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[80.230.85.71]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-46059346676sm8291609f8f.26.2026.06.09.23.58.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Jun 2026 23:58:09 -0700 (PDT) Date: Wed, 10 Jun 2026 02:58:07 -0400 From: "Michael S. Tsirkin" To: Arnd Bergmann Cc: Arnd Bergmann , Jason Wang , Xie Yongji , Eugenio =?iso-8859-1?Q?P=E9rez?= , Xuan Zhuo , Marco Crivellari , Anders Roxell , virtualization@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH] [v3] vduse: fix compat handling for VDUSE_IOTLB_GET_FD/VDUSE_VQ_GET_INFO Message-ID: <20260610025755-mutt-send-email-mst@kernel.org> References: <20260213154051.4172275-1-arnd@kernel.org> <20260610012421-mutt-send-email-mst@kernel.org> <0134edd1-de51-46b3-9ea8-bdbcf48b878f@app.fastmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0134edd1-de51-46b3-9ea8-bdbcf48b878f@app.fastmail.com> On Wed, Jun 10, 2026 at 08:54:59AM +0200, Arnd Bergmann wrote: > On Wed, Jun 10, 2026, at 07:26, Michael S. Tsirkin wrote: > > On Fri, Feb 13, 2026 at 04:40:46PM +0100, Arnd Bergmann wrote: > >> + }; > >> + __u8 ready; > >> + __u8 padding[3]; > >> +} __uapi_arch_align; > > > > what is this __uapi_arch_align supposed to be doing? > > > > It compiles by luck because gcc thinks it's a global variable. > > Sorry, that should not have been part of this patch, it is > part of the series of changes I was testing when I noticed > the problem here, but that other series is unfortunately > still not ready for merging. > > The background here is that I'm adding -Werror=padded to > the UAPI checks in usr/include/Makefile, in order to find > any instances of data structures with implied padding, > and then instead add explicit padding using architecture > specific macros. In vduse_vq_info, this includes a final > 32 bit of padding on architectures with naturally > aligned __u64 but no padding when __u64 has a smaller > alignment. > > The __uapi_arch_align macro in turn is what I add to > structures with optional padding, in order to be able > to reduce the alignment of a structure when building the > kernel with a higher default alignment than userspace > (e.g. on m68k with -malign-int). > > Removing the __uapi_arch_align is the correct fix for the > moment. Let me know if you would like me to send a > replacement patch without it, a fixup patch on top, or if > you will fix it up yourself. > > Arnd I fixed it, thanks.