On 5/23/2025 11:44 PM, Kirill Martynov wrote:
Certain error conditions can trigger x86_cpu_dump_state() to output CPU state
debug information e.g. KVM emulation failure due to misbehaving guest.
However, if the CPU is in System Management Mode (SMM) when the assertion
in cpu_asidx_from_attrs failure happens because:
1. In SMM mode (smm=1), the CPU must use multiple address spaces
with a dedicated SMM address space
2. On machine types with softmmu, address spaces are hardcoded to 1
(no multiple address spaces available)
The assertion occurs in cpu_asidx_from_attrs() when trying to
access memory in SMM mode with insufficient address spaces.
Fix this by:
1. If number of address spaces is 1 always use index 0
2. In other cases use attr.secure for identified proper index
This prevents the assertion while still providing useful debug
output during VM shutdown errors.
To me, it's just a workaround to avoid the assertion.
When attrs.secure is 1, it means it's in SMM mode. As you describe above,
> 1. In SMM mode (smm=1), the CPU must use multiple address spaces
> with a dedicated SMM address space
So I think we need to first figure out why it gets attrs.secure as 1
when there is only 1 address space.
Stack trace of the original issue:
#0 ... in raise () from /lib/x86_64-linux-gnu/libc.so.6
#1 ... in abort () from /lib/x86_64-linux-gnu/libc.so.6
#2 ... in ?? () from /lib/x86_64-linux-gnu/libc.so.6
#3 ... in __assert_fail () from /lib/x86_64-linux-gnu/libc.so.6
#4 ... in cpu_asidx_from_attrs (cpu=cpu@entry=0x5578ca2eb340, attrs=...)
at ../hw/core/cpu-sysemu.c:76
#5 ... in cpu_memory_rw_debug (cpu=cpu@entry=0x5578ca2eb340,
addr=addr@entry=2147258348, ptr=ptr@entry=0x7f5341ca373c, len=len@entry=1,
is_write=is_write@entry=false) at ../softmmu/physmem.c:3529
#6 ... in x86_cpu_dump_state (cs=0x5578ca2eb340,
f=0x7f53434065c0 <_IO_2_1_stderr_>, flags=<optimized out>)
at ../target/i386/cpu-dump.c:560
#7 ... in kvm_cpu_exec (cpu=cpu@entry=0x5578ca2eb340)
at ../accel/kvm/kvm-all.c:3000
#8 ... in kvm_vcpu_thread_fn (arg=arg@entry=0x5578ca2eb340)
at ../accel/kvm/kvm-accel-ops.c:51
#9 ... in qemu_thread_start (args=<optimized out>)
at ../util/qemu-thread-posix.c:505
#10 ... in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0
#11 ... in clone () from /lib/x86_64-linux-gnu/libc.so.6
Signed-off-by: Kirill Martynov <stdcalll...@yandex-team.ru>
---
target/i386/cpu.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/target/i386/cpu.h b/target/i386/cpu.h
index c51e0a43d0..2616a61c87 100644
--- a/target/i386/cpu.h
+++ b/target/i386/cpu.h
@@ -2507,7 +2507,7 @@ void cpu_sync_avx_hflag(CPUX86State *env);
#ifndef CONFIG_USER_ONLY
static inline int x86_asidx_from_attrs(CPUState *cs, MemTxAttrs attrs)
{
- return !!attrs.secure;
+ return cs->num_ases == 1 ? 0 : (!!attrs.secure);
}
static inline AddressSpace *cpu_addressspace(CPUState *cs, MemTxAttrs attrs)
