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[176.184.41.228]) by smtp.gmail.com with ESMTPSA id i3-20020adff303000000b0030795b2be15sm5648287wro.103.2023.05.19.09.08.31 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 19 May 2023 09:08:34 -0700 (PDT) Message-ID: <27f9ad4f-bdde-f548-860b-34e52493faa2@linaro.org> Date: Fri, 19 May 2023 18:08:30 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.11.0 Subject: Re: [PATCH v6 1/4] bswap: Add the ability to store to an unaligned 24 bit field Content-Language: en-US To: Jonathan Cameron , qemu-devel@nongnu.org, Michael Tsirkin , Fan Ni Cc: linux-cxl@vger.kernel.org, linuxarm@huawei.com, Ira Weiny , Michael Roth , Dave Jiang , Markus Armbruster , =?UTF-8?Q?Daniel_P_=2e_Berrang=c3=a9?= , Eric Blake , Mike Maslenkin , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , Thomas Huth References: <20230519141803.29713-1-Jonathan.Cameron@huawei.com> <20230519141803.29713-2-Jonathan.Cameron@huawei.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= In-Reply-To: <20230519141803.29713-2-Jonathan.Cameron@huawei.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::32a; envelope-from=philmd@linaro.org; helo=mail-wm1-x32a.google.com X-Spam_score_int: -35 X-Spam_score: -3.6 X-Spam_bar: --- X-Spam_report: (-3.6 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-1.527, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 19/5/23 16:18, Jonathan Cameron wrote: > From: Ira Weiny > > CXL has 24 bit unaligned fields which need to be stored to. CXL is > specified as little endian. > > Define st24_le_p() and the supporting functions to store such a field > from a 32 bit host native value. > > The use of b, w, l, q as the size specifier is limiting. So "24" was > used for the size part of the function name. > > Signed-off-by: Ira Weiny > Signed-off-by: Jonathan Cameron > --- > docs/devel/loads-stores.rst | 1 + > include/qemu/bswap.h | 27 +++++++++++++++++++++++++++ > 2 files changed, 28 insertions(+) > > diff --git a/docs/devel/loads-stores.rst b/docs/devel/loads-stores.rst > index d2cefc77a2..82a79e91d9 100644 > --- a/docs/devel/loads-stores.rst > +++ b/docs/devel/loads-stores.rst > @@ -36,6 +36,7 @@ store: ``st{size}_{endian}_p(ptr, val)`` > ``size`` > - ``b`` : 8 bits > - ``w`` : 16 bits > + - ``24`` : 24 bits > - ``l`` : 32 bits > - ``q`` : 64 bits > > diff --git a/include/qemu/bswap.h b/include/qemu/bswap.h > index 15a78c0db5..f546b1fc06 100644 > --- a/include/qemu/bswap.h > +++ b/include/qemu/bswap.h > @@ -8,11 +8,25 @@ > #undef bswap64 > #define bswap64(_x) __builtin_bswap64(_x) > > +static inline uint32_t bswap24(uint32_t x) > +{ > + assert((x & 0xff000000U) == 0); Asserting here is a bit violent. In particular because there is no contract description that x should be less than N bits for bswapN() in "qemu/bswap.h" API. But if you rather to assert ... > + > + return (((x & 0x000000ffU) << 16) | > + ((x & 0x0000ff00U) << 0) | > + ((x & 0x00ff0000U) >> 16)); > +} > + > static inline void bswap16s(uint16_t *s) > { > *s = __builtin_bswap16(*s); > } > > +static inline void bswap24s(uint32_t *s) > +{ > + *s = bswap24(*s & 0x00ffffffU); ... and sanitize the value here ... > +} > + > static inline void bswap32s(uint32_t *s) > { > *s = __builtin_bswap32(*s); > @@ -26,11 +40,13 @@ static inline void bswap64s(uint64_t *s) > #if HOST_BIG_ENDIAN > #define be_bswap(v, size) (v) > #define le_bswap(v, size) glue(__builtin_bswap, size)(v) > +#define le_bswap24(v) bswap24(v) ... then shouldn't you sanitize also here? Personally I'd just drop the assertion. > #define be_bswaps(v, size) > #define le_bswaps(p, size) \ > do { *p = glue(__builtin_bswap, size)(*p); } while (0) > #else > #define le_bswap(v, size) (v) > +#define le_bswap24(v) (v) > #define be_bswap(v, size) glue(__builtin_bswap, size)(v) > #define le_bswaps(v, size) > #define be_bswaps(p, size) \ > @@ -176,6 +192,7 @@ CPU_CONVERT(le, 64, uint64_t) > * size is: > * b: 8 bits > * w: 16 bits > + * 24: 24 bits > * l: 32 bits > * q: 64 bits > * > @@ -248,6 +265,11 @@ static inline void stw_he_p(void *ptr, uint16_t v) > __builtin_memcpy(ptr, &v, sizeof(v)); > } > > +static inline void st24_he_p(void *ptr, uint32_t v) > +{ > + __builtin_memcpy(ptr, &v, 3); > +} > + > static inline int ldl_he_p(const void *ptr) > { > int32_t r; > @@ -297,6 +319,11 @@ static inline void stw_le_p(void *ptr, uint16_t v) > stw_he_p(ptr, le_bswap(v, 16)); > } > > +static inline void st24_le_p(void *ptr, uint32_t v) > +{ > + st24_he_p(ptr, le_bswap24(v)); > +} > + > static inline void stl_le_p(void *ptr, uint32_t v) > { > stl_he_p(ptr, le_bswap(v, 32)); Conditional to removing the assertion in bswap24(): Reviewed-by: Philippe Mathieu-Daudé