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Thu, 6 Aug 2026 14:37:42 +0000 (GMT) Date: Thu, 6 Aug 2026 16:37:39 +0200 From: Claudio Imbrenda To: Christian Borntraeger Cc: Janosch Frank , KVM , David Hildenbrand , linux-s390 , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Sven Schnelle Subject: Re: [PATCH 1/1] KVM: s390: Fix memory corruption by not reinjecting CK machine checks Message-ID: <20260806163739.7b1ee8fd@p-imbrenda> In-Reply-To: <20260806125241.210170-2-borntraeger@linux.ibm.com> References: <20260806125241.210170-1-borntraeger@linux.ibm.com> <20260806125241.210170-2-borntraeger@linux.ibm.com> Organization: IBM X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: 3NkEF6gNitnVzz6GOHETFJILwOZxDG7o X-Proofpoint-ORIG-GUID: 3NkEF6gNitnVzz6GOHETFJILwOZxDG7o X-Proofpoint-Spam-Info: AW1haW4tMjYwODA2MDExMiBTYWx0ZWRfX2P0fncNfwljL /3LAYjshJSZqCix9BT+RreStBLCD8H8ud59qK2UeL1w5xSCYMcddX4gn3lPXF6Q5JiVDi1Cn+na XoNQvT0EAtj0bhbHjYPNKpPAGkGkC70= X-Authority-Analysis: v=2.4 cv=K8cS2SWI c=1 sm=1 tr=0 ts=6a749c3b cx=c_pps a=bLidbwmWQ0KltjZqbj+ezA==:117 a=bLidbwmWQ0KltjZqbj+ezA==:17 a=kj9zAlcOel0A:10 a=Sv0fKeRqtYgA:10 a=VkNPw1HP01LnGYTKEx00:22 a=RnoormkPH1_aCDwRdu11:22 a=uAbxVGIbfxUO_5tXvNgY:22 a=VnNF1IyMAAAA:8 a=VwQbUJbxAAAA:8 a=WOMeMtZcLbvEFOhP14wA:9 a=CjuIK1q_8ugA:10 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwODA2MDExMiBTYWx0ZWRfX+AWC4EWvfQX6 0SmXA2yxGGMR+7LK+9wtwG3C/REa6+aXQ1dLB0jGPljzjLgvdJhGIYfoC1zOUFj57+tFoQozd5l r6k1JkIow4DCOGKJpV6GTD0oqI7cuT82E82YqAQ7Yk+zucLDD+bY41Dpzbl2oem2NJJneEwkZpK 6edNdIw7Ry+mkBkvZZ2/BqNNopOU1nYHWV+KRfZiYaFvKOLsvuXFFjBJTuVXb6/e7irgIee8Z5Q 7xlz/9BHkmETucLqyyLn1qBZFSGBQQgJyBZ2kV7FHCFmst40vJ9wPWsF/TpwlPvyKbJj89/W5kd cHcF/TSo1+R+fLG+AWnBs/W4/Mzbg7kEVhHeytJkZG0f2bZ0QIvPATgjUKzOyIpiRrcYEssHC97 er7vK61Si2kXindkuGhGsAThvKBXU62UQHJ+fqJ49Ee8DwEBi44pYzZPhvxRH18ttVYuFosPVlc +2r21xg9n3Daoevi7UA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1176,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-08-05_06,2026-08-05_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 spamscore=0 impostorscore=0 bulkscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 phishscore=0 suspectscore=0 adultscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2608060112 On Thu, 6 Aug 2026 14:52:41 +0200 Christian Borntraeger wrote: > Channel-subsystem damage machine checks are for the host channel > subsystem. The guest channel subsystem is emulated in the userspace VMM. > There is no point in forwarding such machine checks into the guest. > > This also simplifies the machine check reinjection and avoids kfree of a > stack variable as reported by sashiko. There might be still machine > checks that have the ck bit set with another bit (like instruction > damage), mask out the CK bit in s390_backup_mcck_info(), like the CP and > ED bits already are. > > Fixes: 4d62fcc0b692 ("KVM: s390: Inject machine check into the guest") > Cc: stable@vger.kernel.org > Signed-off-by: Christian Borntraeger > --- > arch/s390/include/asm/nmi.h | 1 + > arch/s390/kernel/nmi.c | 4 ++-- > arch/s390/kvm/interrupt.c | 24 ++++++++---------------- > 3 files changed, 11 insertions(+), 18 deletions(-) > > diff --git a/arch/s390/include/asm/nmi.h b/arch/s390/include/asm/nmi.h > index 6454c1531854..dd26c20bd231 100644 > --- a/arch/s390/include/asm/nmi.h > +++ b/arch/s390/include/asm/nmi.h > @@ -22,6 +22,7 @@ > #define MCCK_CODE_SYSTEM_DAMAGE BIT(63) > #define MCCK_CODE_EXT_DAMAGE BIT(63 - 5) > #define MCCK_CODE_CP BIT(63 - 9) > +#define MCCK_CODE_CK BIT(63 - 11) > #define MCCK_CODE_STG_ERROR BIT(63 - 16) > #define MCCK_CODE_STG_KEY_ERROR BIT(63 - 18) > #define MCCK_CODE_STG_DEGRAD BIT(63 - 19) > diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c > index e17a59d4d5a4..652b98795243 100644 > --- a/arch/s390/kernel/nmi.c > +++ b/arch/s390/kernel/nmi.c > @@ -345,7 +345,7 @@ static void notrace s390_backup_mcck_info(struct pt_regs *regs) > sie_page = container_of(sie_block, struct sie_page, sie_block); > mcck_backup = &sie_page->mcck_info; > mcck_backup->mcic = get_lowcore()->mcck_interruption_code & > - ~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE); > + ~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE | MCCK_CODE_CK); ... here, instead of duplicating it? > mcck_backup->ext_damage_code = get_lowcore()->external_damage_code; > mcck_backup->failing_storage_address = get_lowcore()->failing_storage_address; > } > @@ -357,7 +357,7 @@ NOKPROBE_SYMBOL(s390_backup_mcck_info); > #define ED_STP_ISLAND 6 /* External damage STP island check */ > #define ED_STP_SYNC 7 /* External damage STP sync check */ > > -#define MCCK_CODE_NO_GUEST (MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE) > +#define MCCK_CODE_NO_GUEST (MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE | MCCK_CODE_CK) it looks like this macro here should have been used above... ^ > > /* > * machine check handler. 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