From: Dave Hansen <dave.hansen@linux.intel.com>
To: Sean Christopherson <sean.j.christopherson@intel.com>,
linux-kernel@vger.kernel.org
Cc: peterz@infradead.org, tglx@linutronix.de, x86@kernel.org,
luto@kernel.org
Subject: Re: [RFC][PATCH 5/8] x86/mm: fix exception table comments
Date: Fri, 7 Sep 2018 14:51:02 -0700 [thread overview]
Message-ID: <bc50acea-ebc9-5be8-0fcc-9b96031a7348@linux.intel.com> (raw)
In-Reply-To: <1536354280.11460.28.camel@intel.com>
>> + * Only do the expensive exception table search when we might be at
>> + * risk of a deadlock:
>> + * 1. We failed to acquire mmap_sem, and
>> + * 2. The access was an explicit kernel-mode access
>> + * (X86_PF_USER=0).
>
> Might be worth reminding the reader that X86_PF_USER will be set in
> sw_error_code for implicit accesses. I saw "explicit" and my mind
> immediately jumped to hw_error_code for whatever reason. E.g.:
>
> * 2. The access was an explicit kernel-mode access (we set X86_PF_USER
> * in sw_error_code for implicit kernel-mode accesses).
Yeah, that was not worded well. Is this better?
> * Only do the expensive exception table search when we might be at
> * risk of a deadlock:
> * 1. We failed to acquire mmap_sem, and
> * 2. The access was an explicit kernel-mode access. An access
> * from user-mode will X86_PF_USER=1 set via hw_error_code or
> * set in sw_error_code if it were an implicit kernel-mode
> * access that originated in user mode.
next prev parent reply other threads:[~2018-09-07 21:51 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-07 19:48 [RFC][PATCH 0/8] x86/mm: page fault handling cleanups Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 1/8] x86/mm: clarify hardware vs. software "error_code" Dave Hansen
2018-09-07 22:48 ` Andy Lutomirski
2018-09-10 20:07 ` Dave Hansen
2018-09-10 21:17 ` Andy Lutomirski
2018-09-07 19:48 ` [RFC][PATCH 2/8] x86/mm: break out kernel address space handling Dave Hansen
2018-09-07 21:06 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen
2018-09-07 22:21 ` Andy Lutomirski
2018-09-07 22:37 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 3/8] x86/mm: break out user " Dave Hansen
2018-09-08 9:38 ` Peter Zijlstra
2018-09-10 20:20 ` Dave Hansen
2018-09-07 19:48 ` [RFC][PATCH 4/8] x86/mm: add clarifying comments for user addr space Dave Hansen
2018-09-07 19:49 ` [RFC][PATCH 5/8] x86/mm: fix exception table comments Dave Hansen
2018-09-07 21:04 ` Sean Christopherson
2018-09-07 21:51 ` Dave Hansen [this message]
2018-09-10 20:43 ` Sean Christopherson
2018-09-08 0:37 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 6/8] x86/mm: add vsyscall address helper Dave Hansen
2018-09-08 0:46 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 7/8] x86/mm/vsyscall: consider vsyscall page part of user address space Dave Hansen
2018-09-07 22:58 ` Andy Lutomirski
2018-09-08 1:16 ` Jann Horn
2018-09-07 19:49 ` [RFC][PATCH 8/8] x86/mm: remove spurious fault pkey check Dave Hansen
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