Some cloud hypervisors do not provide IBPB on very recent CPU processors, including AMD processors affected by Retbleed.

Using IBPB before firmware calls on such systems would cause a GPF at boot like the one below. Do not enable such calls when IBPB support is not present.

[ 0.997530] EFI Variables Facility v0.08 2004-May-17 [ 0.998866] general protection fault, maybe for address 0x1: 0000 [#1] PREEMPT SMP NOPTI [ 1.000393] CPU: 0 PID: 24 Comm: kworker/u2:1 Not tainted 5.19.0-rc8+ #7 [ 1.000393] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 0.0.0 02/06/2015 [ 1.000393] Workqueue: efi_rts_wq efi_call_rts [ 1.000393] RIP: 0010:efi_call_rts+0x66e/0x8a0 [ 1.000393] Code: e8 37 33 58 ff 41 bf 48 00 00 00 49 89 c0 44 89 f9 48 83 c8 01 4c 89 c2 48 c1 ea 20 66 90 b9 49 00 00 00 b8 01 00 00 00 31 d2 <0f> 30 e8 7b 9f 5d ff e8 f6 f8 ff ff 4c 89 f1 4c 89 ea 4c 89 e6 48 [ 1.000393] RSP: 0018:ffffb373800d7e38 EFLAGS: 00010246 [ 1.000393] RAX: 0000000000000001 RBX: 0000000000000006 RCX: 0000000000000049 [ 1.000393] RDX: 0000000000000000 RSI: ffff94fbc19d8fe0 RDI: ffff94fbc1b2b300 [ 1.000393] RBP: ffffb373800d7e70 R08: 0000000000000000 R09: 0000000000000000 [ 1.000393] R10: 000000000000000b R11: 000000000000000b R12: ffffb3738001fd78 [ 1.000393] R13: ffff94fbc2fcfc00 R14: ffffb3738001fd80 R15: 0000000000000048 [ 1.000393] FS: 0000000000000000(0000) GS:ffff94fc3da00000(0000) knlGS:0000000000000000 [ 1.000393] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.000393] CR2: ffff94fc30201000 CR3: 000000006f610000 CR4: 00000000000406f0 [ 1.000393] Call Trace: [ 1.000393] <TASK> [ 1.000393] ? __wake_up+0x13/0x20 [ 1.000393] process_one_work+0x21f/0x3f0 [ 1.000393] worker_thread+0x50/0x3e0 [ 1.000393] ? rescuer_thread+0x3a0/0x3a0 [ 1.000393] kthread+0xee/0x120 [ 1.000393] ? kthread_complete_and_exit+0x20/0x20 [ 1.000393] ret_from_fork+0x22/0x30 [ 1.000393] </TASK> [ 1.000393] Modules linked in: [ 1.037117] ---[ end trace 0000000000000000 ]--- [ 1.038324] RIP: 0010:efi_call_rts+0x66e/0x8a0 [ 1.039650] Code: e8 37 33 58 ff 41 bf 48 00 00 00 49 89 c0 44 89 f9 48 83 c8 01 4c 89 c2 48 c1 ea 20 66 90 b9 49 00 00 00 b8 01 00 00 00 31 d2 <0f> 30 e8 7b 9f 5d ff e8 f6 f8 ff ff 4c 89 f1 4c 89 ea 4c 89 e6 48 [ 1.044235] RSP: 0018:ffffb373800d7e38 EFLAGS: 00010246 [ 1.045513] RAX: 0000000000000001 RBX: 0000000000000006 RCX: 0000000000000049 [ 1.047260] RDX: 0000000000000000 RSI: ffff94fbc19d8fe0 RDI: ffff94fbc1b2b300 [ 1.049014] RBP: ffffb373800d7e70 R08: 0000000000000000 R09: 0000000000000000 [ 1.050762] R10: 000000000000000b R11: 000000000000000b R12: ffffb3738001fd78 [ 1.052521] R13: ffff94fbc2fcfc00 R14: ffffb3738001fd80 R15: 0000000000000048 [ 1.054243] FS: 0000000000000000(0000) GS:ffff94fc3da00000(0000) knlGS:0000000000000000 [ 1.056228] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 1.057632] CR2: ffff94fc30201000 CR3: 000000006f610000 CR4: 00000000000406f0 [ 1.059393] note: kworker/u2:1[24] exited with preempt_count 2

Fixes: 28a99e95f55c ("x86/amd: Use IBPB for firmware calls") Reported-by: Dimitri John Ledkov dimitri.ledkov@canonical.com Signed-off-by: Thadeu Lima de Souza Cascardo cascardo@canonical.com Cc: Peter Zijlstra (Intel) peterz@infradead.org Cc: Borislav Petkov bp@suse.de Cc: stable@vger.kernel.org --- arch/x86/kernel/cpu/bugs.c | 1 + 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 6454bc767f0f..6761668100b9 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1520,6 +1520,7 @@ static void __init spectre_v2_select_mitigation(void) * enable IBRS around firmware calls. */ if (boot_cpu_has_bug(X86_BUG_RETBLEED) && + boot_cpu_has(X86_FEATURE_IBPB) && (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) {