vfio/type1: Chunk contiguous reserved/invalid page mappings

We currently map invalid and reserved pages, such as often occur from
mapping MMIO regions of a VM through the IOMMU, using single pages.
There's really no reason we can't instead follow the methodology we
use for normal pages and find the largest possible physically
contiguous chunk for mapping.  The only difference is that we don't
do locked memory accounting for these since they're not back by RAM.

In most applications this will be a very minor improvement, but when
graphics and GPGPU devices are in play, MMIO BARs become non-trivial.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index e6e7f155bdd9429dafb7c58653b942acae653a50..35c90089478ebc3b70488eb8accaa6b7ed88431e 100644 (file)
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -265,6 +265,7 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
        unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
        bool lock_cap = capable(CAP_IPC_LOCK);
        long ret, i;
+       bool rsvd;
 
        if (!current->mm)
                return -ENODEV;
@@ -273,10 +274,9 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
        if (ret)
                return ret;
 
-       if (is_invalid_reserved_pfn(*pfn_base))
-               return 1;
+       rsvd = is_invalid_reserved_pfn(*pfn_base);
 
-       if (!lock_cap && current->mm->locked_vm + 1 > limit) {
+       if (!rsvd && !lock_cap && current->mm->locked_vm + 1 > limit) {
                put_pfn(*pfn_base, prot);
                pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
                        limit << PAGE_SHIFT);
@@ -284,7 +284,8 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
        }
 
        if (unlikely(disable_hugepages)) {
-               vfio_lock_acct(1);
+               if (!rsvd)
+                       vfio_lock_acct(1);
                return 1;
        }
 
@@ -296,12 +297,14 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
                if (ret)
                        break;
 
-               if (pfn != *pfn_base + i || is_invalid_reserved_pfn(pfn)) {
+               if (pfn != *pfn_base + i ||
+                   rsvd != is_invalid_reserved_pfn(pfn)) {
                        put_pfn(pfn, prot);
                        break;
                }
 
-               if (!lock_cap && current->mm->locked_vm + i + 1 > limit) {
+               if (!rsvd && !lock_cap &&
+                   current->mm->locked_vm + i + 1 > limit) {
                        put_pfn(pfn, prot);
                        pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
                                __func__, limit << PAGE_SHIFT);
@@ -309,7 +312,8 @@ static long vfio_pin_pages(unsigned long vaddr, long npage,
                }
        }
 
-       vfio_lock_acct(i);
+       if (!rsvd)
+               vfio_lock_acct(i);
 
        return i;
 }