| Message ID | 20210301142315.30920-3-steven.price@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | MTE support for KVM guest | expand |
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.
On 09/03/2021 17:06, Marc Zyngier wrote: > 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? Good point I guess this should have a (fault_status != FSC_PERM) in the test to match the other paths. >> + >> 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? Another good point - it would make sense to restrict this in case another MTE flavour is invented. Thanks, Steve >> 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. >
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)); + } + } + 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); 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
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(-)