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Mon, 29 Nov 2021 17:53:18 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4869CB207F; Mon, 29 Nov 2021 17:53:17 +0000 (GMT) Received: from localhost.localdomain (unknown [9.160.7.253]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Mon, 29 Nov 2021 17:53:17 +0000 (GMT) Message-ID: <481725de02c9b37c736ce0f12757c4a21cf12cf1.camel@linux.ibm.com> Subject: [PATCH 08/10] powerpc/vas: Return paste instruction failure if no active window From: Haren Myneni To: mpe@ellerman.id.au, linuxppc-dev@lists.ozlabs.org, npiggin@gmail.com Date: Mon, 29 Nov 2021 09:53:15 -0800 In-Reply-To: References: User-Agent: Evolution 3.36.5 (3.36.5-2.fc32) MIME-Version: 1.0 X-TM-AS-GCONF: 00 X-Proofpoint-GUID: DzoLwVPFG_F86brgq3omqbwa3Y6dD6pD X-Proofpoint-ORIG-GUID: JivT2uNrcstpi754I5VJ8i1fEShrnSjD X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.790,Hydra:6.0.425,FMLib:17.0.607.475 definitions=2021-11-29_10,2021-11-28_01,2020-04-07_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxlogscore=999 lowpriorityscore=0 malwarescore=0 priorityscore=1501 adultscore=0 mlxscore=0 suspectscore=0 impostorscore=0 clxscore=1015 spamscore=0 phishscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2110150000 definitions=main-2111290082 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: , Errors-To: linuxppc-dev-bounces+incoming=patchwork.ozlabs.org@lists.ozlabs.org Sender: "Linuxppc-dev" The VAS window may not be active if the system looses credits and the NX generates page fault when it receives request on unmap paste address. The kernel handles the fault by remap new paste address if the window is active again, Otherwise return the paste instruction failure if the executed instruction that caused the fault was a paste. Signed-off-by: Nicholas Piggin Signed-off-by: Haren Myneni --- arch/powerpc/include/asm/ppc-opcode.h | 2 ++ arch/powerpc/platforms/book3s/vas-api.c | 47 ++++++++++++++++++++++++- 2 files changed, 48 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/include/asm/ppc-opcode.h b/arch/powerpc/include/asm/ppc-opcode.h index baea657bc868..30bb3c0e07f9 100644 --- a/arch/powerpc/include/asm/ppc-opcode.h +++ b/arch/powerpc/include/asm/ppc-opcode.h @@ -261,6 +261,8 @@ #define PPC_INST_MFSPR_PVR 0x7c1f42a6 #define PPC_INST_MFSPR_PVR_MASK 0xfc1ffffe #define PPC_INST_MTMSRD 0x7c000164 +#define PPC_INST_PASTE 0x7c20070d +#define PPC_INST_PASTE_MASK 0xfc2007ff #define PPC_INST_POPCNTB 0x7c0000f4 #define PPC_INST_POPCNTB_MASK 0xfc0007fe #define PPC_INST_RFEBB 0x4c000124 diff --git a/arch/powerpc/platforms/book3s/vas-api.c b/arch/powerpc/platforms/book3s/vas-api.c index 5ceba75c13eb..2ffd34bc4032 100644 --- a/arch/powerpc/platforms/book3s/vas-api.c +++ b/arch/powerpc/platforms/book3s/vas-api.c @@ -351,6 +351,41 @@ static int coproc_release(struct inode *inode, struct file *fp) return 0; } +/* + * If the executed instruction that caused the fault was a paste, then + * clear regs CR0[EQ], advance NIP, and return 0. Else return error code. + */ +static int do_fail_paste(void) +{ + struct pt_regs *regs = current->thread.regs; + u32 instword; + + if (WARN_ON_ONCE(!regs)) + return -EINVAL; + + if (WARN_ON_ONCE(!user_mode(regs))) + return -EINVAL; + + /* + * If we couldn't translate the instruction, the driver should + * return success without handling the fault, it will be retried + * or the instruction fetch will fault. + */ + if (get_user(instword, (u32 __user *)(regs->nip))) + return -EAGAIN; + + /* + * Not a paste instruction, driver may fail the fault. + */ + if ((instword & PPC_INST_PASTE_MASK) != PPC_INST_PASTE) + return -ENOENT; + + regs->ccr &= ~0xe0000000; /* Clear CR0[0-2] to fail paste */ + regs_add_return_ip(regs, 4); /* Skip the paste */ + + return 0; +} + /* * This fault handler is invoked when the VAS/NX generates page fault on * the paste address. Happens if the kernel closes window in hypervisor @@ -403,9 +438,19 @@ static vm_fault_t vas_mmap_fault(struct vm_fault *vmf) } mutex_unlock(&txwin->task_ref.mmap_mutex); - return VM_FAULT_SIGBUS; + /* + * Received this fault due to closing the actual window. + * It can happen during migration or lost credits. + * Since no mapping, return the paste instruction failure + * to the user space. + */ + ret = do_fail_paste(); + if (!ret) + return VM_FAULT_NOPAGE; + return VM_FAULT_SIGBUS; } + static const struct vm_operations_struct vas_vm_ops = { .fault = vas_mmap_fault, };