HI Shameerali, On Fri, May 19, 2023 at 1:08 AM Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> wrote: > > > > > -----Original Message----- > > From: Jing Zhang [mailto:jingzhangos@xxxxxxxxxx] > > Sent: 18 May 2023 20:49 > > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > > Cc: KVM <kvm@xxxxxxxxxxxxxxx>; KVMARM <kvmarm@xxxxxxxxxxxxxxx>; > > ARMLinux <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Marc Zyngier > > <maz@xxxxxxxxxx>; Oliver Upton <oupton@xxxxxxxxxx>; Will Deacon > > <will@xxxxxxxxxx>; Paolo Bonzini <pbonzini@xxxxxxxxxx>; James Morse > > <james.morse@xxxxxxx>; Alexandru Elisei <alexandru.elisei@xxxxxxx>; > > Suzuki K Poulose <suzuki.poulose@xxxxxxx>; Fuad Tabba > > <tabba@xxxxxxxxxx>; Reiji Watanabe <reijiw@xxxxxxxxxx>; Raghavendra > > Rao Ananta <rananta@xxxxxxxxxx> > > Subject: Re: [PATCH v9 1/5] KVM: arm64: Save ID registers' sanitized value > > per guest > > > > Hi Shameerali, > > > > On Thu, May 18, 2023 at 12:17 AM Shameerali Kolothum Thodi > > <shameerali.kolothum.thodi@xxxxxxxxxx> wrote: > > > > > > > > > > > > > -----Original Message----- > > > > From: Jing Zhang [mailto:jingzhangos@xxxxxxxxxx] > > > > Sent: 17 May 2023 07:10 > > > > To: KVM <kvm@xxxxxxxxxxxxxxx>; KVMARM <kvmarm@xxxxxxxxxxxxxxx>; > > > > ARMLinux <linux-arm-kernel@xxxxxxxxxxxxxxxxxxx>; Marc Zyngier > > > > <maz@xxxxxxxxxx>; Oliver Upton <oupton@xxxxxxxxxx> > > > > Cc: Will Deacon <will@xxxxxxxxxx>; Paolo Bonzini > > <pbonzini@xxxxxxxxxx>; > > > > James Morse <james.morse@xxxxxxx>; Alexandru Elisei > > > > <alexandru.elisei@xxxxxxx>; Suzuki K Poulose > > <suzuki.poulose@xxxxxxx>; > > > > Fuad Tabba <tabba@xxxxxxxxxx>; Reiji Watanabe <reijiw@xxxxxxxxxx>; > > > > Raghavendra Rao Ananta <rananta@xxxxxxxxxx>; Jing Zhang > > > > <jingzhangos@xxxxxxxxxx> > > > > Subject: [PATCH v9 1/5] KVM: arm64: Save ID registers' sanitized value > > per > > > > guest > > > > > > > > Introduce id_regs[] in kvm_arch as a storage of guest's ID registers, > > > > and save ID registers' sanitized value in the array at KVM_CREATE_VM. > > > > Use the saved ones when ID registers are read by the guest or > > > > userspace (via KVM_GET_ONE_REG). > > > > > > > > No functional change intended. > > > > > > > > Co-developed-by: Reiji Watanabe <reijiw@xxxxxxxxxx> > > > > Signed-off-by: Reiji Watanabe <reijiw@xxxxxxxxxx> > > > > Signed-off-by: Jing Zhang <jingzhangos@xxxxxxxxxx> > > > > --- > > > > arch/arm64/include/asm/kvm_host.h | 20 +++++++++ > > > > arch/arm64/kvm/arm.c | 1 + > > > > arch/arm64/kvm/sys_regs.c | 69 > > > > +++++++++++++++++++++++++------ > > > > arch/arm64/kvm/sys_regs.h | 7 ++++ > > > > 4 files changed, 85 insertions(+), 12 deletions(-) > > > > > > > > diff --git a/arch/arm64/include/asm/kvm_host.h > > > > b/arch/arm64/include/asm/kvm_host.h > > > > index 7e7e19ef6993..949a4a782844 100644 > > > > --- a/arch/arm64/include/asm/kvm_host.h > > > > +++ b/arch/arm64/include/asm/kvm_host.h > > > > @@ -178,6 +178,21 @@ struct kvm_smccc_features { > > > > unsigned long vendor_hyp_bmap; > > > > }; > > > > > > > > +/* > > > > + * Emulated CPU ID registers per VM > > > > + * (Op0, Op1, CRn, CRm, Op2) of the ID registers to be saved in it > > > > + * is (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8. > > > > + * > > > > + * These emulated idregs are VM-wide, but accessed from the context of > > a > > > > vCPU. > > > > + * Access to id regs are guarded by kvm_arch.config_lock. > > > > + */ > > > > +#define KVM_ARM_ID_REG_NUM 56 > > > > +#define IDREG_IDX(id) (((sys_reg_CRm(id) - 1) << 3) | > > sys_reg_Op2(id)) > > > > +#define IDREG(kvm, id) > > ((kvm)->arch.idregs.regs[IDREG_IDX(id)]) > > > > +struct kvm_idregs { > > > > + u64 regs[KVM_ARM_ID_REG_NUM]; > > > > +}; > > > > > > > > > > Not sure we really need this struct here. Why can't this array be moved to > > > struct kvm_arch directly? > > It was put in kvm_arch directly before, then got into its own > > structure in v5 according to the comments here: > > https://lore.kernel.org/all/861qlaxzyw.wl-maz@xxxxxxxxxx/#t > > Ok. > > > > > typedef unsigned int pkvm_handle_t; > > > > > > > > struct kvm_protected_vm { > > > > @@ -253,6 +268,9 @@ struct kvm_arch { > > > > struct kvm_smccc_features smccc_feat; > > > > struct maple_tree smccc_filter; > > > > > > > > + /* Emulated CPU ID registers */ > > > > + struct kvm_idregs idregs; > > > > + > > > > /* > > > > * For an untrusted host VM, 'pkvm.handle' is used to lookup > > > > * the associated pKVM instance in the hypervisor. > > > > @@ -1045,6 +1063,8 @@ int kvm_vm_ioctl_mte_copy_tags(struct kvm > > > > *kvm, > > > > int kvm_vm_ioctl_set_counter_offset(struct kvm *kvm, > > > > struct kvm_arm_counter_offset > > *offset); > > > > > > > > +void kvm_arm_init_id_regs(struct kvm *kvm); > > > > + > > > > /* Guest/host FPSIMD coordination helpers */ > > > > int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu); > > > > void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu); > > > > diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c > > > > index 14391826241c..774656a0718d 100644 > > > > --- a/arch/arm64/kvm/arm.c > > > > +++ b/arch/arm64/kvm/arm.c > > > > @@ -163,6 +163,7 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned > > > > long type) > > > > > > > > set_default_spectre(kvm); > > > > kvm_arm_init_hypercalls(kvm); > > > > + kvm_arm_init_id_regs(kvm); > > > > > > > > /* > > > > * Initialise the default PMUver before there is a chance to > > > > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c > > > > index 71b12094d613..d2ee3a1c7f03 100644 > > > > --- a/arch/arm64/kvm/sys_regs.c > > > > +++ b/arch/arm64/kvm/sys_regs.c > > > > @@ -41,6 +41,7 @@ > > > > * 64bit interface. > > > > */ > > > > > > > > +static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id); > > > > static u64 sys_reg_to_index(const struct sys_reg_desc *reg); > > > > > > > > static bool read_from_write_only(struct kvm_vcpu *vcpu, > > > > @@ -364,7 +365,7 @@ static bool trap_loregion(struct kvm_vcpu *vcpu, > > > > struct sys_reg_params *p, > > > > const struct sys_reg_desc *r) > > > > { > > > > - u64 val = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1); > > > > + u64 val = kvm_arm_read_id_reg(vcpu, SYS_ID_AA64MMFR1_EL1); > > > > u32 sr = reg_to_encoding(r); > > > > > > > > if (!(val & (0xfUL << ID_AA64MMFR1_EL1_LO_SHIFT))) { > > > > @@ -1208,16 +1209,9 @@ static u8 pmuver_to_perfmon(u8 pmuver) > > > > } > > > > } > > > > > > > > -/* Read a sanitised cpufeature ID register by sys_reg_desc */ > > > > -static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct sys_reg_desc > > > > const *r) > > > > +static u64 kvm_arm_read_id_reg(const struct kvm_vcpu *vcpu, u32 id) > > > > { > > > > - u32 id = reg_to_encoding(r); > > > > - u64 val; > > > > - > > > > - if (sysreg_visible_as_raz(vcpu, r)) > > > > - return 0; > > > > - > > > > - val = read_sanitised_ftr_reg(id); > > > > + u64 val = IDREG(vcpu->kvm, id); > > > > > > > > switch (id) { > > > > case SYS_ID_AA64PFR0_EL1: > > > > @@ -1280,6 +1274,26 @@ static u64 read_id_reg(const struct > > kvm_vcpu > > > > *vcpu, struct sys_reg_desc const *r > > > > return val; > > > > } > > > > > > > > +/* Read a sanitised cpufeature ID register by sys_reg_desc */ > > > > +static u64 read_id_reg(const struct kvm_vcpu *vcpu, struct > > sys_reg_desc > > > > const *r) > > > > +{ > > > > + if (sysreg_visible_as_raz(vcpu, r)) > > > > + return 0; > > > > + > > > > + return kvm_arm_read_id_reg(vcpu, reg_to_encoding(r)); > > > > +} > > > > + > > > > +/* > > > > + * Return true if the register's (Op0, Op1, CRn, CRm, Op2) is > > > > + * (3, 0, 0, crm, op2), where 1<=crm<8, 0<=op2<8. > > > > + */ > > > > +static inline bool is_id_reg(u32 id) > > > > +{ > > > > + return (sys_reg_Op0(id) == 3 && sys_reg_Op1(id) == 0 && > > > > + sys_reg_CRn(id) == 0 && sys_reg_CRm(id) >= 1 && > > > > + sys_reg_CRm(id) < 8); > > > > +} > > > > + > > > > static unsigned int id_visibility(const struct kvm_vcpu *vcpu, > > > > const struct sys_reg_desc *r) > > > > { > > > > @@ -2244,8 +2258,8 @@ static bool trap_dbgdidr(struct kvm_vcpu > > *vcpu, > > > > if (p->is_write) { > > > > return ignore_write(vcpu, p); > > > > } else { > > > > - u64 dfr = > > read_sanitised_ftr_reg(SYS_ID_AA64DFR0_EL1); > > > > - u64 pfr = > > read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1); > > > > + u64 dfr = kvm_arm_read_id_reg(vcpu, > > SYS_ID_AA64DFR0_EL1); > > > > + u64 pfr = kvm_arm_read_id_reg(vcpu, > > SYS_ID_AA64PFR0_EL1); > > > > > > Does this change the behavior slightly as now within the > > kvm_arm_read_id_reg() > > > the val will be further adjusted based on KVM/vCPU? > > That's a good question. Although the actual behavior would be the same > > no matter read idreg with read_sanitised_ftr_reg or > > kvm_arm_read_id_reg, it is possible that the behavior would change > > potentially in the future. > > Since now every guest has its own idregs, for every guest, the idregs > > should be read from kvm_arm_read_id_reg instead of > > read_sanitised_ftr_reg. > > The point is, for trap_dbgdidr, we should read AA64DFR0/AA64PFR0 from > > host or the VM-scope? > > Ok. I was just double checking whether it changes the behavior now itself or > not as we claim no functional changes in this series. As far as host vs VM > scope, I am not sure as well. From a quick look through the history of debug > support, couldn’t find anything that mandates host values though. > > Thanks, > Shameer > Thanks for the investigation. Let's keep it this way now and see if there are any other comments. Jing
