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Re: [PATCH] hw/i386/intel_iommu: Simplify vtd_find_as_from_bus_num() log

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH] hw/i386/intel_iommu: Simplify vtd_find_as_from_bus_num() logic
Date: Wed, 26 Feb 2020 19:13:11 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 2/26/20 7:01 PM, Peter Xu wrote:
On Wed, Feb 26, 2020 at 06:49:56PM +0100, Philippe Mathieu-Daudé wrote:
Reorder the if() statement to simplify the function.
This avoid bugs like the one fixed by commit a2e1cd41ccf.

This seems to hint that this patch fixes a problem, but it's pure
refactoring, right?

Pure refactoring yes, I meant: If the code was written this way, we wouldn't had the bug fixed by a2e1cd41ccf.

And I'm not sure about git-diff -w or so, but... I can't apply such a
patch cleanly using "git am".  Are you sure a patch like this would
work (without space change information)?

Ah sorry I didn't think of that (I really thought git-am would apply it).


Signed-off-by: Philippe Mathieu-Daudé <address@hidden>
  hw/i386/intel_iommu.c | 14 ++++++++------
  1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
index 6258c58ac9..e720a8939c 100644
--- a/hw/i386/intel_iommu.c
+++ b/hw/i386/intel_iommu.c
@@ -987,14 +987,17 @@ static bool vtd_slpte_nonzero_rsvd(uint64_t slpte, 
uint32_t level)
  static VTDBus *vtd_find_as_from_bus_num(IntelIOMMUState *s, uint8_t bus_num)
      VTDBus *vtd_bus = s->vtd_as_by_bus_num[bus_num];
-    if (!vtd_bus) {
+    GHashTableIter iter;
+    if (vtd_bus) {
+        return vtd_bus;
+    }
       * Iterate over the registered buses to find the one which
       * currently hold this bus number, and update the bus_num
       * lookup table:
-        GHashTableIter iter;
      g_hash_table_iter_init(&iter, s->vtd_as_by_busptr);
      while (g_hash_table_iter_next(&iter, NULL, (void **)&vtd_bus)) {
          if (pci_bus_num(vtd_bus->bus) == bus_num) {
@@ -1002,9 +1005,8 @@ static VTDBus *vtd_find_as_from_bus_num(IntelIOMMUState 
*s, uint8_t bus_num)
              return vtd_bus;
-        vtd_bus = NULL;
-    }
-    return vtd_bus;
+    return NULL;
/* Given the @iova, get relevant @slptep. @slpte_level will be the last level

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