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Rao" , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , , , , , , , Guohanjun References: <20240129134652.4004931-1-tongtiangen@huawei.com> <20240129134652.4004931-3-tongtiangen@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600017.china.huawei.com (7.193.23.234) X-Rspamd-Queue-Id: 7FFDF40013 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: ipem1stkd13t4shgg96yn93e58sydsn5 X-HE-Tag: 1706620987-359901 X-HE-Meta: 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 407ZW/8j QnWhdOZbWjckaaU7jjXW8UxJUI+5diGRbhDqeHuPLA5BXOajYKwo/H2NYbf04M5SoFaWc9XjHBOfr8mgx1jpuEbqAvAG+2R+g+PKKfIv0eKjU6rCEuLDxpoQnxt/eZOQVeMUPvoHEw8CgzpG/Kt9sGWQS842aXb/H9+r2KA+afW1eCRC/wHFI6kmm9lpspadbZ11duvWFKznO7JUHE+/4cFCNtiBNqHfqUM3v2rnM6nK9p3s= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 在 2024/1/30 21:07, Mark Rutland 写道: > On Tue, Jan 30, 2024 at 06:57:24PM +0800, Tong Tiangen wrote: >> 在 2024/1/30 1:51, Mark Rutland 写道: >>> On Mon, Jan 29, 2024 at 09:46:48PM +0800, Tong Tiangen wrote: > >>>> diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c >>>> index 55f6455a8284..312932dc100b 100644 >>>> --- a/arch/arm64/mm/fault.c >>>> +++ b/arch/arm64/mm/fault.c >>>> @@ -730,6 +730,31 @@ static int do_bad(unsigned long far, unsigned long esr, struct pt_regs *regs) >>>> return 1; /* "fault" */ >>>> } >>>> +static bool arm64_do_kernel_sea(unsigned long addr, unsigned int esr, >>>> + struct pt_regs *regs, int sig, int code) >>>> +{ >>>> + if (!IS_ENABLED(CONFIG_ARCH_HAS_COPY_MC)) >>>> + return false; >>>> + >>>> + if (user_mode(regs)) >>>> + return false; >>> >>> This function is called "arm64_do_kernel_sea"; surely the caller should *never* >>> call this for a SEA taken from user mode? >> >> In do_sea(), the processing logic is as follows: >> do_sea() >> { >> [...] >> if (user_mode(regs) && apei_claim_sea(regs) == 0) { >> return 0; >> } >> [...] >> //[1] >> if (!arm64_do_kernel_sea()) { >> arm64_notify_die(); >> } >> } >> >> [1] user_mode() is still possible to go here,If user_mode() goes here, >> it indicates that the impact caused by the memory error cannot be >> processed correctly by apei_claim_sea(). >> >> >> In this case, only arm64_notify_die() can be used, This also maintains >> the original logic of user_mode()'s processing. > > My point is that either: > > (a) The name means that this should *only* be called for SEAs from a kernel > context, and the caller should be responsible for ensuring that. > > (b) The name is misleading, and the 'kernel' part should be removed from the > name. > > I prefer (a), and if you head down that route it's clear that you can get rid > of a bunch of redundant logic and remove the need for do_kernel_sea(), anyway, > e.g. > > | static int do_sea(unsigned long far, unsigned long esr, struct pt_regs *regs) > | { > | const struct fault_info *inf = esr_to_fault_info(esr); > | bool claimed = apei_claim_sea(regs) == 0; > | unsigned long siaddr; > | > | if (claimed) { > | if (user_mode(regs)) { > | /* > | * APEI claimed this as a firmware-first notification. > | * Some processing deferred to task_work before ret_to_user(). > | */ > | return 0; > | } else { > | /* > | * TODO: explain why this is correct. > | */ > | if ((current->flags & PF_KTHREAD) && > | fixup_exception_mc(regs)) > | return 0; > | } > | } This code seems to be a bit more concise and avoids misleading function names, which I'll use in the next version:） > | > | if (esr & ESR_ELx_FnV) { > | siaddr = 0; > | } else { > | /* > | * The architecture specifies that the tag bits of FAR_EL1 are > | * UNKNOWN for synchronous external aborts. Mask them out now > | * so that userspace doesn't see them. > | */ > | siaddr = untagged_addr(far); > | } > | arm64_notify_die(inf->name, regs, inf->sig, inf->code, siaddr, esr); > | > | return 0; > | } > >>>> + >>>> + if (apei_claim_sea(regs) < 0) >>>> + return false; >>>> + >>>> + if (!fixup_exception_mc(regs)) >>>> + return false; >>>> + >>>> + if (current->flags & PF_KTHREAD) >>>> + return true; >>> >>> I think this needs a comment; why do we allow kthreads to go on, yet kill user >>> threads? What about helper threads (e.g. for io_uring)? >> >> If a memroy error occurs in the kernel thread, the problem is more >> serious than that of the user thread. As a result, related kernel >> functions, such as khugepaged, cannot run properly. kernel panic should >> be a better choice at this time. >> >> Therefore, the processing scope of this framework is limited to the user >> thread. > > That's reasonable, but needs to be explained in a comment. > > Also, as above, I think you haven't conisderd helper threads (e.g. io_uring), > which don't have PF_KTHREAD set but do have PF_USER_WORKER set. I suspect those > need the same treatment as kthreads. Okay, I'm going to investigate PF_USER_WORKER. > >>>> + set_thread_esr(0, esr); >>> >>> Why do we set the ESR to 0? >> >> The purpose is to reuse the logic of arm64_notify_die() and set the >> following parameters before sending signals to users: >> current->thread.fault_address = 0; >> current->thread.fault_code = err; > > Ok, but there's no need to open-code that. > > As per my above example, please continue to use the existing call to > arm64_notify_die() rather than open-coding bits of it. OK. Many thanks. Tong. > > Mark. > .