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Re: [PATCH v1.1 03/10] tools/libxg: Drop stale p2m logic from ARM's meminit()



Hi Andrew,

On 12/02/2021 20:01, Andrew Cooper wrote:
Various version of gcc, when compiling with -Og, complain:

   xg_dom_arm.c: In function 'meminit':
   xg_dom_arm.c:420:19: error: 'p2m_size' may be used uninitialized in this 
function [-Werror=maybe-uninitialized]
     420 |     dom->p2m_size = p2m_size;
         |     ~~~~~~~~~~~~~~^~~~~~~~~~

This is actually entirely stale code since ee21f10d70^..97e34ad22d which
removed the 1:1 identity p2m for translated domains.

Drop the write of d->p2m_size, and the p2m_size local variable.  Reposition
the p2m_size field in struct xc_dom_image and correct some stale
documentation.

This change really ought to have been part of the original cleanup series.

No actual change to how ARM domains are constructed.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

Acked-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

---
CC: Ian Jackson <iwj@xxxxxxxxxxxxxx>
CC: Wei Liu <wl@xxxxxxx>
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>

v2:
  * Delete stale p2m_size infrastructure.
---
  tools/include/xenguest.h      | 5 ++---
  tools/libs/guest/xg_dom_arm.c | 5 -----
  2 files changed, 2 insertions(+), 8 deletions(-)

diff --git a/tools/include/xenguest.h b/tools/include/xenguest.h
index 775cf34c04..217022b6e7 100644
--- a/tools/include/xenguest.h
+++ b/tools/include/xenguest.h
@@ -145,6 +145,7 @@ struct xc_dom_image {
       * eventually copied into guest context.
       */
      xen_pfn_t *pv_p2m;
+    xen_pfn_t p2m_size;         /* number of pfns covered by pv_p2m */
/* physical memory
       *
@@ -154,12 +155,10 @@ struct xc_dom_image {
       *
       * An ARM guest has GUEST_RAM_BANKS regions of RAM, with
       * rambank_size[i] pages in each. The lowest RAM address
-     * (corresponding to the base of the p2m arrays above) is stored
-     * in rambase_pfn.
+     * is stored in rambase_pfn.
       */
      xen_pfn_t rambase_pfn;
      xen_pfn_t total_pages;
-    xen_pfn_t p2m_size;         /* number of pfns covered by p2m */
      struct xc_dom_phys *phys_pages;
  #if defined (__arm__) || defined(__aarch64__)
      xen_pfn_t rambank_size[GUEST_RAM_BANKS];
diff --git a/tools/libs/guest/xg_dom_arm.c b/tools/libs/guest/xg_dom_arm.c
index 94948d2b20..b4c24f15fb 100644
--- a/tools/libs/guest/xg_dom_arm.c
+++ b/tools/libs/guest/xg_dom_arm.c
@@ -373,7 +373,6 @@ static int meminit(struct xc_dom_image *dom)
      const uint64_t modsize = dtb_size + ramdisk_size;
      const uint64_t ram128mb = bankbase[0] + (128<<20);
- xen_pfn_t p2m_size;
      uint64_t bank0end;
assert(dom->rambase_pfn << XC_PAGE_SHIFT == bankbase[0]);
@@ -409,16 +408,12 @@ static int meminit(struct xc_dom_image *dom)
ramsize -= banksize; - p2m_size = ( bankbase[i] + banksize - bankbase[0] ) >> XC_PAGE_SHIFT;
-
          dom->rambank_size[i] = banksize >> XC_PAGE_SHIFT;
      }
assert(dom->rambank_size[0] != 0);
      assert(ramsize == 0); /* Too much RAM is rejected above */
- dom->p2m_size = p2m_size;
-
      /* setup initial p2m and allocate guest memory */
      for ( i = 0; i < GUEST_RAM_BANKS && dom->rambank_size[i]; i++ )
      {


--
Julien Grall



 


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