From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55652) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eH9pZ-0001nR-6Z for qemu-devel@nongnu.org; Tue, 21 Nov 2017 09:47:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eH9pT-0001Hl-0r for qemu-devel@nongnu.org; Tue, 21 Nov 2017 09:47:21 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36252) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eH9pS-0001HQ-Nb for qemu-devel@nongnu.org; Tue, 21 Nov 2017 09:47:14 -0500 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id D035161D20 for ; Tue, 21 Nov 2017 14:47:13 +0000 (UTC) Date: Tue, 21 Nov 2017 16:47:11 +0200 From: "Michael S. Tsirkin" Message-ID: <20171121164254-mutt-send-email-mst@kernel.org> References: <1510834622-28800-1-git-send-email-thuth@redhat.com> <20171120175522.76bf71c3@redhat.com> <20171120223048-mutt-send-email-mst@kernel.org> <20171121142639.3e6d2e79@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171121142639.3e6d2e79@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2] tests/bios-tables-test: Fix endianess problems when passing data to iasl List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: Thomas Huth , qemu-devel@nongnu.org On Tue, Nov 21, 2017 at 02:26:39PM +0100, Igor Mammedov wrote: > On Mon, 20 Nov 2017 22:32:29 +0200 > "Michael S. Tsirkin" wrote: > > > On Mon, Nov 20, 2017 at 05:55:22PM +0100, Igor Mammedov wrote: > > > On Thu, 16 Nov 2017 13:17:02 +0100 > > > Thomas Huth wrote: > > > > > > > The bios-tables-test was writing out files that we pass to iasl in > > > > with the wrong endianness in the header when running on a big endian > > > > host. So instead of storing mixed endian information in our structures, > > > > let's keep everything in little endian and byte-swap it only when we > > > > need a value in the code. > > > > > > > > Reported-by: Daniel P. Berrange > > > > Buglink: https://bugs.launchpad.net/qemu/+bug/1724570 > > > > Suggested-by: Michael S. Tsirkin > > > > Signed-off-by: Thomas Huth > > > > --- > > > > v2: Fixed vmgenid-test which was accidentially broken in v1 > > > > > > > > tests/acpi-utils.h | 27 +++++---------------------- > > > > tests/bios-tables-test.c | 42 ++++++++++++++++++++++-------------------- > > > > tests/vmgenid-test.c | 22 ++++++++++++---------- > > > > 3 files changed, 39 insertions(+), 52 deletions(-) > > > > > > > > diff --git a/tests/acpi-utils.h b/tests/acpi-utils.h > > > > index f8d8723..d5ca5b6 100644 > > > > --- a/tests/acpi-utils.h > > > > +++ b/tests/acpi-utils.h > > > > @@ -28,24 +28,9 @@ typedef struct { > > > > bool tmp_files_retain; /* do not delete the temp asl/aml */ > > > > } AcpiSdtTable; > > > > > > > > -#define ACPI_READ_FIELD(field, addr) \ > > > > - do { \ > > > > - switch (sizeof(field)) { \ > > > > - case 1: \ > > > > - field = readb(addr); \ > > > > - break; \ > > > > - case 2: \ > > > > - field = readw(addr); \ > > > > - break; \ > > > > - case 4: \ > > > > - field = readl(addr); \ > > > > - break; \ > > > > - case 8: \ > > > > - field = readq(addr); \ > > > > - break; \ > > > > - default: \ > > > > - g_assert(false); \ > > > > - } \ > > > probably it's been discussed but, why not do > > > leXX_to_cpu() > > > here, instead of making each place that access read field > > > to do leXX_to_cpu() manually.? > > > > > > Beside of keeping access to structure in natural host order, > > > it should also be less error-prone as field users don't > > > have to worry about endianness. > > > > Yes, I suggested that. > > The issue is that we don't byte-swap all of the tables > > (we can't, that would require a full ACPI parser). > > So when byte-swapping we end up with a mixed host/LE > > structures. > Agreed that having mixed endianness structures is hard to deal with. > Unfortunately switching away from host endianness for some structures > doesn't make code less confused as we still have mixed > structures in use (internal vs acpi ones). We can't change ACPI so internal ones should switch to LE for consistency IMHO. If a specific field is accessed a lot, we can add an API that does a byte swap internally. > > That's why I'd rather make ACPI_FOO accessors take in/return data > in host byte order so that test case won't have to worry about it > as far as LE blobs are accessed via ACPI_FOO(). It'd be a lot less > fragile. What we really need to do is support __attribute__((bitwise)) from sparse. Then we can have endian-ness statically checked. > What tables/use-cases do you have in mind where we'd need full > ACPI parser /whatever it is/? We dump ACPI tables for parsing by iasl. > > > Keeping it all LE seems cleaner. > > > >