On Wed, Nov 15, 2023 at 9:26 AM Patrick Venture <vent...@google.com> wrote:
> > > On Wed, Nov 15, 2023 at 9:02 AM Richard Henderson < > richard.hender...@linaro.org> wrote: > >> On 11/15/23 08:58, Patrick Venture wrote: >> > >> > >> > On Wed, Nov 15, 2023 at 2:35 AM Peter Maydell <peter.mayd...@linaro.org >> > <mailto:peter.mayd...@linaro.org>> wrote: >> > >> > On Tue, 14 Nov 2023 at 20:55, Patrick Venture <vent...@google.com >> > <mailto:vent...@google.com>> wrote: >> > > Avoids unaligned pointer issues. >> > > >> > >> > It would be nice to be more specific in the commit message here, by >> > describing what kind of guest behaviour or machine config runs into >> this >> > problem, and whether this happens in a situation users are likely to >> > run into. If the latter, we should consider tagging the commit >> > with "Cc: qemu-sta...@nongnu.org <mailto:qemu-sta...@nongnu.org>" >> to have it >> > backported to the >> > stable release branches. >> > >> > >> > Thanks! I'll update the commit message with v2. We were seeing this in >> our >> > infrastructure with unaligned accesses using the pointer dereference as >> there are no >> > guarantees on alignment of the incoming values. >> >> Which host cpu, for reference? There aren't many that generate unaligned >> traps these days... >> >> > Here's the sanitizer log/qemu log, the host-cpu was an amd64. > AMD ROME > > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.01H:ECX.pcid [bit 17] > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.07H:EBX.erms [bit 9] > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.07H:EBX.invpcid [bit 10] > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.01H:ECX.pcid [bit 17] > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.07H:EBX.erms [bit 9] > qemu-kvm-system-x86_64: warning: host doesn't support requested feature: > CPUID.07H:EBX.invpcid [bit 10] > third_party/qemu/softmmu/memory.c:1341:16: runtime error: load of > misaligned address 0x52500020b10d for type 'uint32_t' (aka 'unsigned int'), > which requires 4 byte alignment > 0x52500020b10d: note: pointer points here > ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab ab > ab ab ab ab ab ab ab ab ab > ^ > #0 0x55b34f8ef9d8 in memory_region_ram_device_read > third_party/qemu/softmmu/memory.c:1341:16 > #1 0x55b34f8ee8a8 in memory_region_read_accessor > third_party/qemu/softmmu/memory.c:441:11 > #2 0x55b34f8e06db in access_with_adjusted_size > third_party/qemu/softmmu/memory.c:569:18 > #3 0x55b34f8dfcb4 in memory_region_dispatch_read1 > third_party/qemu/softmmu/memory.c > #4 0x55b34f8dfcb4 in memory_region_dispatch_read > third_party/qemu/softmmu/memory.c:1476:9 > #5 0x55b34f8fa8b0 in flatview_read_continue > third_party/qemu/softmmu/physmem.c:2744:23 > #6 0x55b34f8fb0db in flatview_read > third_party/qemu/softmmu/physmem.c:2786:12 > #7 0x55b34f8faefa in address_space_read_full > third_party/qemu/softmmu/physmem.c:2799:18 > #8 0x55b34f8fb5b4 in address_space_rw > third_party/qemu/softmmu/physmem.c:2827:16 > #9 0x55b34f71eab5 in kvm_cpu_exec > third_party/qemu/accel/kvm/kvm-all.c:3062:13 > #10 0x55b34f7172e3 in kvm_vcpu_thread_fn > third_party/qemu/accel/kvm/kvm-accel-ops.c:51:17 > #11 0x55b350467044 in qemu_thread_start > third_party/qemu/util/qemu-thread-posix.c:541:9 > #12 0x55b34f6dba10 in asan_thread_start(void*) > third_party/llvm/llvm-project/compiler-rt/lib/asan/asan_interceptors.cpp:234:28 > #13 0x7f5e1c81a7d8 in start_thread > (/usr/grte/v5/lib64/libpthread.so.0+0xb7d8) (BuildId: > 3ccc1600b9140e48da03ed16e0210354) > #14 0x7f5e1c77169e in clone (/usr/grte/v5/lib64/libc.so.6+0x13969e) > (BuildId: 280088eab084c30a3992a9bce5c35b44) > > SUMMARY: UndefinedBehaviorSanitizer: misaligned-pointer-use > third_party/qemu/softmmu/memory.c:1341:16 in > > > > >> >> r~ >> >>
