
+	bool mmu_usable = atomic_read(&kvm->online_vcpus) > 0;
 	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
 	struct kvm_sev_receive_update_data params;
 	struct sev_data_receive_update_data data;
@@ -1555,7 +1669,7 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 
 	/* Pin guest memory */
 	guest_page = sev_pin_memory(kvm, params.guest_uaddr & PAGE_MASK,
-				    PAGE_SIZE, &n, 1);
+				    PAGE_SIZE, &n, 1, mmu_usable);
 	if (IS_ERR(guest_page)) {
 		ret = PTR_ERR(guest_page);
 		goto e_free_trans;
@@ -1564,9 +1678,11 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	/*
 	 * Flush (on non-coherent CPUs) before RECEIVE_UPDATE_DATA, the PSP
 	 * encrypts the written data with the guest's key, and the cache may
-	 * contain dirty, unencrypted data.
+	 * contain dirty, unencrypted data. Flushing is automatically handled if
+	 * the pages can be pinned in the MMU.
 	 */
-	sev_clflush_pages(guest_page, n);
+	if (!mmu_usable)
+		sev_clflush_pages(guest_page, n);
 
 	/* The RECEIVE_UPDATE_DATA command requires C-bit to be always set. */
 	data.guest_address = (page_to_pfn(guest_page[0]) << PAGE_SHIFT) + offset;
@@ -1577,8 +1693,14 @@ static int sev_receive_update_data(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	ret = sev_issue_cmd(kvm, SEV_CMD_RECEIVE_UPDATE_DATA, &data,
 				&argp->error);
 
+	/*
+	 * unlock the user pages on error, else pages will be unpinned either
+	 * during memslot free path or vm destroy path
+	 */
 	if (ret)
 		sev_unpin_memory(kvm, guest_page, n);
+	else if (mmu_usable)
+		kvfree(guest_page);
 
 e_free_trans:
 	kfree(trans);
-- 
2.32.0