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Thu, 02 Apr 2020 07:20:27 +0000 Received: from b01ledav006.gho.pok.ibm.com (b01ledav006.gho.pok.ibm.com [9.57.199.111]) by b01cxnp22035.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id 0327KR3l53346634 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 2 Apr 2020 07:20:27 GMT Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 0A313AC05B; Thu, 2 Apr 2020 07:20:27 +0000 (GMT) Received: from b01ledav006.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id DD95AAC05E; Thu, 2 Apr 2020 07:20:25 +0000 (GMT) Received: from [9.70.82.143] (unknown [9.70.82.143]) by b01ledav006.gho.pok.ibm.com (Postfix) with ESMTP; Thu, 2 Apr 2020 07:20:25 +0000 (GMT) Subject: [PATCH v10 14/14] powerpc: Use mm_context vas_windows counter to issue CP_ABORT From: Haren Myneni To: mpe@ellerman.id.au In-Reply-To: <1585810846.2275.23.camel@hbabu-laptop> References: <1585810846.2275.23.camel@hbabu-laptop> Content-Type: text/plain; charset="UTF-8" Date: Thu, 02 Apr 2020 00:20:24 -0700 Message-ID: <1585812024.2275.68.camel@hbabu-laptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.138, 18.0.676 definitions=2020-04-01_04:2020-03-31, 2020-04-01 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 lowpriorityscore=0 mlxlogscore=999 clxscore=1015 bulkscore=0 malwarescore=0 suspectscore=1 phishscore=0 priorityscore=1501 spamscore=0 adultscore=0 impostorscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2003020000 definitions=main-2004020063 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mikey@neuling.org, ajd@linux.ibm.com, frederic.barrat@fr.ibm.com, linux-kernel@vger.kernel.org, npiggin@gmail.com, hch@infradead.org, oohall@gmail.com, clg@kaod.org, herbert@gondor.apana.org.au, sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, srikar@linux.vnet.ibm.com Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" set_thread_uses_vas() sets used_vas flag for a process that opened VAS window and issue CP_ABORT during context switch for only that process. In multi-thread application, windows can be shared. For example Thread A can open a window and Thread B can run COPY/PASTE instructions to send NX request which may cause corruption or snooping or a covert channel. Also once this flag is set, continue to run CP_ABORT even the VAS window is closed. So define vas-windows counter in process mm_context, increment this counter for each window open and decrement it for window close. If vas-windows is set, issue CP_ABORT during context switch. It means clear the foreign real address mapping only if the process / thread uses COPY/PASTE. Then disable it for that process if windows are not open. Signed-off-by: Haren Myneni Reported-by: Nicholas Piggin Suggested-by: Milton Miller Suggested-by: Nicholas Piggin --- arch/powerpc/include/asm/book3s/64/mmu.h | 3 +++ arch/powerpc/include/asm/mmu_context.h | 22 ++++++++++++++++++++++ arch/powerpc/include/asm/processor.h | 1 - arch/powerpc/kernel/process.c | 8 ++++++-- arch/powerpc/platforms/powernv/vas-window.c | 1 + 5 files changed, 32 insertions(+), 3 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/mmu.h b/arch/powerpc/include/asm/book3s/64/mmu.h index bb3deb7..f0a9ff6 100644 --- a/arch/powerpc/include/asm/book3s/64/mmu.h +++ b/arch/powerpc/include/asm/book3s/64/mmu.h @@ -116,6 +116,9 @@ struct patb_entry { /* Number of users of the external (Nest) MMU */ atomic_t copros; + /* Number of user space windows opened in process mm_context */ + atomic_t vas_windows; + struct hash_mm_context *hash_context; unsigned long vdso_base; diff --git a/arch/powerpc/include/asm/mmu_context.h b/arch/powerpc/include/asm/mmu_context.h index 360367c..7fd249498 100644 --- a/arch/powerpc/include/asm/mmu_context.h +++ b/arch/powerpc/include/asm/mmu_context.h @@ -185,11 +185,33 @@ static inline void mm_context_remove_copro(struct mm_struct *mm) dec_mm_active_cpus(mm); } } + +/* + * vas_windows counter shows number of open windows in the mm + * context. During context switch, use this counter to clear the + * foreign real address mapping (CP_ABORT) for the thread / process + * that intend to use COPY/PASTE. When a process closes all windows, + * disable CP_ABORT which is expensive to run. + */ +static inline void mm_context_add_vas_windows(struct mm_struct *mm) +{ + atomic_inc(&mm->context.vas_windows); +} + +static inline void mm_context_remove_vas_windows(struct mm_struct *mm) +{ + int c = atomic_dec_if_positive(&mm->context.vas_windows); + + /* Detect imbalance between add and remove */ + WARN_ON(c < 0); +} #else static inline void inc_mm_active_cpus(struct mm_struct *mm) { } static inline void dec_mm_active_cpus(struct mm_struct *mm) { } static inline void mm_context_add_copro(struct mm_struct *mm) { } static inline void mm_context_remove_copro(struct mm_struct *mm) { } +static inline void mm_context_add_vas_windows(struct mm_struct *mm) { } +static inline void mm_context_remove_vas_windows(struct mm_struct *mm) { } #endif diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index eedcbfb..bfa336f 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -272,7 +272,6 @@ struct thread_struct { unsigned mmcr0; unsigned used_ebb; - unsigned int used_vas; #endif }; diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index fad50db..a3ecaf9 100644 --- a/arch/powerpc/kernel/process.c +++ b/arch/powerpc/kernel/process.c @@ -1221,7 +1221,8 @@ struct task_struct *__switch_to(struct task_struct *prev, * mappings, we must issue a cp_abort to clear any state and * prevent snooping, corruption or a covert channel. */ - if (current->thread.used_vas) + if (current->mm && + atomic_read(¤t->mm->context.vas_windows)) asm volatile(PPC_CP_ABORT); } #endif /* CONFIG_PPC_BOOK3S_64 */ @@ -1466,7 +1467,10 @@ int set_thread_uses_vas(void) if (!cpu_has_feature(CPU_FTR_ARCH_300)) return -EINVAL; - current->thread.used_vas = 1; + if (!current->mm) + return -EINVAL; + + mm_context_add_vas_windows(current->mm); /* * Even a process that has no foreign real address mapping can use diff --git a/arch/powerpc/platforms/powernv/vas-window.c b/arch/powerpc/platforms/powernv/vas-window.c index 3ffad5a..33dfbbf 100644 --- a/arch/powerpc/platforms/powernv/vas-window.c +++ b/arch/powerpc/platforms/powernv/vas-window.c @@ -1333,6 +1333,7 @@ int vas_win_close(struct vas_window *window) put_pid(window->pid); if (window->mm) { mm_context_remove_copro(window->mm); + mm_context_remove_vas_windows(window->mm); mmdrop(window->mm); } } -- 1.8.3.1