Attempting to mmap to a memory mapped IO space returns -1s because the
memory encryption bit is set for these pages. According to the AMD spec,
this bit should not be set for non-DRAM space. The patch checks if this
is an memory IO region being accessed and decrypts accordingly.
Signed-off-by: James Puthukattukaran<james.puthukattuka...@oracle.com>
---
drivers/char/mem.c | 27 +++++++++++++++++++++++++++
1 file changed, 27 insertions(+)
diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index ffeb60d..beaa374 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -355,10 +355,30 @@ static inline int private_mapping_ok(struct
vm_area_struct *vma)
#endif
};
+static int check_flags(struct resource *res, void *arg)
+{
+ int *mmio = arg;
+ *mmio = (!((res->flags & IORESOURCE_SYSTEM_RAM) ==
+ IORESOURCE_SYSTEM_RAM) && (res->desc == IORES_DESC_NONE));
+ return *mmio;
+}
+
+static void check_iomem_region(phys_addr_t addr, size_t size,
+ int *mmio)
+{
+ u64 start, end;
+
+ start = (u64)addr;
+ end = start + size - 1;
+ *mmio = 0;
+ walk_mem_res(start, end, mmio, check_flags);
+}
+
static int mmap_mem(struct file *file, struct vm_area_struct *vma)
{
size_t size = vma->vm_end - vma->vm_start;
phys_addr_t offset = (phys_addr_t)vma->vm_pgoff << PAGE_SHIFT;
+ int mmio;
/* Does it even fit in phys_addr_t? */
if (offset >> PAGE_SHIFT != vma->vm_pgoff)
@@ -387,6 +407,13 @@ static int mmap_mem(struct file *file, struct
vm_area_struct *vma)
vma->vm_ops = &mmap_mem_ops;
+ if (mem_encrypt_active()) {
+ check_iomem_region(vma->vm_pgoff, size, &mmio);
+ if (mmio)
+ vma->vm_page_prot =
+ pgprot_decrypted(vma->vm_page_prot);
+ }
+
/* Remap-pfn-range will mark the range VM_IO */
if (remap_pfn_range(vma,
vma->vm_start,
