From: Bingsong Si <owen...@ucloud.cn> without kvm commit 412a3c41, CPUID(EAX=0xd,ECX=0).EBX always equal to 0 even through guest update xcr0, this will crash legacy guest(e.g., CentOS 6). Below is the call trace on the guest.
[ 0.000000] kernel BUG at mm/bootmem.c:469! [ 0.000000] invalid opcode: 0000 [#1] SMP [ 0.000000] last sysfs file: [ 0.000000] CPU 0 [ 0.000000] Modules linked in: [ 0.000000] [ 0.000000] Pid: 0, comm: swapper Tainted: G --------------- H 2.6.32-279#2 Red Hat KVM [ 0.000000] RIP: 0010:[<ffffffff81c4edc4>] [<ffffffff81c4edc4>] alloc_bootmem_core+0x7b/0x29e [ 0.000000] RSP: 0018:ffffffff81a01cd8 EFLAGS: 00010046 [ 0.000000] RAX: ffffffff81cb1748 RBX: ffffffff81cb1720 RCX: 0000000001000000 [ 0.000000] RDX: 0000000000000040 RSI: 0000000000000000 RDI: ffffffff81cb1720 [ 0.000000] RBP: ffffffff81a01d38 R08: 0000000000000000 R09: 0000000000001000 [ 0.000000] R10: 02008921da802087 R11: 00000000ffff8800 R12: 0000000000000000 [ 0.000000] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000001000000 [ 0.000000] FS: 0000000000000000(0000) GS:ffff880002200000(0000) knlGS:0000000000000000 [ 0.000000] CS: 0010 DS: 0018 ES: 0018 CR0: 0000000080050033 [ 0.000000] CR2: 0000000000000000 CR3: 0000000001a85000 CR4: 00000000001406b0 [ 0.000000] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 0.000000] DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 [ 0.000000] Process swapper (pid: 0, threadinfo ffffffff81a00000, task ffffffff81a8d020) [ 0.000000] Stack: [ 0.000000] 0000000000000002 81a01dd881eaf060 000000007e5fe227 0000000000001001 [ 0.000000] <d> 0000000000000040 0000000000000001 0000006cffffffff 0000000001000000 [ 0.000000] <d> ffffffff81cb1720 0000000000000000 0000000000000000 0000000000000000 [ 0.000000] Call Trace: [ 0.000000] [<ffffffff81c4f074>] ___alloc_bootmem_nopanic+0x8d/0xca [ 0.000000] [<ffffffff81c4f0cf>] ___alloc_bootmem+0x11/0x39 [ 0.000000] [<ffffffff81c4f172>] __alloc_bootmem+0xb/0xd [ 0.000000] [<ffffffff814d42d9>] xsave_cntxt_init+0x249/0x2c0 [ 0.000000] [<ffffffff814e0689>] init_thread_xstate+0x17/0x25 [ 0.000000] [<ffffffff814e0710>] fpu_init+0x79/0xaa [ 0.000000] [<ffffffff814e27e3>] cpu_init+0x301/0x344 [ 0.000000] [<ffffffff81276395>] ? sort+0x155/0x230 [ 0.000000] [<ffffffff81c30cf2>] trap_init+0x24e/0x25f [ 0.000000] [<ffffffff81c2bd73>] start_kernel+0x21c/0x430 [ 0.000000] [<ffffffff81c2b33a>] x86_64_start_reservations+0x125/0x129 [ 0.000000] [<ffffffff81c2b438>] x86_64_start_kernel+0xfa/0x109 [ 0.000000] Code: 03 48 89 f1 49 c1 e8 0c 48 0f af d0 48 c7 c6 00 a6 61 81 48 c7 c7 00 e5 79 81 31 c0 4c 89 74 24 08 e8 f2 d7 89 ff 4d 85 e4 75 04 <0f> 0b eb fe 48 8b 45 c0 48 83 e8 01 48 85 45 c0 74 04 0f 0b eb Signed-off-by: Bingsong Si <owen...@ucloud.cn> Message-Id: <20190822042901.16858-1-owen...@ucloud.cn> Signed-off-by: Eduardo Habkost <ehabk...@redhat.com> --- target/i386/cpu.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index daece62c19..b821132b6a 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -4693,7 +4693,13 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, *ecx = xsave_area_size(x86_cpu_xsave_components(cpu)); *eax = env->features[FEAT_XSAVE_COMP_LO]; *edx = env->features[FEAT_XSAVE_COMP_HI]; - *ebx = xsave_area_size(env->xcr0); + /* + * The initial value of xcr0 and ebx == 0, On host without kvm + * commit 412a3c41(e.g., CentOS 6), the ebx's value always == 0 + * even through guest update xcr0, this will crash some legacy guest + * (e.g., CentOS 6), So set ebx == ecx to workaroud it. + */ + *ebx = kvm_enabled() ? *ecx : xsave_area_size(env->xcr0); } else if (count == 1) { *eax = env->features[FEAT_XSAVE]; } else if (count < ARRAY_SIZE(x86_ext_save_areas)) { -- 2.21.0