[PATCH RFC v2 0/3] MAP_POPULATE for device memory

[PATCH RFC v2 0/3] MAP_POPULATE for device memory

[Jarkko Sakkinen]

SGX is weird.  SGX memory is managed outside the core mm.  It doesn't
have a 'struct page' and get_user_pages() doesn't work on it.  Its VMAs
are marked with VM_IO.  So, none of the existing methods for avoiding
page faults work on SGX memory.

This patch set essentially helps extend existing "normal RAM" kernel
ABIs to work for avoiding faults for SGX too.  SGX users want to enjoy
all of the benefits of a delayed allocation policy (better resource use,
overcommit, NUMA affinity) but without the cost of millions of faults.

Jarkko Sakkinen (3):
  mm: Add f_op->populate() for populating memory outside of core mm
  x86/sgx: Export sgx_encl_page_alloc()
  x86/sgx: Implement EAUG population with MAP_POPULATE

 arch/x86/kernel/cpu/sgx/driver.c | 128 +++++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/sgx/encl.c   |  38 +++++++++
 arch/x86/kernel/cpu/sgx/encl.h   |   3 +
 arch/x86/kernel/cpu/sgx/ioctl.c  |  38 ---------
 include/linux/fs.h               |   1 +
 mm/gup.c                         |   9 ++-
 6 files changed, 175 insertions(+), 42 deletions(-)

-- 
2.35.1

[PATCH RFC v2 1/3] mm: Add f_op->populate() for populating memory outside of core mm

[Jarkko Sakkinen]

SGX memory is managed outside the core mm.  It doesn't have a 'struct
page' and get_user_pages() doesn't work on it.  Its VMAs are marked with
VM_IO.  So, none of the existing methods for avoiding page faults work
on SGX memory.

Add f_op->populate() to overcome this issue:

int (*populate)(struct file *, unsigned long start, unsigned long end);

Then in populate_vma_page_range(), allow it to be used in the place of
get_user_pages() for memory that falls outside of its scope.

Suggested-by: Dave Hansen <dave.hansen@linux.intel.com>
Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
v4:
* Reimplement based on Dave's suggestion:
  https://lore.kernel.org/linux-sgx/c3083144-bfc1-3260-164c-e59b2d110df8@intel.com/
* Copy the text from the suggestion as part of the commit message (and
  cover letter).
v3:
-       if (!ret && do_populate && file->f_op->populate)
+       if (!ret && do_populate && file->f_op->populate &&
+           !!(vma->vm_flags & (VM_IO | VM_PFNMAP)))
(reported by Matthew Wilcox)
v2:
-       if (!ret && do_populate)
+       if (!ret && do_populate && file->f_op->populate)
(reported by Jan Harkes)
 include/linux/fs.h | 1 +
 mm/gup.c           | 9 +++++----
 2 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2d892b201b0..54151af88ee0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1993,6 +1993,7 @@ struct file_operations {
 	long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
 	long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
 	int (*mmap) (struct file *, struct vm_area_struct *);
+	int (*populate)(struct file *, unsigned long start, unsigned long end);
 	unsigned long mmap_supported_flags;
 	int (*open) (struct inode *, struct file *);
 	int (*flush) (struct file *, fl_owner_t id);
diff --git a/mm/gup.c b/mm/gup.c
index a9d4d724aef7..66736a188a9c 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -1519,8 +1519,11 @@ long populate_vma_page_range(struct vm_area_struct *vma,
 	 * We made sure addr is within a VMA, so the following will
 	 * not result in a stack expansion that recurses back here.
 	 */
-	return __get_user_pages(mm, start, nr_pages, gup_flags,
-				NULL, NULL, locked);
+	if ((vma->vm_flags & (VM_IO | VM_PFNMAP)) && vma->vm_file->f_op->populate)
+		return vma->vm_file->f_op->populate(vma->vm_file, start, end);
+	else
+		return __get_user_pages(mm, start, nr_pages, gup_flags,
+					NULL, NULL, locked);
 }
 
 /*
@@ -1619,8 +1622,6 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
 		 * range with the first VMA. Also, skip undesirable VMA types.
 		 */
 		nend = min(end, vma->vm_end);
-		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
-			continue;
 		if (nstart < vma->vm_start)
 			nstart = vma->vm_start;
 		/*
-- 
2.35.1

Re: [PATCH RFC v2 1/3] mm: Add f_op->populate() for populating memory outside of core mm

[Jarkko Sakkinen]

On Tue, Mar 08, 2022 at 01:10:01PM +0200, Jarkko Sakkinen wrote:
> @@ -1619,8 +1622,6 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
>  		 * range with the first VMA. Also, skip undesirable VMA types.
>  		 */
>  		nend = min(end, vma->vm_end);
> -		if (vma->vm_flags & (VM_IO | VM_PFNMAP))
> -			continue;
>  		if (nstart < vma->vm_start)
>  			nstart = vma->vm_start;
>  		/*

This was unintended, i.e. leaked into patch by mistake. I'll send an
update. There was one diff missing from staging area.

BR, Jarkko

[PATCH RFC v2 2/3] x86/sgx: Export sgx_encl_page_alloc()

[Jarkko Sakkinen]

Move sgx_encl_page_alloc() to encl.c and export it so that it can be
used in the implementation for MAP_POPULATE, which requires to allocate
new enclave pages.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 arch/x86/kernel/cpu/sgx/encl.c  | 38 +++++++++++++++++++++++++++++++++
 arch/x86/kernel/cpu/sgx/encl.h  |  3 +++
 arch/x86/kernel/cpu/sgx/ioctl.c | 38 ---------------------------------
 3 files changed, 41 insertions(+), 38 deletions(-)

diff --git a/arch/x86/kernel/cpu/sgx/encl.c b/arch/x86/kernel/cpu/sgx/encl.c
index f24a41d3ec70..0256918b2c2f 100644
--- a/arch/x86/kernel/cpu/sgx/encl.c
+++ b/arch/x86/kernel/cpu/sgx/encl.c
@@ -913,6 +913,44 @@ int sgx_encl_test_and_clear_young(struct mm_struct *mm,
 	return ret;
 }
 
+struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
+					  unsigned long offset,
+					  u64 secinfo_flags)
+{
+	struct sgx_encl_page *encl_page;
+	unsigned long prot;
+
+	encl_page = kzalloc(sizeof(*encl_page), GFP_KERNEL);
+	if (!encl_page)
+		return ERR_PTR(-ENOMEM);
+
+	encl_page->desc = encl->base + offset;
+	encl_page->encl = encl;
+
+	prot = _calc_vm_trans(secinfo_flags, SGX_SECINFO_R, PROT_READ)  |
+	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_W, PROT_WRITE) |
+	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_X, PROT_EXEC);
+
+	/*
+	 * TCS pages must always RW set for CPU access while the SECINFO
+	 * permissions are *always* zero - the CPU ignores the user provided
+	 * values and silently overwrites them with zero permissions.
+	 */
+	if ((secinfo_flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
+		prot |= PROT_READ | PROT_WRITE;
+
+	/* Calculate maximum of the VM flags for the page. */
+	encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);
+
+	/*
+	 * At time of allocation, the runtime protection bits are the same
+	 * as the maximum protection bits.
+	 */
+	encl_page->vm_run_prot_bits = encl_page->vm_max_prot_bits;
+
+	return encl_page;
+}
+
 /**
  * sgx_zap_enclave_ptes() - remove PTEs mapping the address from enclave
  * @encl: the enclave
diff --git a/arch/x86/kernel/cpu/sgx/encl.h b/arch/x86/kernel/cpu/sgx/encl.h
index 1b6ce1da7c92..3df0d3faf3a1 100644
--- a/arch/x86/kernel/cpu/sgx/encl.h
+++ b/arch/x86/kernel/cpu/sgx/encl.h
@@ -113,6 +113,9 @@ int sgx_encl_get_backing(struct sgx_encl *encl, unsigned long page_index,
 void sgx_encl_put_backing(struct sgx_backing *backing, bool do_write);
 int sgx_encl_test_and_clear_young(struct mm_struct *mm,
 				  struct sgx_encl_page *page);
+struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
+					  unsigned long offset,
+					  u64 secinfo_flags);
 void sgx_zap_enclave_ptes(struct sgx_encl *encl, unsigned long addr);
 struct sgx_epc_page *sgx_alloc_va_page(void);
 unsigned int sgx_alloc_va_slot(struct sgx_va_page *va_page);
diff --git a/arch/x86/kernel/cpu/sgx/ioctl.c b/arch/x86/kernel/cpu/sgx/ioctl.c
index d8c3c07badb3..3e3ca27a6f72 100644
--- a/arch/x86/kernel/cpu/sgx/ioctl.c
+++ b/arch/x86/kernel/cpu/sgx/ioctl.c
@@ -169,44 +169,6 @@ static long sgx_ioc_enclave_create(struct sgx_encl *encl, void __user *arg)
 	return ret;
 }
 
-static struct sgx_encl_page *sgx_encl_page_alloc(struct sgx_encl *encl,
-						 unsigned long offset,
-						 u64 secinfo_flags)
-{
-	struct sgx_encl_page *encl_page;
-	unsigned long prot;
-
-	encl_page = kzalloc(sizeof(*encl_page), GFP_KERNEL);
-	if (!encl_page)
-		return ERR_PTR(-ENOMEM);
-
-	encl_page->desc = encl->base + offset;
-	encl_page->encl = encl;
-
-	prot = _calc_vm_trans(secinfo_flags, SGX_SECINFO_R, PROT_READ)  |
-	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_W, PROT_WRITE) |
-	       _calc_vm_trans(secinfo_flags, SGX_SECINFO_X, PROT_EXEC);
-
-	/*
-	 * TCS pages must always RW set for CPU access while the SECINFO
-	 * permissions are *always* zero - the CPU ignores the user provided
-	 * values and silently overwrites them with zero permissions.
-	 */
-	if ((secinfo_flags & SGX_SECINFO_PAGE_TYPE_MASK) == SGX_SECINFO_TCS)
-		prot |= PROT_READ | PROT_WRITE;
-
-	/* Calculate maximum of the VM flags for the page. */
-	encl_page->vm_max_prot_bits = calc_vm_prot_bits(prot, 0);
-
-	/*
-	 * At time of allocation, the runtime protection bits are the same
-	 * as the maximum protection bits.
-	 */
-	encl_page->vm_run_prot_bits = encl_page->vm_max_prot_bits;
-
-	return encl_page;
-}
-
 static int sgx_validate_secinfo(struct sgx_secinfo *secinfo)
 {
 	u64 perm = secinfo->flags & SGX_SECINFO_PERMISSION_MASK;
-- 
2.35.1

[PATCH RFC v2 3/3] x86/sgx: Implement EAUG population with MAP_POPULATE

[Jarkko Sakkinen]

With SGX1 an enclave needs to be created with its maximum memory demands
pre-allocated. Pages cannot be added to an enclave after it is initialized.
SGX2 introduces a new function, ENCLS[EAUG] for adding pages to an
initialized enclave.

Add support for dynamically adding pages to an initialized enclave with
mmap() by populating pages with EAUG. Use f_ops->populate() callback to
achieve this behaviour.

Signed-off-by: Jarkko Sakkinen <jarkko@kernel.org>
---
 arch/x86/kernel/cpu/sgx/driver.c | 128 +++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)

diff --git a/arch/x86/kernel/cpu/sgx/driver.c b/arch/x86/kernel/cpu/sgx/driver.c
index aa9b8b868867..848938334e8a 100644
--- a/arch/x86/kernel/cpu/sgx/driver.c
+++ b/arch/x86/kernel/cpu/sgx/driver.c
@@ -9,6 +9,7 @@
 #include <asm/traps.h>
 #include "driver.h"
 #include "encl.h"
+#include "encls.h"
 
 u64 sgx_attributes_reserved_mask;
 u64 sgx_xfrm_reserved_mask = ~0x3;
@@ -101,6 +102,132 @@ static int sgx_mmap(struct file *file, struct vm_area_struct *vma)
 	return 0;
 }
 
+static int sgx_encl_augment_page(struct sgx_encl *encl, unsigned long offset)
+{
+	struct sgx_pageinfo pginfo = {0};
+	struct sgx_encl_page *encl_page;
+	struct sgx_epc_page *epc_page;
+	struct sgx_va_page *va_page;
+	u64 secinfo_flags;
+	int ret;
+
+	/*
+	 * Ignore internal permission checking for dynamically added pages.
+	 * They matter only for data added during the pre-initialization phase.
+	 * The enclave decides the permissions by the means of EACCEPT,
+	 * EACCEPTCOPY and EMODPE.
+	 */
+	secinfo_flags = SGX_SECINFO_R | SGX_SECINFO_W | SGX_SECINFO_X;
+	encl_page = sgx_encl_page_alloc(encl, offset, secinfo_flags);
+	if (IS_ERR(encl_page))
+		return PTR_ERR(encl_page);
+
+	epc_page = sgx_alloc_epc_page(encl_page, true);
+	if (IS_ERR(epc_page)) {
+		ret = PTR_ERR(epc_page);
+		goto err_alloc_epc_page;
+	}
+
+	va_page = sgx_encl_grow(encl);
+	if (IS_ERR(va_page)) {
+		ret = PTR_ERR(va_page);
+		goto err_grow;
+	}
+
+	mutex_lock(&encl->lock);
+
+	/*
+	 * Adding to encl->va_pages must be done under encl->lock.  Ditto for
+	 * deleting (via sgx_encl_shrink()) in the error path.
+	 */
+	if (va_page)
+		list_add(&va_page->list, &encl->va_pages);
+
+	/*
+	 * Insert prior to EADD in case of OOM.  EADD modifies MRENCLAVE, i.e.
+	 * can't be gracefully unwound, while failure on EADD/EXTEND is limited
+	 * to userspace errors (or kernel/hardware bugs).
+	 */
+	ret = xa_insert(&encl->page_array, PFN_DOWN(encl_page->desc),
+			encl_page, GFP_KERNEL);
+
+	/*
+	 * If ret == -EBUSY then page was created in another flow while
+	 * running without encl->lock
+	 */
+	if (ret)
+		goto err_xa_insert;
+
+	pginfo.secs = (unsigned long)sgx_get_epc_virt_addr(encl->secs.epc_page);
+	pginfo.addr = encl_page->desc & PAGE_MASK;
+	pginfo.metadata = 0;
+
+	ret = __eaug(&pginfo, sgx_get_epc_virt_addr(epc_page));
+	if (ret)
+		goto err_eaug;
+
+	encl_page->encl = encl;
+	encl_page->epc_page = epc_page;
+	encl_page->type = SGX_PAGE_TYPE_REG;
+	encl->secs_child_cnt++;
+
+	sgx_mark_page_reclaimable(encl_page->epc_page);
+
+	mutex_unlock(&encl->lock);
+
+	return 0;
+
+err_eaug:
+	xa_erase(&encl->page_array, PFN_DOWN(encl_page->desc));
+
+err_xa_insert:
+	sgx_encl_shrink(encl, va_page);
+	mutex_unlock(&encl->lock);
+
+err_grow:
+	sgx_encl_free_epc_page(epc_page);
+
+err_alloc_epc_page:
+	kfree(encl_page);
+
+	return VM_FAULT_SIGBUS;
+}
+
+/*
+ * Add new pages to the enclave sequentially with ENCLS[EAUG]. Note that
+ * sgx_mmap() validates that the given VMA is within the enclave range. Calling
+ * here sgx_encl_may_map() second time would too time consuming.
+ */
+static int sgx_populate(struct file *file, unsigned long start, unsigned long end)
+{
+	struct sgx_encl *encl = file->private_data;
+	unsigned long length = end - start;
+	unsigned long pos;
+	int ret;
+
+	/* EAUG works only for initialized enclaves. */
+	if (!test_bit(SGX_ENCL_INITIALIZED, &encl->flags))
+		return -EINVAL;
+
+	for (pos = 0 ; pos < length; pos += PAGE_SIZE) {
+		if (signal_pending(current)) {
+			if (!pos)
+				ret = -ERESTARTSYS;
+
+			break;
+		}
+
+		if (need_resched())
+			cond_resched();
+
+		ret = sgx_encl_augment_page(encl, start + pos);
+		if (ret)
+			break;
+	}
+
+	return ret;
+}
+
 static unsigned long sgx_get_unmapped_area(struct file *file,
 					   unsigned long addr,
 					   unsigned long len,
@@ -133,6 +260,7 @@ static const struct file_operations sgx_encl_fops = {
 	.compat_ioctl		= sgx_compat_ioctl,
 #endif
 	.mmap			= sgx_mmap,
+	.populate		= sgx_populate,
 	.get_unmapped_area	= sgx_get_unmapped_area,
 };
 
-- 
2.35.1