From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:49210) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzPcO-0006Zn-D8 for qemu-devel@nongnu.org; Wed, 17 Jul 2013 07:10:01 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UzPcM-0004O3-Tm for qemu-devel@nongnu.org; Wed, 17 Jul 2013 07:10:00 -0400 Received: from mail-qc0-x22c.google.com ([2607:f8b0:400d:c01::22c]:56953) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzPcM-0004Nz-PW for qemu-devel@nongnu.org; Wed, 17 Jul 2013 07:09:58 -0400 Received: by mail-qc0-f172.google.com with SMTP id j10so1010889qcx.3 for ; Wed, 17 Jul 2013 04:09:58 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <51E67B7A.8000800@redhat.com> Date: Wed, 17 Jul 2013 13:09:46 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1373840171-25556-1-git-send-email-rth@twiddle.net> <1373840171-25556-4-git-send-email-rth@twiddle.net> <8761w9wm50.fsf@blackfin.pond.sub.org> In-Reply-To: <8761w9wm50.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PULL 3/5] exec: Support 64-bit operations in address_space_rw List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: aliguori@us.ibm.com, Gerd Hoffmann , qemu-devel@nongnu.org, Richard Henderson Il 17/07/2013 11:50, Markus Armbruster ha scritto: > Richard Henderson writes: > >> Honor the implementation maximum access size, and at least check >> the minimum access size. >> >> Reviewed-by: Paolo Bonzini >> Signed-off-by: Richard Henderson > > Fails for me: > > qemu-system-x86_64: /work/armbru/qemu/exec.c:1927: memory_access_size: Assertion `l >= access_size_min' failed. This: unsigned access_size_min = mr->ops->impl.min_access_size; unsigned access_size_max = mr->ops->impl.max_access_size; must be respectively: unsigned access_size_min = 1; unsigned access_size_max = mr->ops->valid.max_access_size; access_size_min can be 1 because erroneous accesses must not crash QEMU, they should trigger exceptions in the guest or just return garbage (depending on the CPU). I'm not sure I understand the comment, placing a 4-byte field at the last byte of a region makes no sense (unless impl.unaligned is true). access_size_max can be mr->ops->valid.max_access_size because memory.c can and will still break accesses bigger than mr->ops->impl.max_access_size. Markus, can you try the minimal patch above? Or this one that also does the consequent simplifications. diff --git a/exec.c b/exec.c index c99a883..0904283 100644 --- a/exec.c +++ b/exec.c @@ -1898,14 +1898,8 @@ static inline bool memory_access_is_direct(MemoryRegion *mr, bool is_write) static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr) { - unsigned access_size_min = mr->ops->impl.min_access_size; - unsigned access_size_max = mr->ops->impl.max_access_size; + unsigned access_size_max = mr->ops->valid.max_access_size; - /* Regions are assumed to support 1-4 byte accesses unless - otherwise specified. */ - if (access_size_min == 0) { - access_size_min = 1; - } if (access_size_max == 0) { access_size_max = 4; } @@ -1922,9 +1916,6 @@ static int memory_access_size(MemoryRegion *mr, unsigned l, hwaddr addr) if (l > access_size_max) { l = access_size_max; } - /* ??? The users of this function are wrong, not supporting minimums larger - than the remaining length. C.f. memory.c:access_with_adjusted_size. */ - assert(l >= access_size_min); return l; } Paolo