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spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References:Message-ID: Subject:To:From:Date:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=SVdrZDzmarneY5+ZIDoWfPjCinvQV3sRggc/HThxb30=; b=gcm40TjBVvrmrU/Wi5NI0AWhB BaetSP7waBl6m14pBX/umG85SdilxWFaFO0+yuPRYTAJKA197A7ppGT9LHMW0Ig4V/y54S3F5UvcU u8jUjjUpNZ5IP4IfpwiertcEZ+X83BhF9di+zinOwO4swk5/BGzcGB3YcoDsmIhd/VTg3yXsPIagh SqPefCvSHsZdyMfpZ6Vp69+JgQ5ath1cI25496HzOHg38x47oVBZG7Csd88jK8fQAMF0kz8CCsdv2 uK6WccKcpbnYXo/4t+eOASGOyp+Srw1Q52QcgJ/+JMP5pOv7W5XyhgLbJIY5cOZWrbKTk7snulFsV hOjV8VifA==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1l31NV-0003t6-E2; Fri, 22 Jan 2021 18:41:49 +0000 Received: from mail.kernel.org ([198.145.29.99]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1l31NT-0003sh-7j for linux-arm-kernel@lists.infradead.org; Fri, 22 Jan 2021 18:41:48 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id BBCB82376F; Fri, 22 Jan 2021 18:41:42 +0000 (UTC) Date: Fri, 22 Jan 2021 18:41:40 +0000 From: Catalin Marinas To: Marc Zyngier Subject: Re: [PATCH v4 09/21] arm64: cpufeature: Add global feature override facility Message-ID: <20210122184139.GG8567@gaia> References: <20210118094533.2874082-1-maz@kernel.org> <20210118094533.2874082-10-maz@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210118094533.2874082-10-maz@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210122_134147_411028_4D20064E X-CRM114-Status: GOOD ( 19.06 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Jing Zhang , Prasad Sodagudi , Srinivas Ramana , Suzuki K Poulose , Alexandru Elisei , linux-kernel@vger.kernel.org, Ard Biesheuvel , James Morse , Julien Thierry , Ajay Patil , kernel-team@android.com, David Brazdil , Will Deacon , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org 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 Mon, Jan 18, 2021 at 09:45:21AM +0000, Marc Zyngier wrote: > diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h > index 9a555809b89c..465d2cb63bfc 100644 > --- a/arch/arm64/include/asm/cpufeature.h > +++ b/arch/arm64/include/asm/cpufeature.h > @@ -75,6 +75,8 @@ struct arm64_ftr_reg { > u64 sys_val; > u64 user_val; > const struct arm64_ftr_bits *ftr_bits; > + u64 *override_val; > + u64 *override_mask; > }; > > extern struct arm64_ftr_reg arm64_ftr_reg_ctrel0; > diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c > index e99eddec0a46..aaa075c6f029 100644 > --- a/arch/arm64/kernel/cpufeature.c > +++ b/arch/arm64/kernel/cpufeature.c > @@ -544,13 +544,17 @@ static const struct arm64_ftr_bits ftr_raz[] = { > ARM64_FTR_END, > }; > > -#define ARM64_FTR_REG(id, table) { \ > - .sys_id = id, \ > - .reg = &(struct arm64_ftr_reg){ \ > - .name = #id, \ > - .ftr_bits = &((table)[0]), \ > +#define ARM64_FTR_REG_OVERRIDE(id, table, v, m) { \ > + .sys_id = id, \ > + .reg = &(struct arm64_ftr_reg){ \ > + .name = #id, \ > + .ftr_bits = &((table)[0]), \ > + .override_val = v, \ > + .override_mask = m, \ > }} > > +#define ARM64_FTR_REG(id, table) ARM64_FTR_REG_OVERRIDE(id, table, NULL, NULL) > + > static const struct __ftr_reg_entry { > u32 sys_id; > struct arm64_ftr_reg *reg; > @@ -760,6 +764,7 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) > u64 strict_mask = ~0x0ULL; > u64 user_mask = 0; > u64 valid_mask = 0; > + u64 override_val = 0, override_mask = 0; > > const struct arm64_ftr_bits *ftrp; > struct arm64_ftr_reg *reg = get_arm64_ftr_reg(sys_reg); > @@ -767,9 +772,38 @@ static void __init init_cpu_ftr_reg(u32 sys_reg, u64 new) > if (!reg) > return; > > + if (reg->override_mask && reg->override_val) { > + override_mask = *reg->override_mask; > + override_val = *reg->override_val; > + } > + > for (ftrp = reg->ftr_bits; ftrp->width; ftrp++) { > u64 ftr_mask = arm64_ftr_mask(ftrp); > s64 ftr_new = arm64_ftr_value(ftrp, new); > + s64 ftr_ovr = arm64_ftr_value(ftrp, override_val); > + > + if ((ftr_mask & override_mask) == ftr_mask) { > + s64 tmp = arm64_ftr_safe_value(ftrp, ftr_ovr, ftr_new); > + char *str = NULL; > + > + if (ftr_ovr != tmp) { > + /* Unsafe, remove the override */ > + *reg->override_mask &= ~ftr_mask; > + *reg->override_val &= ~ftr_mask; Do we need such clearing here? I don't think that's ever called again for this feature/reg. > + tmp = ftr_ovr; > + str = "ignoring override"; > + } else if (ftr_new != tmp) { > + /* Override was valid */ > + ftr_new = tmp; > + str = "forced"; > + } > + > + if (str) > + pr_warn("%s[%d:%d]: %s to %llx\n", > + reg->name, > + ftrp->shift + ftrp->width - 1, > + ftrp->shift, str, tmp); > + } > > val = arm64_ftr_set_value(ftrp, val, ftr_new); I wonder whether we could call, after init_cpu_ftr_reg(), a new function similar to update_cpu_ftr_reg() that takes a mask and value and leave init_cpu_ftr_reg() unchanged. The only advantage would be if we can get rid of the reg->override* fields. Anyway, I need to read the rest of the series to see whether it's possible. Otherwise this patch looks fine. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel