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| From: | Steven Price |
| Subject: | Re: [PATCH v2 2/2] arm64: kvm: Introduce MTE VCPU feature |
| Date: | Thu, 10 Sep 2020 10:21:07 +0100 |
| User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 |
On 09/09/2020 16:48, Andrew Jones wrote:
On Fri, Sep 04, 2020 at 05:00:18PM +0100, Steven Price wrote:Add a new VCPU features 'KVM_ARM_VCPU_MTE' which enables memory tagging on a VCPU. When enabled on any VCPU in the virtual machine this causes all pages that are faulted into the VM to have the PG_mte_tagged flag set (and the tag storage cleared if this is the first use). Signed-off-by: Steven Price <steven.price@arm.com> --- arch/arm64/include/asm/kvm_emulate.h | 3 +++ arch/arm64/include/asm/kvm_host.h | 5 ++++- arch/arm64/include/uapi/asm/kvm.h | 1 + arch/arm64/kvm/mmu.c | 15 +++++++++++++++ arch/arm64/kvm/reset.c | 8 ++++++++ arch/arm64/kvm/sys_regs.c | 6 +++++- 6 files changed, 36 insertions(+), 2 deletions(-) diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index 49a55be2b9a2..0042323a4b7f 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -79,6 +79,9 @@ 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 (test_bit(KVM_ARM_VCPU_MTE, vcpu->arch.features)) + 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 4f4360dd149e..b1190366242b 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -37,7 +37,7 @@#define KVM_MAX_VCPUS VGIC_V3_MAX_CPUS -#define KVM_VCPU_MAX_FEATURES 7+#define KVM_VCPU_MAX_FEATURES 8#define KVM_REQ_SLEEP \KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP) @@ -110,6 +110,9 @@ struct kvm_arch { * supported. */ bool return_nisv_io_abort_to_user; + + /* If any VCPU has MTE enabled then all memory must be MTE enabled */ + bool vcpu_has_mte;It looks like this is unnecessary as it's only used once, where a feature check could be used.
It's used in user_mem_abort(), so every time we fault a page into the VM - so having to iterate over all VCPUs to check if any have the feature bit set seems too expensive.
Although perhaps I should just accept that this is realistically a VM setting and move it out of the VCPU.
};struct kvm_vcpu_fault_info {diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index ba85bb23f060..2677e1ab8c16 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -106,6 +106,7 @@ struct kvm_regs { #define KVM_ARM_VCPU_SVE 4 /* enable SVE for this CPU */ #define KVM_ARM_VCPU_PTRAUTH_ADDRESS 5 /* VCPU uses address authentication */ #define KVM_ARM_VCPU_PTRAUTH_GENERIC 6 /* VCPU uses generic authentication */ +#define KVM_ARM_VCPU_MTE 7 /* VCPU supports Memory Tagging */struct kvm_vcpu_init {__u32 target; diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index ba00bcc0c884..e8891bacd76f 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1949,6 +1949,21 @@ 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 (system_supports_mte() && kvm->arch.vcpu_has_mte && pfn_valid(pfn)) { + /* + * VM will be able to see the page's tags, so we must ensure + * they have been initialised. + */ + struct page *page = pfn_to_page(pfn); + long i, nr_pages = compound_nr(page); + + /* if PG_mte_tagged is set, tags have already been initialised */ + 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)); + } + } + if (writable) kvm_set_pfn_dirty(pfn);diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.cindex ee33875c5c2a..82f3883d717f 100644 --- a/arch/arm64/kvm/reset.c +++ b/arch/arm64/kvm/reset.c @@ -274,6 +274,14 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu) } }+ if (test_bit(KVM_ARM_VCPU_MTE, vcpu->arch.features)) {+ if (!system_supports_mte()) { + ret = -EINVAL; + goto out; + } + vcpu->kvm->arch.vcpu_has_mte = true; + }We either need a KVM cap or a new CPU feature probing interface to avoid making userspace try features one at a time. It's too bad that VCPU_INIT doesn't clear all offending features from the feature set when returning EINVAL, because then userspace could create a scratch VCPU with everything it supports in order to see what KVM also supports in one go.
If Peter's TELL_ME_WHAT_YOU_HAVE idea works out then perhaps we don't need the cap? Or would it still be useful?
Thanks, Steve
+ switch (vcpu->arch.target) { default: if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features)) { diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c index a655f172b5ad..6a971b201e81 100644 --- a/arch/arm64/kvm/sys_regs.c +++ b/arch/arm64/kvm/sys_regs.c @@ -1132,7 +1132,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT); val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT); } else if (id == SYS_ID_AA64PFR1_EL1) { - val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT); + if (!test_bit(KVM_ARM_VCPU_MTE, vcpu->arch.features)) + val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT); } else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) { val &= ~((0xfUL << ID_AA64ISAR1_APA_SHIFT) | (0xfUL << ID_AA64ISAR1_API_SHIFT) | @@ -1394,6 +1395,9 @@ static bool access_mte_regs(struct kvm_vcpu *vcpu, struct sys_reg_params *p, static unsigned int mte_visibility(const struct kvm_vcpu *vcpu, const struct sys_reg_desc *rd) { + if (test_bit(KVM_ARM_VCPU_MTE, vcpu->arch.features)) + return 0; + return REG_HIDDEN_USER | REG_HIDDEN_GUEST; }--2.20.1 _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarmThanks, drew
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