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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 1lp7pr-00DEaV-A2; Fri, 04 Jun 2021 11:17:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1lp7o1-00DDdS-LK for linux-arm-kernel@lists.infradead.org; Fri, 04 Jun 2021 11:16:03 +0000 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 168702B; Fri, 4 Jun 2021 04:16:00 -0700 (PDT) Received: from [192.168.1.179] (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 766343F73D; Fri, 4 Jun 2021 04:15:57 -0700 (PDT) Subject: Re: [PATCH v13 7/8] KVM: arm64: ioctl to fetch/store tags in a guest To: Catalin Marinas 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 References: <20210524104513.13258-1-steven.price@arm.com> <20210524104513.13258-8-steven.price@arm.com> <20210603171336.GH20338@arm.com> From: Steven Price Message-ID: <02c7682e-5fb6-29eb-9105-02e3521756a2@arm.com> Date: Fri, 4 Jun 2021 12:15:56 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210603171336.GH20338@arm.com> Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210604_041601_799353_01341342 X-CRM114-Status: GOOD ( 20.65 ) 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 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. Thanks, Steve _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel