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(2001-1c00-0c32-7800-5bfa-a036-83f0-f9ec.cable.dynamic.v6.ziggo.nl. [2001:1c00:c32:7800:5bfa:a036:83f0:f9ec]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a8d25d40e8csm633247166b.196.2024.09.11.09.44.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 11 Sep 2024 09:44:44 -0700 (PDT) Message-ID: <8af6253d-83aa-403a-a383-8fb5f5ee0d78@redhat.com> Date: Wed, 11 Sep 2024 18:44:43 +0200 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH hotfix 6.11] minmax: reduce egregious min/max macro expansion To: Lorenzo Stoakes Cc: Andrew Morton , Richard Narron , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Mauro Carvalho Chehab , Sakari Ailus , Greg Kroah-Hartman , Marcin Wojtas , Russell King , "David S . Miller" , Arnd Bergmann , Linus Torvalds , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-media@vger.kernel.org, linux-staging@lists.linux.dev, linux-mm@kvack.org, stable@vger.kernel.org References: <20240911153457.1005227-1-lorenzo.stoakes@oracle.com> <181dec64-5906-4cdd-bb29-40bc7c02d63e@redhat.com> <3f622e05-9843-4763-9191-c980feb831d2@lucifer.local> Content-Language: en-US, nl From: Hans de Goede In-Reply-To: <3f622e05-9843-4763-9191-c980feb831d2@lucifer.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi, On 9/11/24 6:37 PM, Lorenzo Stoakes wrote: > On Wed, Sep 11, 2024 at 06:24:54PM GMT, Hans de Goede wrote: >> Hi Lorenzo, >> >> On 9/11/24 5:34 PM, Lorenzo Stoakes wrote: >>> Avoid nested min()/max() which results in egregious macro expansion. >>> >>> This issue was introduced by commit 867046cc7027 ("minmax: relax check to >>> allow comparison between unsigned arguments and signed constants") [2]. >>> >>> Work has been done to address the issue of egregious min()/max() macro >>> expansion in commit 22f546873149 ("minmax: improve macro expansion and type >>> checking") and related, however it appears that some issues remain on more >>> tightly constrained systems. >>> >>> Adjust a few known-bad cases of deeply nested macros to avoid doing so to >>> mitigate this. Porting the patch first proposed in [1] to Linus's tree. >>> >>> Running an allmodconfig build using the methodology described in [2] we >>> observe a 35 MiB reduction in generated code. >>> >>> The difference is much more significant prior to recent minmax fixes which >>> were not backported. As per [1] prior these the reduction is more like 200 >>> MiB. >>> >>> This resolves an issue with slackware 15.0 32-bit compilation as reported >>> by Richard Narron. >>> >>> Presumably the min/max fixups would be difficult to backport, this patch >>> should be easier and fix's Richard's problem in 5.15. >>> >>> [0]:https://lore.kernel.org/all/b97faef60ad24922b530241c5d7c933c@AcuMS.aculab.com/ >>> [1]:https://lore.kernel.org/lkml/5882b96e-1287-4390-8174-3316d39038ef@lucifer.local/ >>> [2]:https://lore.kernel.org/linux-mm/36aa2cad-1db1-4abf-8dd2-fb20484aabc3@lucifer.local/ >>> >>> Reported-by: Richard Narron >>> Closes: https://lore.kernel.org/all/4a5321bd-b1f-1832-f0c-cea8694dc5aa@aaazen.com/ >>> Fixes: 867046cc7027 ("minmax: relax check to allow comparison between unsigned arguments and signed constants") >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Lorenzo Stoakes >> >> Thank you for your patch. >> >> I must say that I'm not a fan of that this is patching 3 totally >> unrelated files here in a single patch. >> >> This is e.g. going to be a problem if we need to revert one of >> the changes because of regressions... >> >> So I would prefer this to be split into 3 patches. > > Well, I was doing this as a favour to Richard between other work so put > this together quickly, but you're right this is going to be a pain to > backport/revert if issues so absolutely - will do. > > Since this is a hotfix I'm going to risk annoying people and shoot out > a v2 on same day as v1. Sorry in advance. > >> >> One review comment for the atomisp bits inline / below. >> >>> --- >>> drivers/net/ethernet/marvell/mvpp2/mvpp2.h | 2 +- >>> .../staging/media/atomisp/pci/sh_css_frac.h | 26 ++++++++++++++----- >>> include/linux/skbuff.h | 6 ++++- >>> 3 files changed, 25 insertions(+), 9 deletions(-) >>> >>> diff --git a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h >>> index e809f91c08fb..8b431f90efc3 100644 >>> --- a/drivers/net/ethernet/marvell/mvpp2/mvpp2.h >>> +++ b/drivers/net/ethernet/marvell/mvpp2/mvpp2.h >>> @@ -23,7 +23,7 @@ >>> /* The PacketOffset field is measured in units of 32 bytes and is 3 bits wide, >>> * so the maximum offset is 7 * 32 = 224 >>> */ >>> -#define MVPP2_SKB_HEADROOM min(max(XDP_PACKET_HEADROOM, NET_SKB_PAD), 224) >>> +#define MVPP2_SKB_HEADROOM clamp_t(int, XDP_PACKET_HEADROOM, NET_SKB_PAD, 224) >>> >>> #define MVPP2_XDP_PASS 0 >>> #define MVPP2_XDP_DROPPED BIT(0) >>> diff --git a/drivers/staging/media/atomisp/pci/sh_css_frac.h b/drivers/staging/media/atomisp/pci/sh_css_frac.h >>> index b90b5b330dfa..a973394c5bc0 100644 >>> --- a/drivers/staging/media/atomisp/pci/sh_css_frac.h >>> +++ b/drivers/staging/media/atomisp/pci/sh_css_frac.h >>> @@ -32,12 +32,24 @@ >>> #define uISP_VAL_MAX ((unsigned int)((1 << uISP_REG_BIT) - 1)) >>> >>> /* a:fraction bits for 16bit precision, b:fraction bits for ISP precision */ >>> -#define sDIGIT_FITTING(v, a, b) \ >>> - min_t(int, max_t(int, (((v) >> sSHIFT) >> max(sFRACTION_BITS_FITTING(a) - (b), 0)), \ >>> - sISP_VAL_MIN), sISP_VAL_MAX) >>> -#define uDIGIT_FITTING(v, a, b) \ >>> - min((unsigned int)max((unsigned)(((v) >> uSHIFT) \ >>> - >> max((int)(uFRACTION_BITS_FITTING(a) - (b)), 0)), \ >>> - uISP_VAL_MIN), uISP_VAL_MAX) >>> +static inline int sDIGIT_FITTING(short v, int a, int b) >>> +{ >> >> drivers/staging/media/atomisp/pci/isp/kernels/s3a/s3a_1.0/ia_css_s3a.host.c >> >> calls this with ia_css_3a_config.af_fir1_coef / .af_fir2_coef >> as first argument those are of the ia_css_s0_15 type which is: >> >> /* Signed fixed point value, 0 integer bits, 15 fractional bits */ >> typedef s32 ia_css_s0_15; >> >> please replace the "short v" with "int v" > > Yeah I think you're right, it's odd, because it seems that the shift value > and the comments implies that this is a short, but perhaps it's more so > that values are shifted as to obtain 16 bits of precision. > >> >> I think that you can then also replace clamp_t() with clamp() > > The use of clamp_t() is to avoid egregious macro expansion in > clamp(). After the series improving min/max the clamp() is probably > equivalent. But in 5.15 it will likely not be. So this is, in line with the > purpose of this change, I believe necesasry. Ok fair enough. Regards, Hans