5ca40fcf0d
[ Upstream commit b6b1c3ce06ca438eb24e0f45bf0e63ecad0369f5 ] RTAS runs in real mode (MSR[DR] and MSR[IR] unset) and in 32-bit big endian mode (MSR[SF,LE] 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: watchdog: CPU 24 Hard LOCKUP watchdog: CPU 24 TB:997512652051031, last heartbeat TB:997504470175378 (15980ms ago) ... Supported: No, Unreleased kernel 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 NIP: 000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000 REGS: c00000000fc33d60 TRAP: 0100 Tainted: G E X (5.14.21-150400.71.1.bz196362_2-default) MSR: 8000000002981000 <SF,VEC,VSX,ME> CR: 48800002 XER: 20040020 CFAR: 000000000000011c IRQMASK: 1 GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010 GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000 GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034 GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008 GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40 GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000 NIP [000000001fb41050] 0x1fb41050 LR [000000001fb4104c] 0x1fb4104c Call Trace: Instruction dump: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX Oops: Unrecoverable System Reset, sig: 6 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries ... Supported: No, Unreleased kernel 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 NIP: 000000001fb41050 LR: 000000001fb4104c CTR: 0000000000000000 REGS: c00000000fc33d60 TRAP: 0100 Tainted: G E X (5.14.21-150400.71.1.bz196362_2-default) MSR: 8000000002981000 <SF,VEC,VSX,ME> CR: 48800002 XER: 20040020 CFAR: 000000000000011c IRQMASK: 1 GPR00: 0000000000000003 ffffffffffffffff 0000000000000001 00000000000050dc GPR04: 000000001ffb6100 0000000000000020 0000000000000001 000000001fb09010 GPR08: 0000000020000000 0000000000000000 0000000000000000 0000000000000000 GPR12: 80040000072a40a8 c00000000ff8b680 0000000000000007 0000000000000034 GPR16: 000000001fbf6e94 000000001fbf6d84 000000001fbd1db0 000000001fb3f008 GPR20: 000000001fb41018 ffffffffffffffff 000000000000017f fffffffffffff68f GPR24: 000000001fb18fe8 000000001fb3e000 000000001fb1adc0 000000001fb1cf40 GPR28: 000000001fb26000 000000001fb460f0 000000001fb17f18 000000001fb17000 NIP [000000001fb41050] 0x1fb41050 LR [000000001fb4104c] 0x1fb4104c Call Trace: Instruction dump: XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX ---[ end trace 3ddec07f638c34a2 ]--- This happens because MSR[RI] is unset when entering RTAS but there is no valid reason to not set it here. RTAS is expected to be called with MSR[RI] as specified in PAPR+ section "7.2.1 Machine State": R1–7.2.1–9. If called with MSR[RI] equal to 1, then RTAS must protect its own critical regions from recursion by setting the MSR[RI] bit to 0 when in the critical regions. Fixing this by reviewing the way MSR is compute before calling RTAS. Now a hardcoded value meaning real mode, 32 bits big endian mode and Recoverable Interrupt is loaded. In the case MSR[S] is set, it will remain set while entering RTAS as only urfid can unset it (thanks Fabiano). 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. This patch has been tested on the following machines: Power KVM Guest P8 S822L (host Ubuntu kernel 5.11.0-49-generic) PowerVM LPAR P8 9119-MME (FW860.A1) p9 9008-22L (FW950.00) P10 9080-HEX (FW1010.00) Suggested-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220504101244.12107-1-ldufour@linux.ibm.com Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.