From: Marc Zyngier <maz@kernel.org>
To: Steven Price <steven.price@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, James Morse <james.morse@arm.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, Dave Martin <Dave.Martin@arm.com>,
Mark Rutland <mark.rutland@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
qemu-devel@nongnu.org, Juan Quintela <quintela@redhat.com>,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>,
Richard Henderson <richard.henderson@linaro.org>,
Peter Maydell <peter.maydell@linaro.org>,
Haibo Xu <Haibo.Xu@arm.com>, Andrew Jones <drjones@redhat.com>
Subject: Re: [PATCH v12 7/8] KVM: arm64: ioctl to fetch/store tags in a guest
Date: Mon, 17 May 2021 19:04:24 +0100 [thread overview]
Message-ID: <87sg2ltexj.wl-maz@kernel.org> (raw)
In-Reply-To: <20210517123239.8025-8-steven.price@arm.com>
On Mon, 17 May 2021 13:32:38 +0100,
Steven Price <steven.price@arm.com> wrote:
>
> The VMM may not wish to have it's own mapping of guest memory mapped
> with PROT_MTE because this causes problems if the VMM has tag checking
> enabled (the guest controls the tags in physical RAM and it's unlikely
> the tags are correct for the VMM).
>
> Instead add a new ioctl which allows the VMM to easily read/write the
> tags from guest memory, allowing the VMM's mapping to be non-PROT_MTE
> while the VMM can still read/write the tags for the purpose of
> migration.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/include/uapi/asm/kvm.h | 11 +++++
> arch/arm64/kvm/arm.c | 69 +++++++++++++++++++++++++++++++
> include/uapi/linux/kvm.h | 1 +
> 3 files changed, 81 insertions(+)
>
> 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..4b6c83beb75d 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1309,6 +1309,65 @@ static int kvm_vm_ioctl_set_device_addr(struct kvm *kvm,
> }
> }
>
> +static int kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
> + struct kvm_arm_copy_mte_tags *copy_tags)
> +{
> + gpa_t guest_ipa = copy_tags->guest_ipa;
> + size_t length = copy_tags->length;
> + void __user *tags = copy_tags->addr;
> + gpa_t gfn;
> + bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
> + int ret = 0;
> +
> + if (copy_tags->reserved[0] || copy_tags->reserved[1])
> + return -EINVAL;
> +
> + if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
> + return -EINVAL;
> +
> + if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
> + return -EINVAL;
> +
> + gfn = gpa_to_gfn(guest_ipa);
> +
> + mutex_lock(&kvm->slots_lock);
> +
> + while (length > 0) {
> + kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
> + void *maddr;
> + unsigned long num_tags = PAGE_SIZE / MTE_GRANULE_SIZE;
nit: this is a compile time constant, make it a #define. This will
avoid the confusing overloading of "num_tags" as both an input and an
output for the mte_copy_tags-* functions.
> +
> + if (is_error_noslot_pfn(pfn)) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + maddr = page_address(pfn_to_page(pfn));
> +
> + if (!write) {
> + num_tags = mte_copy_tags_to_user(tags, maddr, num_tags);
> + kvm_release_pfn_clean(pfn);
> + } else {
> + num_tags = mte_copy_tags_from_user(maddr, tags,
> + num_tags);
> + kvm_release_pfn_dirty(pfn);
> + }
> +
> + if (num_tags != PAGE_SIZE / MTE_GRANULE_SIZE) {
> + ret = -EFAULT;
> + goto out;
> + }
> +
> + gfn++;
> + tags += num_tags;
> + length -= PAGE_SIZE;
> + }
> +
> +out:
> + mutex_unlock(&kvm->slots_lock);
> + return ret;
> +}
> +
nit again: I'd really prefer it if you moved this to guest.c, where we
already have a bunch of the save/restore stuff.
> long kvm_arch_vm_ioctl(struct file *filp,
> unsigned int ioctl, unsigned long arg)
> {
> @@ -1345,6 +1404,16 @@ 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 (!kvm_has_mte(kvm))
> + return -EINVAL;
> +
> + if (copy_from_user(©_tags, argp, sizeof(copy_tags)))
> + return -EFAULT;
> + return kvm_vm_ioctl_mte_copy_tags(kvm, ©_tags);
> + }
> default:
> return -EINVAL;
> }
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8c95ba0fadda..4c011c60d468 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1428,6 +1428,7 @@ struct kvm_s390_ucas_mapping {
> /* Available with KVM_CAP_PMU_EVENT_FILTER */
> #define KVM_SET_PMU_EVENT_FILTER _IOW(KVMIO, 0xb2, struct kvm_pmu_event_filter)
> #define KVM_PPC_SVM_OFF _IO(KVMIO, 0xb3)
> +#define KVM_ARM_MTE_COPY_TAGS _IOR(KVMIO, 0xb4, struct kvm_arm_copy_mte_tags)
>
> /* ioctl for vm fd */
> #define KVM_CREATE_DEVICE _IOWR(KVMIO, 0xe0, struct kvm_create_device)
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2021-05-17 18:06 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-17 12:32 [PATCH v12 0/8] MTE support for KVM guest Steven Price
2021-05-17 12:32 ` [PATCH v12 1/8] arm64: mte: Handle race when synchronising tags Steven Price
2021-05-17 14:03 ` Marc Zyngier
2021-05-17 14:56 ` Steven Price
2021-05-19 17:32 ` Catalin Marinas
2021-05-17 12:32 ` [PATCH v12 2/8] arm64: Handle MTE tags zeroing in __alloc_zeroed_user_highpage() Steven Price
2021-05-17 12:32 ` [PATCH v12 3/8] arm64: mte: Sync tags for pages where PTE is untagged Steven Price
2021-05-17 16:14 ` Marc Zyngier
2021-05-19 9:32 ` Steven Price
2021-05-19 17:48 ` Catalin Marinas
2021-05-19 18:06 ` Catalin Marinas
2021-05-20 11:55 ` Steven Price
2021-05-20 12:25 ` Catalin Marinas
2021-05-20 13:02 ` Catalin Marinas
2021-05-20 13:03 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 4/8] arm64: kvm: Introduce MTE VM feature Steven Price
2021-05-17 16:45 ` Marc Zyngier
2021-05-19 10:48 ` Steven Price
2021-05-20 8:51 ` Marc Zyngier
2021-05-20 14:46 ` Steven Price
2021-05-20 11:54 ` Catalin Marinas
2021-05-20 15:05 ` Steven Price
2021-05-20 17:50 ` Catalin Marinas
2021-05-21 9:28 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 5/8] arm64: kvm: Save/restore MTE registers Steven Price
2021-05-17 17:17 ` Marc Zyngier
2021-05-19 13:04 ` Steven Price
2021-05-20 9:46 ` Marc Zyngier
2021-05-20 15:21 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 6/8] arm64: kvm: Expose KVM_ARM_CAP_MTE Steven Price
2021-05-17 17:40 ` Marc Zyngier
2021-05-19 13:26 ` Steven Price
2021-05-20 10:09 ` Marc Zyngier
2021-05-20 10:51 ` Steven Price
2021-05-17 12:32 ` [PATCH v12 7/8] KVM: arm64: ioctl to fetch/store tags in a guest Steven Price
2021-05-17 18:04 ` Marc Zyngier [this message]
2021-05-19 13:51 ` Steven Price
2021-05-20 12:05 ` Catalin Marinas
2021-05-20 15:58 ` Steven Price
2021-05-20 17:27 ` Catalin Marinas
2021-05-21 9:42 ` Steven Price
2021-05-24 18:11 ` Catalin Marinas
2021-05-27 7:50 ` Steven Price
2021-05-27 13:08 ` Catalin Marinas
2021-05-17 12:32 ` [PATCH v12 8/8] KVM: arm64: Document MTE capability and ioctl Steven Price
2021-05-17 18:09 ` Marc Zyngier
2021-05-19 14:09 ` Steven Price
2021-05-20 10:24 ` Marc Zyngier
2021-05-20 10:52 ` Steven Price
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87sg2ltexj.wl-maz@kernel.org \
--to=maz@kernel.org \
--cc=Dave.Martin@arm.com \
--cc=Haibo.Xu@arm.com \
--cc=catalin.marinas@arm.com \
--cc=dgilbert@redhat.com \
--cc=drjones@redhat.com \
--cc=james.morse@arm.com \
--cc=julien.thierry.kdev@gmail.com \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mark.rutland@arm.com \
--cc=peter.maydell@linaro.org \
--cc=qemu-devel@nongnu.org \
--cc=quintela@redhat.com \
--cc=richard.henderson@linaro.org \
--cc=steven.price@arm.com \
--cc=suzuki.poulose@arm.com \
--cc=tglx@linutronix.de \
--cc=will@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).