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Tue, 07 Dec 2021 14:49:02 +0000 Date: Tue, 07 Dec 2021 14:49:02 +0000 Message-ID: <87ilw01ndt.wl-maz@kernel.org> From: Marc Zyngier To: Joey Gouly Cc: linux-arm-kernel@lists.infradead.org, nd@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, corbet@lwn.net, james.morse@arm.com, reijiw@google.com, suzuki.poulose@arm.com, will@kernel.org Subject: Re: [PATCH v2 2/3] arm64: add ID_AA64ISAR2_EL1 sys register In-Reply-To: <20211207143121.GA50552@e124191.cambridge.arm.com> References: <20211207124226.50095-1-joey.gouly@arm.com> <20211207124226.50095-3-joey.gouly@arm.com> <87lf0w1son.wl-maz@kernel.org> <20211207143121.GA50552@e124191.cambridge.arm.com> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/27.1 (x86_64-pc-linux-gnu) MULE/6.0 (HANACHIRUSATO) MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: joey.gouly@arm.com, linux-arm-kernel@lists.infradead.org, nd@arm.com, alexandru.elisei@arm.com, catalin.marinas@arm.com, corbet@lwn.net, james.morse@arm.com, reijiw@google.com, suzuki.poulose@arm.com, will@kernel.org X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20211207_064907_636719_BAF04DCD X-CRM114-Status: GOOD ( 26.33 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Tue, 07 Dec 2021 14:31:21 +0000, Joey Gouly wrote: > > Hi Marc, > > On Tue, Dec 07, 2021 at 12:54:32PM +0000, Marc Zyngier wrote: > > Hi Joey, > > > > On Tue, 07 Dec 2021 12:42:25 +0000, > > [...] > > > > diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h > > > index adcab9009f9d..5393a00340f5 100644 > > > --- a/arch/arm64/include/asm/sysreg.h > > > +++ b/arch/arm64/include/asm/sysreg.h > > > @@ -182,6 +182,7 @@ > > > > > > #define SYS_ID_AA64ISAR0_EL1 sys_reg(3, 0, 0, 6, 0) > > > #define SYS_ID_AA64ISAR1_EL1 sys_reg(3, 0, 0, 6, 1) > > > +#define SYS_ID_AA64ISAR2_EL1 sys_reg(3, 0, 0, 6, 2) > > > > > > #define SYS_ID_AA64MMFR0_EL1 sys_reg(3, 0, 0, 7, 0) > > > #define SYS_ID_AA64MMFR1_EL1 sys_reg(3, 0, 0, 7, 1) > > > @@ -771,6 +772,15 @@ > > > #define ID_AA64ISAR1_GPI_NI 0x0 > > > #define ID_AA64ISAR1_GPI_IMP_DEF 0x1 > > > > > > +/* id_aa64isar2 */ > > > +#define ID_AA64ISAR2_RPRES_SHIFT 4 > > > +#define ID_AA64ISAR2_WFXT_SHIFT 0 > > > + > > > +#define ID_AA64ISAR2_RPRES_8BIT 0x0 > > > +#define ID_AA64ISAR2_RPRES_12BIT 0x1 > > > +#define ID_AA64ISAR2_WFXT_NI 0x0 > > > +#define ID_AA64ISAR2_WFXT_SUPPORTED 0x2 > > > > Maybe I wasn't clear in my earlier comment: you need to enumerate all > > the architecturally valid values: > > > > #define ID_AA64ISAR2_WFXT_NI 0x0 > > #define ID_AA64ISAR2_WFXT_V1 0x1 > > #define ID_AA64ISAR2_WFXT_V2 0x2 > > > > where WFXT_V1 represent the original FEAT_WFxT, and WFXT_V2 the new, > > more usable FEAT_WFxT2. Even if the original FEAT_WFxT is deprecated, > > it still exists, and is still the only mandatory option for v8.7. > > The 0b001 behaviour has been removed from the architecture and is > now listed as reserved, but this has not made it's way into an ARM > ARM. The only permitted values are 0b000 and 0b0001 (mandatory in > v8.7) 0b0010, right? > > This can be seen from the documentation here: > https://developer.arm.com/documentation/ddi0601/2021-09/AArch64-Registers/ID-AA64ISAR2-EL1--AArch64-Instruction-Set-Attribute-Register-2?lang=en Yay for retrospective changes to the architecture! :D I guess that nobody dared building the broken version, so it's all good. Maybe add a small comment to that effect, so that people looking at outdated material don't get confused? Thanks, M. -- Without deviation from the norm, progress is not possible. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel