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  1. RHEL
  2. RHEL-68997

kernel: Corruption of AArch64 SVE state

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    • Important
    • 1
    • rhel-sst-arch-hw
    • ssg_platform_enablement
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    • 2
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    • Red Hat Enterprise Linux
    • Virt ARM 25-2
    • Unspecified Release Note Type - Unknown
    • aarch64
    • None

      When running a guest on A64FX, we hit a corruption after several guest reboots. We have at least 2 different reproducers. One where the corruption after more than 1d (RHEL-22598) and the other one (RHEL-67106) where we hit it generally within tens of minutes. After further debug at QEMU level we identified a code section that may be the cause of the corruption in flatview_insert(). If we comment out the memmove call and replace it by individual cell copies, we do not hit the issue anymore.

      static void flatview_insert(FlatView *view, unsigned pos, FlatRange *range)
{
    int i = view->nr;
    if (view->nr == view->nr_allocated)

{         view->nr_allocated = MAX(2 * view->nr, 10);         view->ranges = g_realloc(view->ranges,                                     view->nr_allocated * sizeof(*view->ranges));     }

#if 0
    memmove(view->ranges + pos + 1, view->ranges + pos,
            (view->nr - pos) * sizeof(FlatRange));
#else
     while (i > pos)

{         view->ranges[i] = view->ranges[i - 1];         i--;     }

#endif
    view->ranges[pos] = *range;
    memory_region_ref(range->mr);
    ++view->nr;
}

      So we wonder whether there could be something wrong with the memmove implementation on this A64FX HW. After a dicussion with fweimer@redhat.com, it looks the rhel9 code for the memset/memcpy/memmove selectors in glibc in RHEL 9 check midr for A64FX.

      So this Jira ticket is a request to produce a test build with the A64FX string routines ripped out so that glibc would use the generic implementation, just to see if it removes the issue.

        1. core.qemu-kvm.107.4dce636b39b447b0b5f762e3bc2bbf54.1198381.1733367672000000.zst
          4.32 MB
        2. core.qemu-kvm.107.f100930888404cb6b4af95c55790775a.44227.1734069667000000.zst
          3.14 MB
        3. core.qemu-kvm.107.f796277c40474b8183f98ed9206a4885.20707.1734063368000000.zst
          3.27 MB

              eauger Eric Auger
              eauger Eric Auger
              Arch HW AArch64 Triage Arch HW AArch64 Triage
              Liang Cong Liang Cong
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                Created:
                Updated: