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a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724147632; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bnjw+ioMsX32W+/U+0afMGAjCJ8RkbI6twLdMA2W548=; b=Le5qJN+UCGkRhvQjiDT+PCWtWrNzSgUnc/TscXO6wgIRZye+zDS6+J2b5zKq7jnP1vq/8b uHu6TH9+/fEOr/MHdwr1QJ9GCxeaULR0uk0NfViBBVtret/ZhwN3SalZydu4OXl+SYRB3b z017W7Q261nAuEcWh31PGbsWPVYGyjk= Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 50B44DA7; Tue, 20 Aug 2024 02:55:15 -0700 (PDT) Received: from e124191.cambridge.arm.com (e124191.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 532323F66E; Tue, 20 Aug 2024 02:54:46 -0700 (PDT) Date: Tue, 20 Aug 2024 10:54:41 +0100 From: Joey Gouly To: Catalin Marinas Cc: Dave Martin , linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, aneesh.kumar@kernel.org, aneesh.kumar@linux.ibm.com, bp@alien8.de, broonie@kernel.org, christophe.leroy@csgroup.eu, dave.hansen@linux.intel.com, hpa@zytor.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, maz@kernel.org, mingo@redhat.com, mpe@ellerman.id.au, naveen.n.rao@linux.ibm.com, npiggin@gmail.com, oliver.upton@linux.dev, shuah@kernel.org, szabolcs.nagy@arm.com, tglx@linutronix.de, will@kernel.org, x86@kernel.org, kvmarm@lists.linux.dev Subject: Re: [PATCH v4 18/29] arm64: add POE signal support Message-ID: <20240820095441.GA688664@e124191.cambridge.arm.com> References: <20240503130147.1154804-19-joey.gouly@arm.com> <20240801155441.GB841837@e124191.cambridge.arm.com> <20240806103532.GA1986436@e124191.cambridge.arm.com> <20240806143103.GB2017741@e124191.cambridge.arm.com> <20240815131815.GA3657684@e124191.cambridge.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 4ABBD1C001D X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: g3s7f15x4p3wtczk48e3ys4pfi4zmz3y X-HE-Tag: 1724147690-803037 X-HE-Meta: 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 aoyP+zm3 BhxcVbWB1UXlQNVJpKiqM3J/k6zJrzrWEYCGb8Z8k2qzUYhqLkxNedAjYGL2vZCoCIjiZ7r+FKlnYv5gtE3k/IJ3FF2U1/Wcu5TC9192DjZkkLok3CcdcAqdtLj3V7yHooHseBqSdhdIrbkjYaUeF0sEFXw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 19, 2024 at 06:09:06PM +0100, Catalin Marinas wrote: > On Thu, Aug 15, 2024 at 04:09:26PM +0100, Dave P Martin wrote: > > On Thu, Aug 15, 2024 at 02:18:15PM +0100, Joey Gouly wrote: > > > That's a lot of words to say, or ask, do you agree with the approach of only > > > saving POR_EL0 in the signal frame if num_allocated_pkeys() > 1? > > > > > > Thanks, > > > Joey > > > > ...So..., given all the above, it is perhaps best to go back to > > dumping POR_EL0 unconditionally after all, unless we have a mechanism > > to determine whether pkeys are in use at all. > > Ah, I can see why checking for POR_EL0_INIT is useful. Only checking for > the allocated keys gets confusing with pkey 0. > > Not sure what the deal is with pkey 0. Is it considered allocated by > default or unallocatable? If the former, it implies that pkeys are > already in use (hence the additional check for POR_EL0_INIT). In > principle the hardware allows us to use permissions where the pkeys do > not apply but we'd run out of indices and PTE bits to encode them, so I > think by default we should assume that pkey 0 is pre-allocated. > > You can consider pkey 0 allocated by default. You can actually pkey_free(0), there's nothing stopping that. > So I agree that it's probably best to save it unconditionally. Alright, will leave it as is! Thanks, Joey