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Tue, 04 May 2021 17:44:44 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9249C61166; Tue, 4 May 2021 17:44:39 +0000 (UTC) Date: Tue, 4 May 2021 18:44:37 +0100 From: Catalin Marinas To: Steven Price Cc: Marc Zyngier , Will Deacon , James Morse , Julien Thierry , Suzuki K Poulose , kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Dave Martin , Mark Rutland , Thomas Gleixner , qemu-devel@nongnu.org, Juan Quintela , "Dr. David Alan Gilbert" , Richard Henderson , Peter Maydell , Haibo Xu , Andrew Jones Subject: Re: [PATCH v11 5/6] KVM: arm64: ioctl to fetch/store tags in a guest Message-ID: References: <20210416154309.22129-1-steven.price@arm.com> <20210416154309.22129-6-steven.price@arm.com> <20210427175844.GB17872@arm.com> <340d35c2-46ed-35ea-43fa-e5cb64c27230@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <340d35c2-46ed-35ea-43fa-e5cb64c27230@arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210504_104443_038639_ECB51396 X-CRM114-Status: GOOD ( 17.90 ) 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 Thu, Apr 29, 2021 at 05:06:07PM +0100, Steven Price wrote: > On 27/04/2021 18:58, Catalin Marinas wrote: > > On Fri, Apr 16, 2021 at 04:43:08PM +0100, Steven Price wrote: > > > diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > > > index 24223adae150..2b85a047c37d 100644 > > > --- a/arch/arm64/include/uapi/asm/kvm.h > > > +++ b/arch/arm64/include/uapi/asm/kvm.h > > > @@ -184,6 +184,20 @@ struct kvm_vcpu_events { > > > __u32 reserved[12]; > > > }; > > > +struct kvm_arm_copy_mte_tags { > > > + __u64 guest_ipa; > > > + __u64 length; > > > + union { > > > + void __user *addr; > > > + __u64 padding; > > > + }; > > > + __u64 flags; > > > + __u64 reserved[2]; > > > +}; [...] > > Maybe add the two reserved > > values to the union in case we want to store something else in the > > future. > > I'm not sure what you mean here. What would the reserved fields be unioned > with? And surely they are no longer reserved in that case? In case you want to keep the structure size the same for future expansion and the expansion only happens via the union, you'd add some padding in there just in case. We do this for struct siginfo with an _si_pad[] array in the union. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel