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 v9 2/6] arm64: kvm: Introduce MTE VM feature
Date: Tue, 09 Mar 2021 17:06:23 +0000 [thread overview]
Message-ID: <87im60xnn4.wl-maz@kernel.org> (raw)
In-Reply-To: <20210301142315.30920-3-steven.price@arm.com>
On Mon, 01 Mar 2021 14:23:11 +0000,
Steven Price <steven.price@arm.com> wrote:
>
> Add a new VM feature 'KVM_ARM_CAP_MTE' which enables memory tagging
> for a VM. This will expose the feature to the guest and automatically
> tag memory pages touched by the VM as PG_mte_tagged (and clear the tag
> storage) to ensure that the guest cannot see stale tags, and so that
> the tags are correctly saved/restored across swap.
>
> Actually exposing the new capability to user space happens in a later
> patch.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/include/asm/kvm_emulate.h | 3 +++
> arch/arm64/include/asm/kvm_host.h | 3 +++
> arch/arm64/kvm/hyp/exception.c | 3 ++-
> arch/arm64/kvm/mmu.c | 16 ++++++++++++++++
> arch/arm64/kvm/sys_regs.c | 3 ++-
> include/uapi/linux/kvm.h | 1 +
> 6 files changed, 27 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index f612c090f2e4..6bf776c2399c 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -84,6 +84,9 @@ static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
> if (cpus_have_const_cap(ARM64_MISMATCHED_CACHE_TYPE) ||
> vcpu_el1_is_32bit(vcpu))
> vcpu->arch.hcr_el2 |= HCR_TID2;
> +
> + if (kvm_has_mte(vcpu->kvm))
> + vcpu->arch.hcr_el2 |= HCR_ATA;
> }
>
> static inline unsigned long *vcpu_hcr(struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 3d10e6527f7d..1170ee137096 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -132,6 +132,8 @@ struct kvm_arch {
>
> u8 pfr0_csv2;
> u8 pfr0_csv3;
> + /* Memory Tagging Extension enabled for the guest */
> + bool mte_enabled;
> };
>
> struct kvm_vcpu_fault_info {
> @@ -767,6 +769,7 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu);
> #define kvm_arm_vcpu_sve_finalized(vcpu) \
> ((vcpu)->arch.flags & KVM_ARM64_VCPU_SVE_FINALIZED)
>
> +#define kvm_has_mte(kvm) (system_supports_mte() && (kvm)->arch.mte_enabled)
> #define kvm_vcpu_has_pmu(vcpu) \
> (test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))
>
> diff --git a/arch/arm64/kvm/hyp/exception.c b/arch/arm64/kvm/hyp/exception.c
> index 73629094f903..56426565600c 100644
> --- a/arch/arm64/kvm/hyp/exception.c
> +++ b/arch/arm64/kvm/hyp/exception.c
> @@ -112,7 +112,8 @@ static void enter_exception64(struct kvm_vcpu *vcpu, unsigned long target_mode,
> new |= (old & PSR_C_BIT);
> new |= (old & PSR_V_BIT);
>
> - // TODO: TCO (if/when ARMv8.5-MemTag is exposed to guests)
> + if (kvm_has_mte(vcpu->kvm))
> + new |= PSR_TCO_BIT;
>
> new |= (old & PSR_DIT_BIT);
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 77cb2d28f2a4..fdb6ab604fd0 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -879,6 +879,22 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> if (vma_pagesize == PAGE_SIZE && !force_pte)
> vma_pagesize = transparent_hugepage_adjust(memslot, hva,
> &pfn, &fault_ipa);
> +
> + if (kvm_has_mte(kvm) && pfn_valid(pfn)) {
> + /*
> + * VM will be able to see the page's tags, so we must ensure
> + * they have been initialised. if PG_mte_tagged is set, tags
> + * have already been initialised.
> + */
> + struct page *page = pfn_to_page(pfn);
> + unsigned long i, nr_pages = vma_pagesize >> PAGE_SHIFT;
> +
> + for (i = 0; i < nr_pages; i++, page++) {
> + if (!test_and_set_bit(PG_mte_tagged, &page->flags))
> + mte_clear_page_tags(page_address(page));
> + }
> + }
Is there any reason to do this dance for anything but a translation
fault?
> +
> if (writable)
> prot |= KVM_PGTABLE_PROT_W;
>
> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> index 4f2f1e3145de..e09dbc00b0a2 100644
> --- a/arch/arm64/kvm/sys_regs.c
> +++ b/arch/arm64/kvm/sys_regs.c
> @@ -1046,7 +1046,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu,
> val |= FIELD_PREP(FEATURE(ID_AA64PFR0_CSV3), (u64)vcpu->kvm->arch.pfr0_csv3);
> break;
> case SYS_ID_AA64PFR1_EL1:
> - val &= ~FEATURE(ID_AA64PFR1_MTE);
> + if (!kvm_has_mte(vcpu->kvm))
> + val &= ~FEATURE(ID_AA64PFR1_MTE);
Are we happy to expose *any* of the MTE flavours? Or should we
restrict it in any way?
> break;
> case SYS_ID_AA64ISAR1_EL1:
> if (!vcpu_has_ptrauth(vcpu))
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8b281f722e5b..05618a4abf7e 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1078,6 +1078,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_DIRTY_LOG_RING 192
> #define KVM_CAP_X86_BUS_LOCK_EXIT 193
> #define KVM_CAP_PPC_DAWR1 194
> +#define KVM_CAP_ARM_MTE 195
>
> #ifdef KVM_CAP_IRQ_ROUTING
>
> --
> 2.20.1
>
>
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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next prev parent reply other threads:[~2021-03-09 17:08 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-01 14:23 [PATCH v9 0/6] MTE support for KVM guest Steven Price
2021-03-01 14:23 ` [PATCH v9 1/6] arm64: mte: Sync tags for pages where PTE is untagged Steven Price
2021-03-01 14:23 ` [PATCH v9 2/6] arm64: kvm: Introduce MTE VM feature Steven Price
2021-03-09 17:06 ` Marc Zyngier [this message]
2021-03-10 14:52 ` Steven Price
2021-03-01 14:23 ` [PATCH v9 3/6] arm64: kvm: Save/restore MTE registers Steven Price
2021-03-09 17:27 ` Marc Zyngier
2021-03-10 14:53 ` Steven Price
2021-03-01 14:23 ` [PATCH v9 4/6] arm64: kvm: Expose KVM_ARM_CAP_MTE Steven Price
2021-03-01 14:23 ` [PATCH v9 5/6] KVM: arm64: ioctl to fetch/store tags in a guest Steven Price
2021-03-09 17:57 ` Marc Zyngier
2021-03-10 16:47 ` Steven Price
2021-03-01 14:23 ` [PATCH v9 6/6] KVM: arm64: Document MTE capability and ioctl Steven Price
2021-03-09 11:01 ` Peter Maydell
2021-03-11 12:35 ` Steven Price
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