Re: [PATCH v2 4/4] swiotlb: Free tbl memory in swiotlb_exit()

[Konrad Rzeszutek Wilk <konrad@darnok.org>]

On Sat, Jul 31, 2021 at 11:26:11AM -0700, Guenter Roeck wrote:
> Hi,
> 
> On Tue, Jul 20, 2021 at 02:38:26PM +0100, Will Deacon wrote:
> > Although swiotlb_exit() frees the 'slots' metadata array referenced by
> > 'io_tlb_default_mem', it leaves the underlying buffer pages allocated
> > despite no longer being usable.
> > 
> > Extend swiotlb_exit() to free the buffer pages as well as the slots
> > array.
> > 
> 
> This patch causes qemu pseries emulations to crash. Backtrace and bisect
> log see below. Reverting it fixes the problem.

I am 99% sure it is fixed by this patch (which should be in linux-next
in 5 minutes):


From a449ffaf9181b5a2dc705d8a06b13e0068207fd4 Mon Sep 17 00:00:00 2001
From: Will Deacon <will@kernel.org>
Date: Fri, 30 Jul 2021 12:42:31 +0100
Subject: [PATCH] powerpc/svm: Don't issue ultracalls if !mem_encrypt_active()

Commit ad6c00283163 ("swiotlb: Free tbl memory in swiotlb_exit()")
introduced a set_memory_encrypted() call to swiotlb_exit() so that the
buffer pages are returned to an encrypted state prior to being freed.

Sachin reports that this leads to the following crash on a Power server:

[    0.010799] software IO TLB: tearing down default memory pool
[    0.010805] ------------[ cut here ]------------
[    0.010808] kernel BUG at arch/powerpc/kernel/interrupt.c:98!

Nick spotted that this is because set_memory_encrypted() is issuing an
ultracall which doesn't exist for the processor, and should therefore
be gated by mem_encrypt_active() to mirror the x86 implementation.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Claire Chang <tientzu@chromium.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Robin Murphy <robin.murphy@arm.com>
Fixes: ad6c00283163 ("swiotlb: Free tbl memory in swiotlb_exit()")
Suggested-by: Nicholas Piggin <npiggin@gmail.com>
Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com>
Tested-by: Nathan Chancellor <nathan@kernel.org>
Link: https://lore.kernel.org/r/1905CD70-7656-42AE-99E2-A31FC3812EAC@linux.vnet.ibm.com/
Signed-off-by: Will Deacon <will@kernel.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad@kernel.org>
---
 arch/powerpc/platforms/pseries/svm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/powerpc/platforms/pseries/svm.c b/arch/powerpc/platforms/pseries/svm.c
index 1d829e257996..87f001b4c4e4 100644
--- a/arch/powerpc/platforms/pseries/svm.c
+++ b/arch/powerpc/platforms/pseries/svm.c
@@ -63,6 +63,9 @@ void __init svm_swiotlb_init(void)
 
 int set_memory_encrypted(unsigned long addr, int numpages)
 {
+	if (!mem_encrypt_active())
+		return 0;
+
 	if (!PAGE_ALIGNED(addr))
 		return -EINVAL;
 
@@ -73,6 +76,9 @@ int set_memory_encrypted(unsigned long addr, int numpages)
 
 int set_memory_decrypted(unsigned long addr, int numpages)
 {
+	if (!mem_encrypt_active())
+		return 0;
+
 	if (!PAGE_ALIGNED(addr))
 		return -EINVAL;
 
-- 
2.31.1

> 
> Guenter
> 
> ---
> Crash log:
> 
> ...
> [    0.937801][    T1] software IO TLB: tearing down default memory pool
> [    0.938939][    T1] ------------[ cut here ]------------
> [    0.940331][    T1] kernel BUG at arch/powerpc/kernel/interrupt.c:98!
> [    0.940787][    T1] Oops: Exception in kernel mode, sig: 5 [#1]
> [    0.940883][    T1] BE PAGE_SIZE=64K MMU=Radix SMP NR_CPUS=2048 NUMA pSeries
> [    0.940999][    T1] Modules linked in:
> [    0.941240][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.14.0-rc3-next-20210729 #1
> [    0.941523][    T1] NIP:  c000000000031310 LR: c0000000000312f4 CTR: c00000000000c5f0
> [    0.941608][    T1] REGS: c000000008687ac0 TRAP: 0700   Not tainted  (5.14.0-rc3-next-20210729)
> [    0.941795][    T1] MSR:  8000000000029032 <SF,EE,ME,IR,DR,RI>  CR: 24002222  XER: 00000000
> [    0.942031][    T1] CFAR: c000000000300360 IRQMASK: 3
> [    0.942031][    T1] GPR00: c0000000000312f4 c000000008687d60 c0000000022ee300 0000000000000003
> [    0.942031][    T1] GPR04: 000000000000033f 0000000000000400 0000000000000000 000000003e5a0000
> [    0.942031][    T1] GPR08: 000000003e5a0000 0000000000000001 0000000000000000 0000000000000003
> [    0.942031][    T1] GPR12: ffffffffffffffff c000000002fb0000 c0000000000129c0 0000000000000000
> [    0.942031][    T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    0.942031][    T1] GPR20: 0000000000000000 0000000000000000 0000000000000000 c0000000021d8b00
> [    0.942031][    T1] GPR24: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000400
> [    0.942031][    T1] GPR28: 000000000000033f 000000000000f134 c00000000176c068 c000000008687e80
> [    0.942884][    T1] NIP [c000000000031310] .system_call_exception+0x70/0x2d0
> [    0.943399][    T1] LR [c0000000000312f4] .system_call_exception+0x54/0x2d0
> [    0.943594][    T1] Call Trace:
> [    0.943667][    T1] [c000000008687d60] [c0000000000312f4] .system_call_exception+0x54/0x2d0 (unreliable)
> [    0.943919][    T1] [c000000008687e10] [c00000000000c6e4] system_call_common+0xf4/0x258
> [    0.944066][    T1] --- interrupt: c00 at .ucall_norets+0x4/0x14
> [    0.944172][    T1] NIP:  c000000000079ce0 LR: c0000000000fa274 CTR: 0000000000000000
> [    0.944245][    T1] REGS: c000000008687e80 TRAP: 0c00   Not tainted  (5.14.0-rc3-next-20210729)
> [    0.944323][    T1] MSR:  8000000002009032 <SF,VEC,EE,ME,IR,DR,RI>  CR: 24002222  XER: 00000000
> [    0.944463][    T1] IRQMASK: 0
> [    0.944463][    T1] GPR00: c00000000176c068 c000000008687a30 c0000000022ee300 000000000000f134
> [    0.944463][    T1] GPR04: 000000000000033f 0000000000000400 ffffffffffffffff 0000000000000000
> [    0.944463][    T1] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    0.944463][    T1] GPR12: 0000000000000000 c000000002fb0000 c0000000000129c0 0000000000000000
> [    0.944463][    T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    0.944463][    T1] GPR20: 0000000000000000 0000000000000000 0000000000000000 c0000000021d8b00
> [    0.944463][    T1] GPR24: c0000000017c1088 0000000000000004 c00000000171c450 c000000002338e40
> [    0.944463][    T1] GPR28: c0000000017c10b0 c0000000033f0000 0000000000000400 c0000000033f0000
> [    0.945188][    T1] NIP [c000000000079ce0] .ucall_norets+0x4/0x14
> [    0.945285][    T1] LR [c0000000000fa274] .set_memory_encrypted+0x44/0x80
> [    0.945375][    T1] --- interrupt: c00
> [    0.945419][    T1] [c000000008687a30] [c00000000176c068] .swiotlb_exit+0xbc/0x180 (unreliable)
> [    0.945612][    T1] Instruction dump:
> [    0.945745][    T1] 7cbb2b78 7cda3378 7cf93b78 7d184378 482cefd1 60000000 e93f0108 692a0002
> [    0.945883][    T1] 794affe2 0b0a0000 69294000 792997e2 <0b090000> e93f0138 792907e0 0b090000
> [    0.946751][    T1] ---[ end trace 600e218cfc83c24b ]---
> [    0.955185][    T1]
> [    1.955805][    T1] BUG: sleeping function called from invalid context at ./include/linux/percpu-rwsem.h:49
> [    1.955918][    T1] in_atomic(): 0, irqs_disabled(): 1, non_block: 0, pid: 1, name: swapper/0
> [    1.956024][    T1] INFO: lockdep is turned off.
> [    1.956094][    T1] irq event stamp: 14792
> [    1.956142][    T1] hardirqs last  enabled at (14791): [<c0000000001f8fe8>] .__up_console_sem+0xc8/0x110
> [    1.956269][    T1] hardirqs last disabled at (14792): [<c0000000000312f4>] .system_call_exception+0x54/0x2d0
> [    1.956384][    T1] softirqs last  enabled at (10586): [<c000000000efd6d4>] .release_sock+0xb4/0x100
> [    1.956497][    T1] softirqs last disabled at (10584): [<c000000000efd654>] .release_sock+0x34/0x100
> [    1.956726][    T1] CPU: 0 PID: 1 Comm: swapper/0 Tainted: G      D           5.14.0-rc3-next-20210729 #1
> [    1.956846][    T1] Call Trace:
> [    1.956885][    T1] [c000000008687700] [c0000000009fe088] .dump_stack_lvl+0xa4/0x100 (unreliable)
> [    1.957011][    T1] [c000000008687790] [c000000000193060] .___might_sleep+0x2b0/0x2f0
> [    1.957130][    T1] [c000000008687820] [c00000000015fba0] .exit_signals+0x50/0x540
> [    1.957238][    T1] [c0000000086878e0] [c000000000148dbc] .do_exit+0xec/0xe20
> [    1.957335][    T1] [c0000000086879c0] [c000000000029bc4] .oops_end+0x144/0x210
> [    1.957441][    T1] [c000000008687a50] [c0000000000095d4] program_check_common_virt+0x2d4/0x320
> [    1.957561][    T1] --- interrupt: 700 at .system_call_exception+0x70/0x2d0
> [    1.957645][    T1] NIP:  c000000000031310 LR: c0000000000312f4 CTR: c00000000000c5f0
> [    1.957715][    T1] REGS: c000000008687ac0 TRAP: 0700   Tainted: G      D            (5.14.0-rc3-next-20210729)
> [    1.957799][    T1] MSR:  8000000000029032 <SF,EE,ME,IR,DR,RI>  CR: 24002222  XER: 00000000
> [    1.957919][    T1] CFAR: c000000000300360 IRQMASK: 3
> [    1.957919][    T1] GPR00: c0000000000312f4 c000000008687d60 c0000000022ee300 0000000000000003
> [    1.957919][    T1] GPR04: 000000000000033f 0000000000000400 0000000000000000 000000003e5a0000
> [    1.957919][    T1] GPR08: 000000003e5a0000 0000000000000001 0000000000000000 0000000000000003
> [    1.957919][    T1] GPR12: ffffffffffffffff c000000002fb0000 c0000000000129c0 0000000000000000
> [    1.957919][    T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    1.957919][    T1] GPR20: 0000000000000000 0000000000000000 0000000000000000 c0000000021d8b00
> [    1.957919][    T1] GPR24: 0000000000000000 0000000000000000 ffffffffffffffff 0000000000000400
> [    1.957919][    T1] GPR28: 000000000000033f 000000000000f134 c00000000176c068 c000000008687e80
> [    1.958633][    T1] NIP [c000000000031310] .system_call_exception+0x70/0x2d0
> [    1.958720][    T1] LR [c0000000000312f4] .system_call_exception+0x54/0x2d0
> [    1.958803][    T1] --- interrupt: 700
> [    1.958842][    T1] [c000000008687e10] [c00000000000c6e4] system_call_common+0xf4/0x258
> [    1.958961][    T1] --- interrupt: c00 at .ucall_norets+0x4/0x14
> [    1.959055][    T1] NIP:  c000000000079ce0 LR: c0000000000fa274 CTR: 0000000000000000
> [    1.959127][    T1] REGS: c000000008687e80 TRAP: 0c00   Tainted: G      D            (5.14.0-rc3-next-20210729)
> [    1.959210][    T1] MSR:  8000000002009032 <SF,VEC,EE,ME,IR,DR,RI>  CR: 24002222  XER: 00000000
> [    1.959337][    T1] IRQMASK: 0
> [    1.959337][    T1] GPR00: c00000000176c068 c000000008687a30 c0000000022ee300 000000000000f134
> [    1.959337][    T1] GPR04: 000000000000033f 0000000000000400 ffffffffffffffff 0000000000000000
> [    1.959337][    T1] GPR08: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    1.959337][    T1] GPR12: 0000000000000000 c000000002fb0000 c0000000000129c0 0000000000000000
> [    1.959337][    T1] GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> [    1.959337][    T1] GPR20: 0000000000000000 0000000000000000 0000000000000000 c0000000021d8b00
> [    1.959337][    T1] GPR24: c0000000017c1088 0000000000000004 c00000000171c450 c000000002338e40
> [    1.959337][    T1] GPR28: c0000000017c10b0 c0000000033f0000 0000000000000400 c0000000033f0000
> [    1.960042][    T1] NIP [c000000000079ce0] .ucall_norets+0x4/0x14
> [    1.960137][    T1] LR [c0000000000fa274] .set_memory_encrypted+0x44/0x80
> [    1.960219][    T1] --- interrupt: c00
> [    1.960257][    T1] [c000000008687a30] [c00000000176c068] .swiotlb_exit+0xbc/0x180 (unreliable)
> [    1.960845][    T1] Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000005
> qemu-system-ppc64: OS terminated: OS panic: Attempted to kill init! exitcode=0x00000005
> 
> ---
> Bisect log:
> 
> # bad: [8d4b477da1a807199ca60e0829357ce7aa6758d5] Add linux-next specific files for 20210730
> # good: [ff1176468d368232b684f75e82563369208bc371] Linux 5.14-rc3
> git bisect start 'HEAD' 'v5.14-rc3'
> # bad: [8f3eb1f5c702ef868d89799b03c21d122f2fe197] Merge remote-tracking branch 'bpf-next/for-next'
> git bisect bad 8f3eb1f5c702ef868d89799b03c21d122f2fe197
> # good: [02afbb8f68dc8b37c07e457d2f69d440781af23a] Merge remote-tracking branch 'cifsd/cifsd-for-next'
> git bisect good 02afbb8f68dc8b37c07e457d2f69d440781af23a
> # good: [3e12361b6d23f793580a50a6008633501c56ea1d] bcm63xx_enet: delete a redundant assignment
> git bisect good 3e12361b6d23f793580a50a6008633501c56ea1d
> # good: [78d788681492abe4980d5cc9b93b70df9f028880] Merge remote-tracking branch 'jc_docs/docs-next'
> git bisect good 78d788681492abe4980d5cc9b93b70df9f028880
> # good: [266234e7659f731cf471a1bdc4fd1ead4caa8303] Merge remote-tracking branch 'v4l-dvb-next/master'
> git bisect good 266234e7659f731cf471a1bdc4fd1ead4caa8303
> # bad: [be1841fe3ca0010139fe4fb44dd42dea7c0e3401] Merge remote-tracking branch 'swiotlb/linux-next'
> git bisect bad be1841fe3ca0010139fe4fb44dd42dea7c0e3401
> # good: [7b8798617c7975d10678d99dcc59d103e237b4cd] Merge remote-tracking branch 'ieee1394/for-next'
> git bisect good 7b8798617c7975d10678d99dcc59d103e237b4cd
> # good: [463e862ac63ef27fca423782536f6465abc3f180] swiotlb: Convert io_default_tlb_mem to static allocation
> git bisect good 463e862ac63ef27fca423782536f6465abc3f180
> # good: [2dc6b1158c28c3a5e86d162628810312f98d5e97] fs: dlm: introduce generic listen
> git bisect good 2dc6b1158c28c3a5e86d162628810312f98d5e97
> # good: [62699b3f0a62435fceb8debf295e90a5ea259e04] fs: dlm: move receive loop into receive handler
> git bisect good 62699b3f0a62435fceb8debf295e90a5ea259e04
> # bad: [ad6c00283163cb7ad52cdf97d2850547446f7d98] swiotlb: Free tbl memory in swiotlb_exit()
> git bisect bad ad6c00283163cb7ad52cdf97d2850547446f7d98
> # good: [1efd3fc0ccf52e1aa5f0bf5b0d82847180d20951] swiotlb: Emit diagnostic in swiotlb_exit()
> git bisect good 1efd3fc0ccf52e1aa5f0bf5b0d82847180d20951
> # first bad commit: [ad6c00283163cb7ad52cdf97d2850547446f7d98] swiotlb: Free tbl memory in swiotlb_exit()
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