From: Paolo Bonzini <pbonzini@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>,
Peter Zijlstra <peterz@infradead.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
viro@zeniv.linux.org.uk, schwidefsky@de.ibm.com,
rientjes@google.com, riel@redhat.com, mingo@kernel.org,
mgorman@suse.de,
kirill shutemov <kirill.shutemov@linux.intel.com>,
heiko carstens <heiko.carstens@de.ibm.com>,
hannes@cmpxchg.org, gerald schaefer <gerald.schaefer@de.ibm.com>,
ebiederm@xmission.com, aarcange@redhat.com
Subject: Re: + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree
Date: Wed, 26 Feb 2014 15:41:32 -0500 (EST) [thread overview]
Message-ID: <842178473.10219645.1393447292444.JavaMail.zimbra@redhat.com> (raw)
In-Reply-To: <20140226180603.GA25644@redhat.com>
> +#ifdef CONFIG_S390
> + /*
> + * MADV_HUGEPAGE is broken after s390_enable_sie(), qemu
> + * blindly does madvise(MADV_HUGEPAGE) for for all kvm pages
> + * and expects it must fail on s390. Avoid a possible SIGSEGV
> + * until qemu is changed.
> + */
> + if (mm_has_pgste(vma->vm_mm))
> + return -EINVAL;
> +#endif
The comment is not quite true. QEMU doesn't expect that the madvise fails.
It simply expects that the madvise doesn't cause SIGSEGVs or later
malfunctioning, because (quoting tha man page) madvise "does not influence
the semantics of the application".
There's nothing to fix in QEMU, in fact I believe this should return 0
rather than -EINVAL. It's perfectly legal for the kernel to ignore an madvise,
and this is what should happen here.
Paolo
next prev parent reply other threads:[~2014-02-26 20:42 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <530d2ce9.eikv0ULecNwxF4I5%akpm@linux-foundation.org>
[not found] ` <530D9F50.1080400@de.ibm.com>
2014-02-26 14:50 ` + mm-revert-thp-make-madv_hugepage-check-for-mm-def_flags.patch added to -mm tree Oleg Nesterov
2014-02-26 15:06 ` Christian Borntraeger
2014-02-26 15:22 ` Kirill A. Shutemov
2014-02-26 15:31 ` Oleg Nesterov
2014-02-26 16:55 ` Gerald Schaefer
2014-02-26 16:57 ` Peter Zijlstra
2014-02-26 17:22 ` Alex Thorlton
2014-02-26 18:06 ` Oleg Nesterov
2014-02-26 19:05 ` Gerald Schaefer
2014-02-27 16:45 ` Oleg Nesterov
2014-02-26 19:27 ` Christian Borntraeger
2014-02-26 19:39 ` Alex Thorlton
2014-02-26 23:24 ` Andrew Morton
2014-02-27 0:01 ` Alex Thorlton
2014-02-27 17:26 ` Alex Thorlton
2014-02-26 20:41 ` Paolo Bonzini [this message]
2014-02-27 16:34 ` Oleg Nesterov
2014-02-26 18:08 ` Oleg Nesterov
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