[PATCH] powerpc/rtas: Keep MSR RI set when calling RTAS

From: Laurent Dufour
Date: Thu Mar 17 2022 - 07:06:26 EST

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RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32bits
mode (MSR[SF] unset).

The change in MSR is done in enter_rtas() in a relatively complex way,
since the MSR value could be hardcoded.

Furthermore, a panic has been reported when hitting the watchdog interrupt
while running in RTAS, this leads to the following stack trace:

[69244.027433][ C24] watchdog: CPU 24 Hard LOCKUP
[69244.027442][ C24] watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago)
[69244.027451][ C24] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
[69244.027555][ C24] ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
[69244.027587][ C24] Supported: No, Unreleased kernel
[69244.027600][ C24] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G E X 5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
[69244.027609][ C24] NIP: 000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
[69244.027612][ C24] REGS: c00000000fc33d60 TRAP: 0100 Tainted: G E X (5.14.21-150400.71.1.bz196362_2-default)
[69244.027615][ C24] MSR: 8000000002981000 <SF,VEC,VSX,ME> CR: 48800002 XER: 20040020
[69244.027625][ C24] CFAR: 000000000000011c IRQMASK: 1
[69244.027625][ C24] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
[69244.027625][ C24] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
[69244.027625][ C24] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
[69244.027625][ C24] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
[69244.027625][ C24] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
[69244.027625][ C24] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
[69244.027625][ C24] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
[69244.027625][ C24] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
[69244.027663][ C24] NIP [000000001fb41050] 0x1fb41050
[69244.027696][ C24] LR [000000001fb4104c] 0x1fb4104c
[69244.027699][ C24] Call Trace:
[69244.027701][ C24] Instruction dump:
[69244.027723][ C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.027728][ C24] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.027762][T87504] Oops: Unrecoverable System Reset, sig: 6 [#1]
[69244.028044][T87504] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
[69244.028089][T87504] Modules linked in: chacha_generic(E) libchacha(E) xxhash_generic(E) wp512(E) sha3_generic(E) rmd160(E) poly1305_generic(E) libpoly1305(E) michael_mic(E) md4(E) crc32_generic(E) cmac(E) ccm(E) algif_rng(E) twofish_generic(E) twofish_common(E) serpent_generic(E) fcrypt(E) des_generic(E) libdes(E) cast6_generic(E) cast5_generic(E) cast_common(E) camellia_generic(E) blowfish_generic(E) blowfish_common(E) algif_skcipher(E) algif_hash(E) gcm(E) algif_aead(E) af_alg(E) tun(E) rpcsec_gss_krb5(E) auth_rpcgss(E)
nfsv4(E) dns_resolver(E) rpadlpar_io(EX) rpaphp(EX) xsk_diag(E) tcp_diag(E) udp_diag(E) raw_diag(E) inet_diag(E) unix_diag(E) af_packet_diag(E) netlink_diag(E) nfsv3(E) nfs_acl(E) nfs(E) lockd(E) grace(E) sunrpc(E) fscache(E) netfs(E) af_packet(E) rfkill(E) bonding(E) tls(E) ibmveth(EX) crct10dif_vpmsum(E) rtc_generic(E) drm(E) drm_panel_orientation_quirks(E) fuse(E) configfs(E) backlight(E) ip_tables(E) x_tables(E) dm_service_time(E) sd_mod(E) t10_pi(E)
[69244.028171][T87504] ibmvfc(EX) scsi_transport_fc(E) vmx_crypto(E) gf128mul(E) btrfs(E) blake2b_generic(E) libcrc32c(E) crc32c_vpmsum(E) xor(E) raid6_pq(E) dm_mirror(E) dm_region_hash(E) dm_log(E) sg(E) dm_multipath(E) dm_mod(E) scsi_dh_rdac(E) scsi_dh_emc(E) scsi_dh_alua(E) scsi_mod(E)
[69244.028307][T87504] Supported: No, Unreleased kernel
[69244.028385][T87504] CPU: 24 PID: 87504 Comm: drmgr Kdump: loaded Tainted: G E X 5.14.21-150400.71.1.bz196362_2-default #1 SLE15-SP4 (unreleased) 0d821077ef4faa8dfaf370efb5fdca1fa35f4e2c
[69244.028408][T87504] NIP: 000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000
[69244.028418][T87504] REGS: c00000000fc33d60 TRAP: 0100 Tainted: G E X (5.14.21-150400.71.1.bz196362_2-default)
[69244.028429][T87504] MSR: 8000000002981000 <SF,VEC,VSX,ME> CR: 48800002 XER: 20040020
[69244.028444][T87504] CFAR: 000000000000011c IRQMASK: 1
[69244.028444][T87504] GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc
[69244.028444][T87504] GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010
[69244.028444][T87504] GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000
[69244.028444][T87504] GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034
[69244.028444][T87504] GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008
[69244.028444][T87504] GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f
[69244.028444][T87504] GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40
[69244.028444][T87504] GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000
[69244.028534][T87504] NIP [000000001fb41050] 0x1fb41050
[69244.028543][T87504] LR [000000001fb4104c] 0x1fb4104c
[69244.028549][T87504] Call Trace:
[69244.028554][T87504] Instruction dump:
[69244.028561][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.028575][T87504] XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX
[69244.028607][T87504] ---[ end trace 3ddec07f638c34a2 ]---

This happens because MSR[RI] is unset when entering RTAS but there is no
valid reason to not set it here.

Fixing this by reviewing the way MSR is compute before calling RTAS. Now a
hardcoded value meaning real mode, 32 bits and Recoverable Interrupt is
loaded.

In addition a check is added in do_enter_rtas() to detect calls made with
MSR[RI] unset, as we are forcing it on later.

Cc: stable@xxxxxxxxxxxxxxx
Suggested-by: Nicholas Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxx>
---
arch/powerpc/kernel/entry_64.S | 18 ++++++------------
arch/powerpc/kernel/rtas.c | 5 +++++
2 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 9581906b5ee9..fbc8dfe7da9f 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -330,22 +330,16 @@ _GLOBAL(enter_rtas)
clrldi r4,r4,2 /* convert to realmode address */
mtlr r4

- li r0,0
- ori r0,r0,MSR_EE|MSR_SE|MSR_BE|MSR_RI
- andc r0,r6,r0
-
- li r9,1
- rldicr r9,r9,MSR_SF_LG,(63-MSR_SF_LG)
- ori r9,r9,MSR_IR|MSR_DR|MSR_FE0|MSR_FE1|MSR_FP|MSR_RI|MSR_LE
- andc r6,r0,r9
-
__enter_rtas:
- sync /* disable interrupts so SRR0/1 */
- mtmsrd r0 /* don't get trashed */
-
LOAD_REG_ADDR(r4, rtas)
ld r5,RTASENTRY(r4) /* get the rtas->entry value */
ld r4,RTASBASE(r4) /* get the rtas->base value */
+
+ /* RTAS runs in 32bits real mode but we may hit watchdog irq */
+ LOAD_REG_IMMEDIATE(r6, MSR_ME|MSR_RI)
+
+ li r0,0
+ mtmsrd r0,1 /* disable RI before using SRR0/1 */

mtspr SPRN_SRR0,r5
mtspr SPRN_SRR1,r6
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index 1f42aabbbab3..d7775b8c8853 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/arch/powerpc/kernel/rtas.c
@@ -49,6 +49,11 @@ void enter_rtas(unsigned long);

static inline void do_enter_rtas(unsigned long args)
{
+ unsigned long msr;
+
+ msr = mfmsr();
+ BUG_ON(!(msr & MSR_RI));
+
enter_rtas(args);

srr_regs_clobbered(); /* rtas uses SRRs, invalidate */
--
2.35.1

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