From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59992) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzVbJ-0004bt-7X for qemu-devel@nongnu.org; Wed, 17 Jul 2013 13:33:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1UzVbG-00068C-QL for qemu-devel@nongnu.org; Wed, 17 Jul 2013 13:33:17 -0400 Received: from mx1.redhat.com ([209.132.183.28]:63875) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1UzVbG-00067t-Je for qemu-devel@nongnu.org; Wed, 17 Jul 2013 13:33:14 -0400 Message-ID: <51E6D54B.7020700@redhat.com> Date: Wed, 17 Jul 2013 19:32:59 +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> <51E67B7A.8000800@redhat.com> <8761w9gp88.fsf@codemonkey.ws> In-Reply-To: <8761w9gp88.fsf@codemonkey.ws> 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: Anthony Liguori Cc: qemu-devel@nongnu.org, Gerd Hoffmann , Markus Armbruster , Richard Henderson Il 17/07/2013 17:50, Anthony Liguori ha scritto: > Paolo Bonzini writes: > >> 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. > > FYI, the reproducer is very simple: > > qemu-system-x86_64 -usb My patch works. Paolo > Regards, > > Anthony Liguori > >> >> 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 >