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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lp8Du-00DNdO-Th; Fri, 04 Jun 2021 11:42:47 +0000 Received: from mail.kernel.org ([198.145.29.99]) by bombadil.infradead.org with esmtps (Exim 4.94.2 #2 (Red Hat Linux)) id 1lp8Do-00DNc7-By for linux-arm-kernel@lists.infradead.org; Fri, 04 Jun 2021 11:42:41 +0000 Received: by mail.kernel.org (Postfix) with ESMTPSA id 89B72613E9; Fri, 4 Jun 2021 11:42:36 +0000 (UTC) Date: Fri, 4 Jun 2021 12:42:34 +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 v13 7/8] KVM: arm64: ioctl to fetch/store tags in a guest Message-ID: <20210604114233.GE31173@arm.com> References: <20210524104513.13258-1-steven.price@arm.com> <20210524104513.13258-8-steven.price@arm.com> <20210603171336.GH20338@arm.com> <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> 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-20210604_044240_463667_32585678 X-CRM114-Status: GOOD ( 23.99 ) 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 Fri, Jun 04, 2021 at 12:15:56PM +0100, Steven Price wrote: > On 03/06/2021 18:13, Catalin Marinas wrote: > > On Mon, May 24, 2021 at 11:45:12AM +0100, Steven Price wrote: > >> diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h > >> index 24223adae150..b3edde68bc3e 100644 > >> --- a/arch/arm64/include/uapi/asm/kvm.h > >> +++ b/arch/arm64/include/uapi/asm/kvm.h > >> @@ -184,6 +184,17 @@ struct kvm_vcpu_events { > >> __u32 reserved[12]; > >> }; > >> > >> +struct kvm_arm_copy_mte_tags { > >> + __u64 guest_ipa; > >> + __u64 length; > >> + void __user *addr; > >> + __u64 flags; > >> + __u64 reserved[2]; > >> +}; > >> + > >> +#define KVM_ARM_TAGS_TO_GUEST 0 > >> +#define KVM_ARM_TAGS_FROM_GUEST 1 > >> + > >> /* If you need to interpret the index values, here is the key: */ > >> #define KVM_REG_ARM_COPROC_MASK 0x000000000FFF0000 > >> #define KVM_REG_ARM_COPROC_SHIFT 16 > >> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > >> index e89a5e275e25..baa33359e477 100644 > >> --- a/arch/arm64/kvm/arm.c > >> +++ b/arch/arm64/kvm/arm.c > >> @@ -1345,6 +1345,13 @@ long kvm_arch_vm_ioctl(struct file *filp, > >> > >> return 0; > >> } > >> + case KVM_ARM_MTE_COPY_TAGS: { > >> + struct kvm_arm_copy_mte_tags copy_tags; > >> + > >> + if (copy_from_user(©_tags, argp, sizeof(copy_tags))) > >> + return -EFAULT; > >> + return kvm_vm_ioctl_mte_copy_tags(kvm, ©_tags); > >> + } > > > > I wonder whether we need an update of the user structure following a > > fault, like how much was copied etc. In case of an error, some tags were > > copied and the VMM may want to skip the page before continuing. But here > > there's no such information provided. > > > > On the ptrace interface, we return 0 on the syscall if any bytes were > > copied and update iov_len to such number. Maybe you want to still return > > an error here but updating copy_tags.length would be nice (and, of > > course, a copy_to_user() back). > > Good idea - as you suggest I'll make it update length with the number of > bytes not processed. Although in general I think we're expecting the VMM > to know where the memory is so this is more of a programming error - but > could still be useful for debugging. Or update it to the number of bytes copied to be consistent with ptrace()'s iov.len. On success, the structure is effectively left unchanged. -- Catalin _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel