| Message ID | 20201112222139.466204-1-maz@kernel.org |
|---|---|
| State | New |
| Headers | show |
On 12/11/20 23:21, Marc Zyngier wrote: > We now expose ID_AA64PFR0_EL1.CSV2=1 to guests running on hosts > that are immune to Spectre-v2, but that don't have this field set, > most likely because they predate the specification. > > However, this prevents the migration of guests that have started on > a host the doesn't fake this CSV2 setting to one that does, as KVM > rejects the write to ID_AA64PFR0_EL2 on the grounds that it isn't > what is already there. > > In order to fix this, allow userspace to set this field as long as > this doesn't result in a promising more than what is already there > (setting CSV2 to 0 is acceptable, but setting it to 1 when it is > already set to 0 isn't). > > Fixes: e1026237f9067 ("KVM: arm64: Set CSV2 for guests on hardware unaffected by Spectre-v2") > Reported-by: Peng Liang <liangpeng10@huawei.com> > Signed-off-by: Marc Zyngier <maz@kernel.org> > Acked-by: Will Deacon <will@kernel.org> > Link: https://lore.kernel.org/r/20201110141308.451654-2-maz@kernel.org > --- > arch/arm64/include/asm/kvm_host.h | 2 ++ > arch/arm64/kvm/arm.c | 16 ++++++++++++ > arch/arm64/kvm/sys_regs.c | 42 ++++++++++++++++++++++++++++--- > 3 files changed, 56 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h > index 781d029b8aa8..0cd9f0f75c13 100644 > --- a/arch/arm64/include/asm/kvm_host.h > +++ b/arch/arm64/include/asm/kvm_host.h > @@ -118,6 +118,8 @@ struct kvm_arch { > */ > unsigned long *pmu_filter; > unsigned int pmuver; > + > + u8 pfr0_csv2; > }; > > struct kvm_vcpu_fault_info { > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > index a3b32df1afb0..a6e25a4b4dc5 100644 > --- a/arch/arm64/kvm/arm.c > +++ b/arch/arm64/kvm/arm.c > @@ -102,6 +102,20 @@ static int kvm_arm_default_max_vcpus(void) > return vgic_present ? kvm_vgic_get_max_vcpus() : KVM_MAX_VCPUS; > } > > +static void set_default_csv2(struct kvm *kvm) > +{ > + /* > + * The default is to expose CSV2 == 1 if the HW isn't affected. > + * Although this is a per-CPU feature, we make it global because > + * asymmetric systems are just a nuisance. > + * > + * Userspace can override this as long as it doesn't promise > + * the impossible. > + */ > + if (arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED) > + kvm->arch.pfr0_csv2 = 1; > +} > + > /** > * kvm_arch_init_vm - initializes a VM data structure > * @kvm: pointer to the KVM struct > @@ -127,6 +141,8 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type) > /* The maximum number of VCPUs is limited by the host's GIC model */ > kvm->arch.max_vcpus = kvm_arm_default_max_vcpus(); > > + set_default_csv2(kvm); > + > return ret; > out_free_stage2_pgd: > kvm_free_stage2_pgd(&kvm->arch.mmu); > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > index 6d287eefd9f1..0aa86250e354 100644 > --- a/arch/arm64/kvm/sys_regs.c > +++ b/arch/arm64/kvm/sys_regs.c > @@ -1128,9 +1128,8 @@ static u64 read_id_reg(const struct kvm_vcpu *vcpu, > if (!vcpu_has_sve(vcpu)) > val &= ~(0xfUL << ID_AA64PFR0_SVE_SHIFT); > val &= ~(0xfUL << ID_AA64PFR0_AMU_SHIFT); > - if (!(val & (0xfUL << ID_AA64PFR0_CSV2_SHIFT)) && > - arm64_get_spectre_v2_state() == SPECTRE_UNAFFECTED) > - val |= (1UL << ID_AA64PFR0_CSV2_SHIFT); > + val &= ~(0xfUL << ID_AA64PFR0_CSV2_SHIFT); > + val |= ((u64)vcpu->kvm->arch.pfr0_csv2 << ID_AA64PFR0_CSV2_SHIFT); > } else if (id == SYS_ID_AA64PFR1_EL1) { > val &= ~(0xfUL << ID_AA64PFR1_MTE_SHIFT); > } else if (id == SYS_ID_AA64ISAR1_EL1 && !vcpu_has_ptrauth(vcpu)) { > @@ -1213,6 +1212,40 @@ static unsigned int sve_visibility(const struct kvm_vcpu *vcpu, > return REG_HIDDEN; > } > > +static int set_id_aa64pfr0_el1(struct kvm_vcpu *vcpu, > + const struct sys_reg_desc *rd, > + const struct kvm_one_reg *reg, void __user *uaddr) > +{ > + const u64 id = sys_reg_to_index(rd); > + int err; > + u64 val; > + u8 csv2; > + > + err = reg_from_user(&val, uaddr, id); > + if (err) > + return err; > + > + /* > + * Allow AA64PFR0_EL1.CSV2 to be set from userspace as long as > + * it doesn't promise more than what is actually provided (the > + * guest could otherwise be covered in ectoplasmic residue). > + */ > + csv2 = cpuid_feature_extract_unsigned_field(val, ID_AA64PFR0_CSV2_SHIFT); > + if (csv2 > 1 || > + (csv2 && arm64_get_spectre_v2_state() != SPECTRE_UNAFFECTED)) > + return -EINVAL; > + > + /* We can only differ with CSV2, and anything else is an error */ > + val ^= read_id_reg(vcpu, rd, false); > + val &= ~(0xFUL << ID_AA64PFR0_CSV2_SHIFT); > + if (val) > + return -EINVAL; > + > + vcpu->kvm->arch.pfr0_csv2 = csv2; > + > + return 0; > +} > + > /* > * cpufeature ID register user accessors > * > @@ -1472,7 +1505,8 @@ static const struct sys_reg_desc sys_reg_descs[] = { > > /* AArch64 ID registers */ > /* CRm=4 */ > - ID_SANITISED(ID_AA64PFR0_EL1), > + { SYS_DESC(SYS_ID_AA64PFR0_EL1), .access = access_id_reg, > + .get_user = get_id_reg, .set_user = set_id_aa64pfr0_el1, }, > ID_SANITISED(ID_AA64PFR1_EL1), > ID_UNALLOCATED(4,2), > ID_UNALLOCATED(4,3), > Pulled, thanks. Paolo
Paolo, Here's another small set of fixes for 5.10, this time fixing some corner cases of the Spectre mitigation rework. Note that I had to pull 5.10-rc1 into kvmarm/next in order to avoid some annoying conflicts. Please pull, M. The following changes since commit 4f6b838c378a52ea3ae0b15f12ca8a20849072fa: Merge tag 'v5.10-rc1' into kvmarm-master/next (2020-11-12 21:20:43 +0000) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git tags/kvmarm-fixes-5.10-3 for you to fetch changes up to ed4ffaf49bf9ce1002b516d8c6aa04937b7950bc: KVM: arm64: Handle SCXTNUM_ELx traps (2020-11-12 21:22:46 +0000) ---------------------------------------------------------------- KVM/arm64 fixes for v5.10, take #3 - Allow userspace to downgrade ID_AA64PFR0_EL1.CSV2 - Inject UNDEF on SCXTNUM_ELx access ---------------------------------------------------------------- Marc Zyngier (3): KVM: arm64: Allow setting of ID_AA64PFR0_EL1.CSV2 from userspace KVM: arm64: Unify trap handlers injecting an UNDEF KVM: arm64: Handle SCXTNUM_ELx traps arch/arm64/include/asm/kvm_host.h | 2 + arch/arm64/include/asm/sysreg.h | 4 ++ arch/arm64/kvm/arm.c | 16 ++++++ arch/arm64/kvm/sys_regs.c | 111 +++++++++++++++++++++++--------------- 4 files changed, 89 insertions(+), 44 deletions(-)