Re: [PATCH v6 08/12] KVM: arm64: Add handlers for protected VM System Registers

[Andrew Jones <drjones@redhat.com>]

On Wed, Sep 22, 2021 at 01:47:00PM +0100, Fuad Tabba wrote:
> Add system register handlers for protected VMs. These cover Sys64
> registers (including feature id registers), and debug.
> 
> No functional change intended as these are not hooked in yet to
> the guest exit handlers introduced earlier. So when trapping is
> triggered, the exit handlers let the host handle it, as before.
> 
> Signed-off-by: Fuad Tabba <tabba@google.com>
> ---
>  arch/arm64/include/asm/kvm_fixed_config.h  | 195 ++++++++
>  arch/arm64/include/asm/kvm_hyp.h           |   5 +
>  arch/arm64/kvm/arm.c                       |   5 +
>  arch/arm64/kvm/hyp/include/nvhe/sys_regs.h |  28 ++
>  arch/arm64/kvm/hyp/nvhe/Makefile           |   2 +-
>  arch/arm64/kvm/hyp/nvhe/sys_regs.c         | 492 +++++++++++++++++++++
>  6 files changed, 726 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/include/asm/kvm_fixed_config.h
>  create mode 100644 arch/arm64/kvm/hyp/include/nvhe/sys_regs.h
>  create mode 100644 arch/arm64/kvm/hyp/nvhe/sys_regs.c
> 
> diff --git a/arch/arm64/include/asm/kvm_fixed_config.h b/arch/arm64/include/asm/kvm_fixed_config.h
> new file mode 100644
> index 000000000000..0ed06923f7e9
> --- /dev/null
> +++ b/arch/arm64/include/asm/kvm_fixed_config.h
> @@ -0,0 +1,195 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 Google LLC
> + * Author: Fuad Tabba <tabba@google.com>
> + */
> +
> +#ifndef __ARM64_KVM_FIXED_CONFIG_H__
> +#define __ARM64_KVM_FIXED_CONFIG_H__
> +
> +#include <asm/sysreg.h>
> +
> +/*
> + * This file contains definitions for features to be allowed or restricted for
> + * guest virtual machines, depending on the mode KVM is running in and on the
> + * type of guest that is running.
> + *
> + * The ALLOW masks represent a bitmask of feature fields that are allowed
> + * without any restrictions as long as they are supported by the system.
> + *
> + * The RESTRICT_UNSIGNED masks, if present, represent unsigned fields for
> + * features that are restricted to support at most the specified feature.
> + *
> + * If a feature field is not present in either, than it is not supported.
> + *
> + * The approach taken for protected VMs is to allow features that are:
> + * - Needed by common Linux distributions (e.g., floating point)
> + * - Trivial to support, e.g., supporting the feature does not introduce or
> + * require tracking of additional state in KVM
> + * - Cannot be trapped or prevent the guest from using anyway
> + */
> +
> +/*
> + * Allow for protected VMs:
> + * - Floating-point and Advanced SIMD
> + * - Data Independent Timing
> + */
> +#define PVM_ID_AA64PFR0_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64PFR0_FP) | \
> +	ARM64_FEATURE_MASK(ID_AA64PFR0_ASIMD) | \
> +	ARM64_FEATURE_MASK(ID_AA64PFR0_DIT) \
> +	)
> +
> +/*
> + * Restrict to the following *unsigned* features for protected VMs:
> + * - AArch64 guests only (no support for AArch32 guests):
> + *	AArch32 adds complexity in trap handling, emulation, condition codes,
> + *	etc...
> + * - RAS (v1)
> + *	Supported by KVM
> + */
> +#define PVM_ID_AA64PFR0_RESTRICT_UNSIGNED (\
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL0), ID_AA64PFR0_ELx_64BIT_ONLY) | \
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1), ID_AA64PFR0_ELx_64BIT_ONLY) | \
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL2), ID_AA64PFR0_ELx_64BIT_ONLY) | \
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_EL3), ID_AA64PFR0_ELx_64BIT_ONLY) | \
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_RAS), ID_AA64PFR0_RAS_V1) \
> +	)
> +
> +/*
> + * Allow for protected VMs:
> + * - Branch Target Identification
> + * - Speculative Store Bypassing
> + */
> +#define PVM_ID_AA64PFR1_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64PFR1_BT) | \
> +	ARM64_FEATURE_MASK(ID_AA64PFR1_SSBS) \
> +	)
> +
> +/*
> + * Allow for protected VMs:
> + * - Mixed-endian
> + * - Distinction between Secure and Non-secure Memory
> + * - Mixed-endian at EL0 only
> + * - Non-context synchronizing exception entry and exit
> + */
> +#define PVM_ID_AA64MMFR0_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64MMFR0_BIGENDEL) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR0_SNSMEM) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR0_BIGENDEL0) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR0_EXS) \
> +	)
> +
> +/*
> + * Restrict to the following *unsigned* features for protected VMs:
> + * - 40-bit IPA
> + * - 16-bit ASID
> + */
> +#define PVM_ID_AA64MMFR0_RESTRICT_UNSIGNED (\
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64MMFR0_PARANGE), ID_AA64MMFR0_PARANGE_40) | \
> +	FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64MMFR0_ASID), ID_AA64MMFR0_ASID_16) \
> +	)
> +
> +/*
> + * Allow for protected VMs:
> + * - Hardware translation table updates to Access flag and Dirty state
> + * - Number of VMID bits from CPU
> + * - Hierarchical Permission Disables
> + * - Privileged Access Never
> + * - SError interrupt exceptions from speculative reads
> + * - Enhanced Translation Synchronization
> + */
> +#define PVM_ID_AA64MMFR1_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_HADBS) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_VMIDBITS) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_HPD) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_PAN) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_SPECSEI) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR1_ETS) \
> +	)
> +
> +/*
> + * Allow for protected VMs:
> + * - Common not Private translations
> + * - User Access Override
> + * - IESB bit in the SCTLR_ELx registers
> + * - Unaligned single-copy atomicity and atomic functions
> + * - ESR_ELx.EC value on an exception by read access to feature ID space
> + * - TTL field in address operations.
> + * - Break-before-make sequences when changing translation block size
> + * - E0PDx mechanism
> + */
> +#define PVM_ID_AA64MMFR2_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_CNP) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_UAO) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_IESB) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_AT) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_IDS) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_TTL) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_BBM) | \
> +	ARM64_FEATURE_MASK(ID_AA64MMFR2_E0PD) \
> +	)
> +
> +/*
> + * No support for Scalable Vectors for protected VMs:
> + *	Requires additional support from KVM, e.g., context-switching and
> + *	trapping at EL2
> + */
> +#define PVM_ID_AA64ZFR0_ALLOW (0ULL)
> +
> +/*
> + * No support for debug, including breakpoints, and watchpoints for protected
> + * VMs:
> + *	The Arm architecture mandates support for at least the Armv8 debug
> + *	architecture, which would include at least 2 hardware breakpoints and
> + *	watchpoints. Providing that support to protected guests adds
> + *	considerable state and complexity. Therefore, the reserved value of 0 is
> + *	used for debug-related fields.
> + */
> +#define PVM_ID_AA64DFR0_ALLOW (0ULL)
> +#define PVM_ID_AA64DFR1_ALLOW (0ULL)
> +
> +/*
> + * No support for implementation defined features.
> + */
> +#define PVM_ID_AA64AFR0_ALLOW (0ULL)
> +#define PVM_ID_AA64AFR1_ALLOW (0ULL)
> +
> +/*
> + * No restrictions on instructions implemented in AArch64.
> + */
> +#define PVM_ID_AA64ISAR0_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_AES) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_SHA1) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_SHA2) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_CRC32) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_ATOMICS) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_RDM) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_SHA3) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_SM3) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_SM4) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_DP) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_FHM) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_TS) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_TLB) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR0_RNDR) \
> +	)
> +
> +#define PVM_ID_AA64ISAR1_ALLOW (\
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_DPB) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_APA) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_API) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_JSCVT) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_FCMA) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_LRCPC) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_GPA) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_GPI) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_FRINTTS) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_SB) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_SPECRES) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_BF16) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_DGH) | \
> +	ARM64_FEATURE_MASK(ID_AA64ISAR1_I8MM) \
> +	)
> +
> +#endif /* __ARM64_KVM_FIXED_CONFIG_H__ */
> diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> index 657d0c94cf82..5afd14ab15b9 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -115,7 +115,12 @@ int __pkvm_init(phys_addr_t phys, unsigned long size, unsigned long nr_cpus,
>  void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);
>  #endif
>  
> +extern u64 kvm_nvhe_sym(id_aa64pfr0_el1_sys_val);
> +extern u64 kvm_nvhe_sym(id_aa64pfr1_el1_sys_val);
> +extern u64 kvm_nvhe_sym(id_aa64isar0_el1_sys_val);
> +extern u64 kvm_nvhe_sym(id_aa64isar1_el1_sys_val);
>  extern u64 kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val);
>  extern u64 kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val);
> +extern u64 kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val);
>  
>  #endif /* __ARM64_KVM_HYP_H__ */
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index fe102cd2e518..6aa7b0c5bf21 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -1802,8 +1802,13 @@ static int kvm_hyp_init_protection(u32 hyp_va_bits)
>  	void *addr = phys_to_virt(hyp_mem_base);
>  	int ret;
>  
> +	kvm_nvhe_sym(id_aa64pfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64PFR0_EL1);
> +	kvm_nvhe_sym(id_aa64pfr1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1);
> +	kvm_nvhe_sym(id_aa64isar0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64ISAR0_EL1);
> +	kvm_nvhe_sym(id_aa64isar1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64ISAR1_EL1);
>  	kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
>  	kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
> +	kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR2_EL1);
>  
>  	ret = create_hyp_mappings(addr, addr + hyp_mem_size, PAGE_HYP);
>  	if (ret)
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/sys_regs.h b/arch/arm64/kvm/hyp/include/nvhe/sys_regs.h
> new file mode 100644
> index 000000000000..0865163d363c
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/include/nvhe/sys_regs.h
> @@ -0,0 +1,28 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright (C) 2021 Google LLC
> + * Author: Fuad Tabba <tabba@google.com>
> + */
> +
> +#ifndef __ARM64_KVM_NVHE_SYS_REGS_H__
> +#define __ARM64_KVM_NVHE_SYS_REGS_H__
> +
> +#include <asm/kvm_host.h>
> +
> +u64 get_pvm_id_aa64pfr0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64pfr1(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64zfr0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64dfr0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64dfr1(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64afr0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64afr1(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64isar0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64isar1(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64mmfr0(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64mmfr1(const struct kvm_vcpu *vcpu);
> +u64 get_pvm_id_aa64mmfr2(const struct kvm_vcpu *vcpu);
> +
> +bool kvm_handle_pvm_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code);
> +void __inject_undef64(struct kvm_vcpu *vcpu);
> +
> +#endif /* __ARM64_KVM_NVHE_SYS_REGS_H__ */
> diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
> index 8d741f71377f..0bbe37a18d5d 100644
> --- a/arch/arm64/kvm/hyp/nvhe/Makefile
> +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
> @@ -14,7 +14,7 @@ lib-objs := $(addprefix ../../../lib/, $(lib-objs))
>  
>  obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
>  	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o page_alloc.o \
> -	 cache.o setup.o mm.o mem_protect.o
> +	 cache.o setup.o mm.o mem_protect.o sys_regs.o
>  obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
>  	 ../fpsimd.o ../hyp-entry.o ../exception.o ../pgtable.o
>  obj-y += $(lib-objs)
> diff --git a/arch/arm64/kvm/hyp/nvhe/sys_regs.c b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
> new file mode 100644
> index 000000000000..ef8456c54b18
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/nvhe/sys_regs.c
> @@ -0,0 +1,492 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2021 Google LLC
> + * Author: Fuad Tabba <tabba@google.com>
> + */
> +
> +#include <asm/kvm_asm.h>
> +#include <asm/kvm_fixed_config.h>
> +#include <asm/kvm_mmu.h>
> +
> +#include <hyp/adjust_pc.h>
> +
> +#include "../../sys_regs.h"
> +
> +/*
> + * Copies of the host's CPU features registers holding sanitized values at hyp.
> + */
> +u64 id_aa64pfr0_el1_sys_val;
> +u64 id_aa64pfr1_el1_sys_val;
> +u64 id_aa64isar0_el1_sys_val;
> +u64 id_aa64isar1_el1_sys_val;
> +u64 id_aa64mmfr2_el1_sys_val;
> +
> +static inline void inject_undef64(struct kvm_vcpu *vcpu)
> +{
> +	u32 esr = (ESR_ELx_EC_UNKNOWN << ESR_ELx_EC_SHIFT);
> +
> +	vcpu->arch.flags |= (KVM_ARM64_EXCEPT_AA64_EL1 |
> +			     KVM_ARM64_EXCEPT_AA64_ELx_SYNC |
> +			     KVM_ARM64_PENDING_EXCEPTION);
> +
> +	__kvm_adjust_pc(vcpu);
> +
> +	write_sysreg_el1(esr, SYS_ESR);
> +	write_sysreg_el1(read_sysreg_el2(SYS_ELR), SYS_ELR);
> +}
> +
> +/*
> + * Inject an unknown/undefined exception to an AArch64 guest while most of its
> + * sysregs are live.
> + */
> +void __inject_undef64(struct kvm_vcpu *vcpu)
> +{
> +	*vcpu_pc(vcpu) = read_sysreg_el2(SYS_ELR);
> +	*vcpu_cpsr(vcpu) = read_sysreg_el2(SYS_SPSR);
> +
> +	inject_undef64(vcpu);
> +
> +	write_sysreg_el2(*vcpu_pc(vcpu), SYS_ELR);
> +	write_sysreg_el2(*vcpu_cpsr(vcpu), SYS_SPSR);
> +}
> +
> +/*
> + * Accessor for undefined accesses.
> + */
> +static bool undef_access(struct kvm_vcpu *vcpu,
> +			 struct sys_reg_params *p,
> +			 const struct sys_reg_desc *r)
> +{
> +	__inject_undef64(vcpu);
> +	return false;
> +}
> +
> +/*
> + * Returns the restricted features values of the feature register based on the
> + * limitations in restrict_fields.
> + * A feature id field value of 0b0000 does not impose any restrictions.
> + * Note: Use only for unsigned feature field values.
> + */
> +static u64 get_restricted_features_unsigned(u64 sys_reg_val,
> +					    u64 restrict_fields)
> +{
> +	u64 value = 0UL;
> +	u64 mask = GENMASK_ULL(ARM64_FEATURE_FIELD_BITS - 1, 0);
> +
> +	/*
> +	 * According to the Arm Architecture Reference Manual, feature fields
> +	 * use increasing values to indicate increases in functionality.
> +	 * Iterate over the restricted feature fields and calculate the minimum
> +	 * unsigned value between the one supported by the system, and what the
> +	 * value is being restricted to.
> +	 */
> +	while (sys_reg_val && restrict_fields) {
> +		value |= min(sys_reg_val & mask, restrict_fields & mask);
> +		sys_reg_val &= ~mask;
> +		restrict_fields &= ~mask;
> +		mask <<= ARM64_FEATURE_FIELD_BITS;
> +	}
> +
> +	return value;
> +}
> +
> +/*
> + * Functions that return the value of feature id registers for protected VMs
> + * based on allowed features, system features, and KVM support.
> + */
> +
> +u64 get_pvm_id_aa64pfr0(const struct kvm_vcpu *vcpu)
> +{
> +	const struct kvm *kvm = (const struct kvm *)kern_hyp_va(vcpu->kvm);
> +	u64 set_mask = 0;
> +	u64 allow_mask = PVM_ID_AA64PFR0_ALLOW;
> +
> +	if (!vcpu_has_sve(vcpu))
> +		allow_mask &= ~ARM64_FEATURE_MASK(ID_AA64PFR0_SVE);
> +
> +	set_mask |= get_restricted_features_unsigned(id_aa64pfr0_el1_sys_val,
> +		PVM_ID_AA64PFR0_RESTRICT_UNSIGNED);
> +
> +	/* Spectre and Meltdown mitigation in KVM */
> +	set_mask |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_CSV2),
> +			       (u64)kvm->arch.pfr0_csv2);
> +	set_mask |= FIELD_PREP(ARM64_FEATURE_MASK(ID_AA64PFR0_CSV3),
> +			       (u64)kvm->arch.pfr0_csv3);
> +
> +	return (id_aa64pfr0_el1_sys_val & allow_mask) | set_mask;
> +}
> +
> +u64 get_pvm_id_aa64pfr1(const struct kvm_vcpu *vcpu)
> +{
> +	const struct kvm *kvm = (const struct kvm *)kern_hyp_va(vcpu->kvm);
> +	u64 allow_mask = PVM_ID_AA64PFR1_ALLOW;
> +
> +	if (!kvm_has_mte(kvm))
> +		allow_mask &= ~ARM64_FEATURE_MASK(ID_AA64PFR1_MTE);
> +
> +	return id_aa64pfr1_el1_sys_val & allow_mask;
> +}
> +
> +u64 get_pvm_id_aa64zfr0(const struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * No support for Scalable Vectors, therefore, hyp has no sanitized
> +	 * copy of the feature id register.
> +	 */
> +	BUILD_BUG_ON(PVM_ID_AA64ZFR0_ALLOW != 0ULL);
> +	return 0;
> +}
> +
> +u64 get_pvm_id_aa64dfr0(const struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * No support for debug, including breakpoints, and watchpoints,
> +	 * therefore, pKVM has no sanitized copy of the feature id register.
> +	 */
> +	BUILD_BUG_ON(PVM_ID_AA64DFR0_ALLOW != 0ULL);
> +	return 0;
> +}
> +
> +u64 get_pvm_id_aa64dfr1(const struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * No support for debug, therefore, hyp has no sanitized copy of the
> +	 * feature id register.
> +	 */
> +	BUILD_BUG_ON(PVM_ID_AA64DFR1_ALLOW != 0ULL);
> +	return 0;
> +}
> +
> +u64 get_pvm_id_aa64afr0(const struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * No support for implementation defined features, therefore, hyp has no
> +	 * sanitized copy of the feature id register.
> +	 */
> +	BUILD_BUG_ON(PVM_ID_AA64AFR0_ALLOW != 0ULL);
> +	return 0;
> +}
> +
> +u64 get_pvm_id_aa64afr1(const struct kvm_vcpu *vcpu)
> +{
> +	/*
> +	 * No support for implementation defined features, therefore, hyp has no
> +	 * sanitized copy of the feature id register.
> +	 */
> +	BUILD_BUG_ON(PVM_ID_AA64AFR1_ALLOW != 0ULL);
> +	return 0;
> +}

Reading the same function five times make me wonder if a generator macro
wouldn't be better for these.

> +
> +u64 get_pvm_id_aa64isar0(const struct kvm_vcpu *vcpu)
> +{
> +	return id_aa64isar0_el1_sys_val & PVM_ID_AA64ISAR0_ALLOW;
> +}
> +
> +u64 get_pvm_id_aa64isar1(const struct kvm_vcpu *vcpu)
> +{
> +	u64 allow_mask = PVM_ID_AA64ISAR1_ALLOW;
> +
> +	if (!vcpu_has_ptrauth(vcpu))
> +		allow_mask &= ~(ARM64_FEATURE_MASK(ID_AA64ISAR1_APA) |
> +				ARM64_FEATURE_MASK(ID_AA64ISAR1_API) |
> +				ARM64_FEATURE_MASK(ID_AA64ISAR1_GPA) |
> +				ARM64_FEATURE_MASK(ID_AA64ISAR1_GPI));
> +
> +	return id_aa64isar1_el1_sys_val & allow_mask;
> +}
> +
> +u64 get_pvm_id_aa64mmfr0(const struct kvm_vcpu *vcpu)
> +{
> +	u64 set_mask;
> +
> +	set_mask = get_restricted_features_unsigned(id_aa64mmfr0_el1_sys_val,
> +		PVM_ID_AA64MMFR0_RESTRICT_UNSIGNED);
> +
> +	return (id_aa64mmfr0_el1_sys_val & PVM_ID_AA64MMFR0_ALLOW) | set_mask;
> +}
> +
> +u64 get_pvm_id_aa64mmfr1(const struct kvm_vcpu *vcpu)
> +{
> +	return id_aa64mmfr1_el1_sys_val & PVM_ID_AA64MMFR1_ALLOW;
> +}
> +
> +u64 get_pvm_id_aa64mmfr2(const struct kvm_vcpu *vcpu)
> +{
> +	return id_aa64mmfr2_el1_sys_val & PVM_ID_AA64MMFR2_ALLOW;
> +}
> +
> +/* Read a sanitized cpufeature ID register by its sys_reg_desc. */
> +static u64 read_id_reg(const struct kvm_vcpu *vcpu,
> +		       struct sys_reg_desc const *r)
> +{
> +	u32 id = reg_to_encoding(r);
> +
> +	switch (id) {
> +	case SYS_ID_AA64PFR0_EL1:
> +		return get_pvm_id_aa64pfr0(vcpu);
> +	case SYS_ID_AA64PFR1_EL1:
> +		return get_pvm_id_aa64pfr1(vcpu);
> +	case SYS_ID_AA64ZFR0_EL1:
> +		return get_pvm_id_aa64zfr0(vcpu);
> +	case SYS_ID_AA64DFR0_EL1:
> +		return get_pvm_id_aa64dfr0(vcpu);
> +	case SYS_ID_AA64DFR1_EL1:
> +		return get_pvm_id_aa64dfr1(vcpu);
> +	case SYS_ID_AA64AFR0_EL1:
> +		return get_pvm_id_aa64afr0(vcpu);
> +	case SYS_ID_AA64AFR1_EL1:
> +		return get_pvm_id_aa64afr1(vcpu);
> +	case SYS_ID_AA64ISAR0_EL1:
> +		return get_pvm_id_aa64isar0(vcpu);
> +	case SYS_ID_AA64ISAR1_EL1:
> +		return get_pvm_id_aa64isar1(vcpu);
> +	case SYS_ID_AA64MMFR0_EL1:
> +		return get_pvm_id_aa64mmfr0(vcpu);
> +	case SYS_ID_AA64MMFR1_EL1:
> +		return get_pvm_id_aa64mmfr1(vcpu);
> +	case SYS_ID_AA64MMFR2_EL1:
> +		return get_pvm_id_aa64mmfr2(vcpu);
> +	default:
> +		/*
> +		 * Should never happen because all cases are covered in
> +		 * pvm_sys_reg_descs[] below.

I'd drop the 'below' word. It's not overly helpful and since code gets
moved it can go out of date.

> +		 */
> +		WARN_ON(1);

The above cases could also be generated by a macro. And I wonder if we can
come up with something that makes sure these separate lists stay
consistent with macros and build bugs in order to better avoid these
"should never happen" situations.

> +		break;
> +	}
> +
> +	return 0;
> +}
> +
> +/*
> + * Accessor for AArch32 feature id registers.
> + *
> + * The value of these registers is "unknown" according to the spec if AArch32
> + * isn't supported.
> + */
> +static bool pvm_access_id_aarch32(struct kvm_vcpu *vcpu,
> +				  struct sys_reg_params *p,
> +				  const struct sys_reg_desc *r)
> +{
> +	if (p->is_write)
> +		return undef_access(vcpu, p, r);
> +
> +	/*
> +	 * No support for AArch32 guests, therefore, pKVM has no sanitized copy
> +	 * of AArch32 feature id registers.
> +	 */
> +	BUILD_BUG_ON(FIELD_GET(ARM64_FEATURE_MASK(ID_AA64PFR0_EL1),
> +		     PVM_ID_AA64PFR0_RESTRICT_UNSIGNED) > ID_AA64PFR0_ELx_64BIT_ONLY);
> +
> +	/* Use 0 for architecturally "unknown" values. */
> +	p->regval = 0;
> +	return true;
> +}
> +
> +/*
> + * Accessor for AArch64 feature id registers.
> + *
> + * If access is allowed, set the regval to the protected VM's view of the
> + * register and return true.
> + * Otherwise, inject an undefined exception and return false.
> + */
> +static bool pvm_access_id_aarch64(struct kvm_vcpu *vcpu,
> +				  struct sys_reg_params *p,
> +				  const struct sys_reg_desc *r)
> +{
> +	if (p->is_write)
> +		return undef_access(vcpu, p, r);
> +
> +	p->regval = read_id_reg(vcpu, r);
> +	return true;
> +}
> +
> +/* Mark the specified system register as an AArch32 feature id register. */
> +#define AARCH32(REG) { SYS_DESC(REG), .access = pvm_access_id_aarch32 }
> +
> +/* Mark the specified system register as an AArch64 feature id register. */
> +#define AARCH64(REG) { SYS_DESC(REG), .access = pvm_access_id_aarch64 }
> +
> +/* Mark the specified system register as not being handled in hyp. */
> +#define HOST_HANDLED(REG) { SYS_DESC(REG), .access = NULL }
> +
> +/*
> + * Architected system registers.
> + * Important: Must be sorted ascending by Op0, Op1, CRn, CRm, Op2
> + *
> + * NOTE: Anything not explicitly listed here is *restricted by default*, i.e.,
> + * it will lead to injecting an exception into the guest.
> + */
> +static const struct sys_reg_desc pvm_sys_reg_descs[] = {
> +	/* Cache maintenance by set/way operations are restricted. */
> +
> +	/* Debug and Trace Registers are restricted. */
> +
> +	/* AArch64 mappings of the AArch32 ID registers */
> +	/* CRm=1 */
> +	AARCH32(SYS_ID_PFR0_EL1),
> +	AARCH32(SYS_ID_PFR1_EL1),
> +	AARCH32(SYS_ID_DFR0_EL1),
> +	AARCH32(SYS_ID_AFR0_EL1),
> +	AARCH32(SYS_ID_MMFR0_EL1),
> +	AARCH32(SYS_ID_MMFR1_EL1),
> +	AARCH32(SYS_ID_MMFR2_EL1),
> +	AARCH32(SYS_ID_MMFR3_EL1),
> +
> +	/* CRm=2 */
> +	AARCH32(SYS_ID_ISAR0_EL1),
> +	AARCH32(SYS_ID_ISAR1_EL1),
> +	AARCH32(SYS_ID_ISAR2_EL1),
> +	AARCH32(SYS_ID_ISAR3_EL1),
> +	AARCH32(SYS_ID_ISAR4_EL1),
> +	AARCH32(SYS_ID_ISAR5_EL1),
> +	AARCH32(SYS_ID_MMFR4_EL1),
> +	AARCH32(SYS_ID_ISAR6_EL1),
> +
> +	/* CRm=3 */
> +	AARCH32(SYS_MVFR0_EL1),
> +	AARCH32(SYS_MVFR1_EL1),
> +	AARCH32(SYS_MVFR2_EL1),
> +	AARCH32(SYS_ID_PFR2_EL1),
> +	AARCH32(SYS_ID_DFR1_EL1),
> +	AARCH32(SYS_ID_MMFR5_EL1),
> +
> +	/* AArch64 ID registers */
> +	/* CRm=4 */
> +	AARCH64(SYS_ID_AA64PFR0_EL1),
> +	AARCH64(SYS_ID_AA64PFR1_EL1),
> +	AARCH64(SYS_ID_AA64ZFR0_EL1),
> +	AARCH64(SYS_ID_AA64DFR0_EL1),
> +	AARCH64(SYS_ID_AA64DFR1_EL1),
> +	AARCH64(SYS_ID_AA64AFR0_EL1),
> +	AARCH64(SYS_ID_AA64AFR1_EL1),
> +	AARCH64(SYS_ID_AA64ISAR0_EL1),
> +	AARCH64(SYS_ID_AA64ISAR1_EL1),
> +	AARCH64(SYS_ID_AA64MMFR0_EL1),
> +	AARCH64(SYS_ID_AA64MMFR1_EL1),
> +	AARCH64(SYS_ID_AA64MMFR2_EL1),
> +
> +	HOST_HANDLED(SYS_SCTLR_EL1),
> +	HOST_HANDLED(SYS_ACTLR_EL1),
> +	HOST_HANDLED(SYS_CPACR_EL1),
> +
> +	HOST_HANDLED(SYS_RGSR_EL1),
> +	HOST_HANDLED(SYS_GCR_EL1),
> +
> +	/* Scalable Vector Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_TTBR0_EL1),
> +	HOST_HANDLED(SYS_TTBR1_EL1),
> +	HOST_HANDLED(SYS_TCR_EL1),
> +
> +	HOST_HANDLED(SYS_APIAKEYLO_EL1),
> +	HOST_HANDLED(SYS_APIAKEYHI_EL1),
> +	HOST_HANDLED(SYS_APIBKEYLO_EL1),
> +	HOST_HANDLED(SYS_APIBKEYHI_EL1),
> +	HOST_HANDLED(SYS_APDAKEYLO_EL1),
> +	HOST_HANDLED(SYS_APDAKEYHI_EL1),
> +	HOST_HANDLED(SYS_APDBKEYLO_EL1),
> +	HOST_HANDLED(SYS_APDBKEYHI_EL1),
> +	HOST_HANDLED(SYS_APGAKEYLO_EL1),
> +	HOST_HANDLED(SYS_APGAKEYHI_EL1),
> +
> +	HOST_HANDLED(SYS_AFSR0_EL1),
> +	HOST_HANDLED(SYS_AFSR1_EL1),
> +	HOST_HANDLED(SYS_ESR_EL1),
> +
> +	HOST_HANDLED(SYS_ERRIDR_EL1),
> +	HOST_HANDLED(SYS_ERRSELR_EL1),
> +	HOST_HANDLED(SYS_ERXFR_EL1),
> +	HOST_HANDLED(SYS_ERXCTLR_EL1),
> +	HOST_HANDLED(SYS_ERXSTATUS_EL1),
> +	HOST_HANDLED(SYS_ERXADDR_EL1),
> +	HOST_HANDLED(SYS_ERXMISC0_EL1),
> +	HOST_HANDLED(SYS_ERXMISC1_EL1),
> +
> +	HOST_HANDLED(SYS_TFSR_EL1),
> +	HOST_HANDLED(SYS_TFSRE0_EL1),
> +
> +	HOST_HANDLED(SYS_FAR_EL1),
> +	HOST_HANDLED(SYS_PAR_EL1),
> +
> +	/* Performance Monitoring Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_MAIR_EL1),
> +	HOST_HANDLED(SYS_AMAIR_EL1),
> +
> +	/* Limited Ordering Regions Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_VBAR_EL1),
> +	HOST_HANDLED(SYS_DISR_EL1),
> +
> +	/* GIC CPU Interface registers are restricted. */
> +
> +	HOST_HANDLED(SYS_CONTEXTIDR_EL1),
> +	HOST_HANDLED(SYS_TPIDR_EL1),
> +
> +	HOST_HANDLED(SYS_SCXTNUM_EL1),
> +
> +	HOST_HANDLED(SYS_CNTKCTL_EL1),
> +
> +	HOST_HANDLED(SYS_CCSIDR_EL1),
> +	HOST_HANDLED(SYS_CLIDR_EL1),
> +	HOST_HANDLED(SYS_CSSELR_EL1),
> +	HOST_HANDLED(SYS_CTR_EL0),
> +
> +	/* Performance Monitoring Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_TPIDR_EL0),
> +	HOST_HANDLED(SYS_TPIDRRO_EL0),
> +
> +	HOST_HANDLED(SYS_SCXTNUM_EL0),
> +
> +	/* Activity Monitoring Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_CNTP_TVAL_EL0),
> +	HOST_HANDLED(SYS_CNTP_CTL_EL0),
> +	HOST_HANDLED(SYS_CNTP_CVAL_EL0),
> +
> +	/* Performance Monitoring Registers are restricted. */
> +
> +	HOST_HANDLED(SYS_DACR32_EL2),
> +	HOST_HANDLED(SYS_IFSR32_EL2),
> +	HOST_HANDLED(SYS_FPEXC32_EL2),
> +};
> +
> +/*
> + * Handler for protected VM MSR, MRS or System instruction execution.
> + *
> + * Returns true if the hypervisor has handled the exit, and control should go
> + * back to the guest, or false if it hasn't, to be handled by the host.
> + */
> +bool kvm_handle_pvm_sysreg(struct kvm_vcpu *vcpu, u64 *exit_code)
> +{
> +	const struct sys_reg_desc *r;
> +	struct sys_reg_params params;
> +	unsigned long esr = kvm_vcpu_get_esr(vcpu);
> +	int Rt = kvm_vcpu_sys_get_rt(vcpu);
> +
> +	params = esr_sys64_to_params(esr);
> +	params.regval = vcpu_get_reg(vcpu, Rt);
> +
> +	r = find_reg(&params, pvm_sys_reg_descs, ARRAY_SIZE(pvm_sys_reg_descs));
> +
> +	/* Undefined access (RESTRICTED). */
> +	if (r == NULL) {
> +		__inject_undef64(vcpu);
> +		return true;
> +	}
> +
> +	/* Handled by the host (HOST_HANDLED) */
> +	if (r->access == NULL)
> +		return false;
> +
> +	/* Handled by hyp: skip instruction if instructed to do so. */
> +	if (r->access(vcpu, &params, r))
> +		__kvm_skip_instr(vcpu);
> +
> +	if (!params.is_write)
> +		vcpu_set_reg(vcpu, Rt, params.regval);
> +
> +	return true;
> +}
> -- 
> 2.33.0.464.g1972c5931b-goog
>

Other than the nits and suggestion to try and build in some register list
consistency checks, this looks good to me. I don't know what pKVM
should / should not expose, but I like the approach this takes, so,
FWIW,

Reviewed-by: Andrew Jones <drjones@redhat.com>

Thanks,
drew