[v1,2/3] virtio-balloon: Better names for offset variables in inflate/deflate code
diff mbox series

Message ID 20190719160120.26581-3-david@redhat.com
State New
Headers show
Series
  • virtio-balloon: PartialBalloonedPage rework
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Commit Message

David Hildenbrand July 19, 2019, 4:01 p.m. UTC
"host_page_base" is really confusing, let's make this clearer, also
rename the other offsets to indicate to which base they apply.

offset -> mr_offset
ram_offset -> rb_offset
host_page_base -> rb_aligned_offset

While at it, use QEMU_ALIGN_DOWN() instead of a handcrafted computation
and move the computation to the place where it is needed.

Signed-off-by: David Hildenbrand <david@redhat.com>
---
 hw/virtio/virtio-balloon.c | 26 +++++++++++++-------------
 1 file changed, 13 insertions(+), 13 deletions(-)

Comments

David Gibson July 22, 2019, 2:29 a.m. UTC | #1
On Fri, Jul 19, 2019 at 06:01:19PM +0200, David Hildenbrand wrote:
> "host_page_base" is really confusing, let's make this clearer, also
> rename the other offsets to indicate to which base they apply.
> 
> offset -> mr_offset
> ram_offset -> rb_offset
> host_page_base -> rb_aligned_offset
> 
> While at it, use QEMU_ALIGN_DOWN() instead of a handcrafted computation
> and move the computation to the place where it is needed.
> 
> Signed-off-by: David Hildenbrand <david@redhat.com>

Acked-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  hw/virtio/virtio-balloon.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> index 287d5d4c97..29cee344b2 100644
> --- a/hw/virtio/virtio-balloon.c
> +++ b/hw/virtio/virtio-balloon.c
> @@ -47,24 +47,23 @@ static void virtio_balloon_reset_pbp(VirtIOBalloon *balloon)
>  }
>  
>  static void balloon_inflate_page(VirtIOBalloon *balloon,
> -                                 MemoryRegion *mr, hwaddr offset)
> +                                 MemoryRegion *mr, hwaddr mr_offset)
>  {
> -    void *addr = memory_region_get_ram_ptr(mr) + offset;
> +    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
> +    ram_addr_t rb_offset, rb_aligned_offset;
>      RAMBlock *rb;
>      size_t rb_page_size;
>      int subpages;
> -    ram_addr_t ram_offset, host_page_base;
>  
>      /* XXX is there a better way to get to the RAMBlock than via a
>       * host address? */
> -    rb = qemu_ram_block_from_host(addr, false, &ram_offset);
> +    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
>      rb_page_size = qemu_ram_pagesize(rb);
> -    host_page_base = ram_offset & ~(rb_page_size - 1);
>  
>      if (rb_page_size == BALLOON_PAGE_SIZE) {
>          /* Easy case */
>  
> -        ram_block_discard_range(rb, ram_offset, rb_page_size);
> +        ram_block_discard_range(rb, rb_offset, rb_page_size);
>          /* We ignore errors from ram_block_discard_range(), because it
>           * has already reported them, and failing to discard a balloon
>           * page is not fatal */
> @@ -80,11 +79,12 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
>      warn_report_once(
>  "Balloon used with backing page size > 4kiB, this may not be reliable");
>  
> +    rb_aligned_offset = QEMU_ALIGN_DOWN(rb_offset, rb_page_size);
>      subpages = rb_page_size / BALLOON_PAGE_SIZE;
>  
>      if (balloon->pbp
>          && (rb != balloon->pbp->rb
> -            || host_page_base != balloon->pbp->base)) {
> +            || rb_aligned_offset != balloon->pbp->base)) {
>          /* We've partially ballooned part of a host page, but now
>           * we're trying to balloon part of a different one.  Too hard,
>           * give up on the old partial page */
> @@ -96,10 +96,10 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
>          size_t bitlen = BITS_TO_LONGS(subpages) * sizeof(unsigned long);
>          balloon->pbp = g_malloc0(sizeof(PartiallyBalloonedPage) + bitlen);
>          balloon->pbp->rb = rb;
> -        balloon->pbp->base = host_page_base;
> +        balloon->pbp->base = rb_aligned_offset;
>      }
>  
> -    set_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
> +    set_bit((rb_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
>              balloon->pbp->bitmap);
>  
>      if (bitmap_full(balloon->pbp->bitmap, subpages)) {
> @@ -116,18 +116,18 @@ static void balloon_inflate_page(VirtIOBalloon *balloon,
>  }
>  
>  static void balloon_deflate_page(VirtIOBalloon *balloon,
> -                                 MemoryRegion *mr, hwaddr offset)
> +                                 MemoryRegion *mr, hwaddr mr_offset)
>  {
> -    void *addr = memory_region_get_ram_ptr(mr) + offset;
> +    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
> +    ram_addr_t rb_offset;
>      RAMBlock *rb;
>      size_t rb_page_size;
> -    ram_addr_t ram_offset;
>      void *host_addr;
>      int ret;
>  
>      /* XXX is there a better way to get to the RAMBlock than via a
>       * host address? */
> -    rb = qemu_ram_block_from_host(addr, false, &ram_offset);
> +    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
>      rb_page_size = qemu_ram_pagesize(rb);
>  
>      if (balloon->pbp) {

Patch
diff mbox series

diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
index 287d5d4c97..29cee344b2 100644
--- a/hw/virtio/virtio-balloon.c
+++ b/hw/virtio/virtio-balloon.c
@@ -47,24 +47,23 @@  static void virtio_balloon_reset_pbp(VirtIOBalloon *balloon)
 }
 
 static void balloon_inflate_page(VirtIOBalloon *balloon,
-                                 MemoryRegion *mr, hwaddr offset)
+                                 MemoryRegion *mr, hwaddr mr_offset)
 {
-    void *addr = memory_region_get_ram_ptr(mr) + offset;
+    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
+    ram_addr_t rb_offset, rb_aligned_offset;
     RAMBlock *rb;
     size_t rb_page_size;
     int subpages;
-    ram_addr_t ram_offset, host_page_base;
 
     /* XXX is there a better way to get to the RAMBlock than via a
      * host address? */
-    rb = qemu_ram_block_from_host(addr, false, &ram_offset);
+    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
     rb_page_size = qemu_ram_pagesize(rb);
-    host_page_base = ram_offset & ~(rb_page_size - 1);
 
     if (rb_page_size == BALLOON_PAGE_SIZE) {
         /* Easy case */
 
-        ram_block_discard_range(rb, ram_offset, rb_page_size);
+        ram_block_discard_range(rb, rb_offset, rb_page_size);
         /* We ignore errors from ram_block_discard_range(), because it
          * has already reported them, and failing to discard a balloon
          * page is not fatal */
@@ -80,11 +79,12 @@  static void balloon_inflate_page(VirtIOBalloon *balloon,
     warn_report_once(
 "Balloon used with backing page size > 4kiB, this may not be reliable");
 
+    rb_aligned_offset = QEMU_ALIGN_DOWN(rb_offset, rb_page_size);
     subpages = rb_page_size / BALLOON_PAGE_SIZE;
 
     if (balloon->pbp
         && (rb != balloon->pbp->rb
-            || host_page_base != balloon->pbp->base)) {
+            || rb_aligned_offset != balloon->pbp->base)) {
         /* We've partially ballooned part of a host page, but now
          * we're trying to balloon part of a different one.  Too hard,
          * give up on the old partial page */
@@ -96,10 +96,10 @@  static void balloon_inflate_page(VirtIOBalloon *balloon,
         size_t bitlen = BITS_TO_LONGS(subpages) * sizeof(unsigned long);
         balloon->pbp = g_malloc0(sizeof(PartiallyBalloonedPage) + bitlen);
         balloon->pbp->rb = rb;
-        balloon->pbp->base = host_page_base;
+        balloon->pbp->base = rb_aligned_offset;
     }
 
-    set_bit((ram_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
+    set_bit((rb_offset - balloon->pbp->base) / BALLOON_PAGE_SIZE,
             balloon->pbp->bitmap);
 
     if (bitmap_full(balloon->pbp->bitmap, subpages)) {
@@ -116,18 +116,18 @@  static void balloon_inflate_page(VirtIOBalloon *balloon,
 }
 
 static void balloon_deflate_page(VirtIOBalloon *balloon,
-                                 MemoryRegion *mr, hwaddr offset)
+                                 MemoryRegion *mr, hwaddr mr_offset)
 {
-    void *addr = memory_region_get_ram_ptr(mr) + offset;
+    void *addr = memory_region_get_ram_ptr(mr) + mr_offset;
+    ram_addr_t rb_offset;
     RAMBlock *rb;
     size_t rb_page_size;
-    ram_addr_t ram_offset;
     void *host_addr;
     int ret;
 
     /* XXX is there a better way to get to the RAMBlock than via a
      * host address? */
-    rb = qemu_ram_block_from_host(addr, false, &ram_offset);
+    rb = qemu_ram_block_from_host(addr, false, &rb_offset);
     rb_page_size = qemu_ram_pagesize(rb);
 
     if (balloon->pbp) {