From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:39763) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bxZC3-0003G3-U3 for qemu-devel@nongnu.org; Fri, 21 Oct 2016 08:45:04 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bxZBz-0005kp-UR for qemu-devel@nongnu.org; Fri, 21 Oct 2016 08:45:03 -0400 Received: from mx1.redhat.com ([209.132.183.28]:49048) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1bxZBz-0005kj-Mk for qemu-devel@nongnu.org; Fri, 21 Oct 2016 08:44:59 -0400 Date: Fri, 21 Oct 2016 14:44:54 +0200 From: Igor Mammedov Message-ID: <20161021144454.381fd7cd@nial.brq.redhat.com> In-Reply-To: <695474a1-1a40-8b1d-42bb-013e7d4119a4@intel.com> References: <20161021082801.dglwfsocljohquok@hz-desktop> <695474a1-1a40-8b1d-42bb-013e7d4119a4@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] Regression caused by d2f39ad "exec.c: Ensure right alignment also for file backed ram" List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Haozhong Zhang Cc: qemu-devel@nongnu.org, chao.p.peng@intel.com, Eduardo Habkost , Peter Crosthwaite , Dominik Dingel , anthony.xu@intel.com, Paolo Bonzini , Richard Henderson , Xiao Guangrong On Fri, 21 Oct 2016 16:39:08 +0800 Haozhong Zhang wrote: > On 10/21/2016 04:28 PM, Haozhong Zhang wrote: > > Hi, > > > > Commit d2f39ad "exec.c: Ensure right alignment also for file backed > > ram" added an additional alignment requirement besides to the previous > > page size for the size of the backend file. On x86, the alignment > > requirement for the size of the backend file is changed from 4KB in > > QEMU 2.6 to 2MB in QEMU 2.7. > > > > This change immediately breaks the usage of "-object > > memory-backend-file,...,size=$SIZE" > > I forgot the frontend part, the broken usage should be > -object memory-backend-file,id=mem1,mem-path=$FILE,size=$SIZE > -device nvdimm,id=nv1,memdev=mem1 > where $SIZE is multiple of 4KB but not 2MB. > > It works on QEMU 2.6, but fails on 2.7 when pc_dimm_memory_plug() tries > to plug the nvdimm device. it affect's not only nvdimm but also pc-dimm, qemu -m 1G,slots=10,maxmem=10G \ -object memory-backend-file,id=mem1,mem-path=/tmp,size=0x3e2000 -device pc-dimm,memdev=mem1 qemu: -device pc-dimm,memdev=mem1: backend memory size must be multiple of 0x200000 As for nvdimms d2f39ad commit changes auto-generated GPA when 'addr' property is not provided pre bug: mhp_pc_dimm_assigned_address 0x100000000 mhp_pc_dimm_assigned_slot 0x0 mhp_pc_dimm_assigned_address 0x1003e2000 mhp_pc_dimm_assigned_slot 0x1 vs post bug: mhp_pc_dimm_assigned_address 0x100000000 mhp_pc_dimm_assigned_slot 0 mhp_pc_dimm_assigned_address 0x100200000 mhp_pc_dimm_assigned_slot 1 or if 'addr' is provided, qemu will fail with "address must be aligned to 0x200000 bytes" so migration from qemu-2.6 and older builds to 2.7 and later isn't possible due to inability to start target with 2.6-page_based alignment. > > Haozhong > > > on x86, where $SIZE is multiple of 4KB but not 2MB. It works on QEMU 2.6. > > Could this be considered as a regression? > > > > The commit message shows it's for s390. I'm wondering whether the same > > regression happens on s390 and ARM. If not, could I fix the regression > > on x86 by keeping using the original alignment only on x86, e.g. > > > > modified exec.c > > @@ -1254,7 +1254,11 @@ static void *file_ram_alloc(RAMBlock *block, > > } > > > > block->page_size = qemu_fd_getpagesize(fd); > > +#if defined(__x86_64__) || defined(__i386__) > > + block->mr->align = block->page_size; > > +#else > > block->mr->align = MAX(block->page_size, QEMU_VMALLOC_ALIGN); > > +#endif > > > > if (memory < block->page_size) { > > error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal > > to " > > > > > > Thanks, > > Haozhong > > >