Commit f320bc74 authored by Quentin Perret's avatar Quentin Perret Committed by Marc Zyngier
Browse files

KVM: arm64: Prepare the creation of s1 mappings at EL2 



When memory protection is enabled, the EL2 code needs the ability to
create and manage its own page-table. To do so, introduce a new set of
hypercalls to bootstrap a memory management system at EL2.

This leads to the following boot flow in nVHE Protected mode:

 1. the host allocates memory for the hypervisor very early on, using
    the memblock API;

 2. the host creates a set of stage 1 page-table for EL2, installs the
    EL2 vectors, and issues the __pkvm_init hypercall;

 3. during __pkvm_init, the hypervisor re-creates its stage 1 page-table
    and stores it in the memory pool provided by the host;

 4. the hypervisor then extends its stage 1 mappings to include a
    vmemmap in the EL2 VA space, hence allowing to use the buddy
    allocator introduced in a previous patch;

 5. the hypervisor jumps back in the idmap page, switches from the
    host-provided page-table to the new one, and wraps up its
    initialization by enabling the new allocator, before returning to
    the host.

 6. the host can free the now unused page-table created for EL2, and
    will now need to issue hypercalls to make changes to the EL2 stage 1
    mappings instead of modifying them directly.

Note that for the sake of simplifying the review, this patch focuses on
the hypervisor side of things. In other words, this only implements the
new hypercalls, but does not make use of them from the host yet. The
host-side changes will follow in a subsequent patch.

Credits to Will for __pkvm_init_switch_pgd.

Acked-by: default avatarWill Deacon <will@kernel.org>
Co-authored-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarWill Deacon <will@kernel.org>
Signed-off-by: default avatarQuentin Perret <qperret@google.com>
Signed-off-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210319100146.1149909-18-qperret@google.com
parent 8f4de66e

arch/arm64/include/asm/kvm_asm.h

+4 −0
Original line number Diff line number Diff line
@@ -57,6 +57,10 @@ 
#define __KVM_HOST_SMCCC_FUNC___kvm_get_mdcr_el2		12

#define __KVM_HOST_SMCCC_FUNC___vgic_v3_save_aprs		13

#define __KVM_HOST_SMCCC_FUNC___vgic_v3_restore_aprs		14

#define __KVM_HOST_SMCCC_FUNC___pkvm_init			15

#define __KVM_HOST_SMCCC_FUNC___pkvm_create_mappings		16

#define __KVM_HOST_SMCCC_FUNC___pkvm_create_private_mapping	17

#define __KVM_HOST_SMCCC_FUNC___pkvm_cpu_set_vector		18



#ifndef __ASSEMBLY__

arch/arm64/include/asm/kvm_host.h

+7 −0
Original line number Diff line number Diff line
@@ -770,5 +770,12 @@ bool kvm_arm_vcpu_is_finalized(struct kvm_vcpu *vcpu); 
	(test_bit(KVM_ARM_VCPU_PMU_V3, (vcpu)->arch.features))



int kvm_trng_call(struct kvm_vcpu *vcpu);

#ifdef CONFIG_KVM

extern phys_addr_t hyp_mem_base;

extern phys_addr_t hyp_mem_size;

void __init kvm_hyp_reserve(void);

#else

static inline void kvm_hyp_reserve(void) { }

#endif



#endif /* __ARM64_KVM_HOST_H__ */

arch/arm64/include/asm/kvm_hyp.h

+8 −0
Original line number Diff line number Diff line
@@ -108,4 +108,12 @@ void __noreturn __hyp_do_panic(struct kvm_cpu_context *host_ctxt, u64 spsr, 
			       u64 elr, u64 par);

#endif



#ifdef __KVM_NVHE_HYPERVISOR__

void __pkvm_init_switch_pgd(phys_addr_t phys, unsigned long size,

			    phys_addr_t pgd, void *sp, void *cont_fn);

int __pkvm_init(phys_addr_t phys, unsigned long size, unsigned long nr_cpus,

		unsigned long *per_cpu_base, u32 hyp_va_bits);

void __noreturn __host_enter(struct kvm_cpu_context *host_ctxt);

#endif



#endif /* __ARM64_KVM_HYP_H__ */

arch/arm64/include/asm/kvm_pgtable.h

+2 −0
Original line number Diff line number Diff line
@@ -11,6 +11,8 @@ 
#include <linux/kvm_host.h>

#include <linux/types.h>



#define KVM_PGTABLE_MAX_LEVELS		4U



typedef u64 kvm_pte_t;



/**

arch/arm64/kernel/image-vars.h

+16 −0
Original line number Diff line number Diff line
@@ -115,6 +115,22 @@ KVM_NVHE_ALIAS_HYP(__memcpy, __pi_memcpy); 
KVM_NVHE_ALIAS_HYP(__memset, __pi_memset);

#endif



/* Kernel memory sections */

KVM_NVHE_ALIAS(__start_rodata);

KVM_NVHE_ALIAS(__end_rodata);

KVM_NVHE_ALIAS(__bss_start);

KVM_NVHE_ALIAS(__bss_stop);



/* Hyp memory sections */

KVM_NVHE_ALIAS(__hyp_idmap_text_start);

KVM_NVHE_ALIAS(__hyp_idmap_text_end);

KVM_NVHE_ALIAS(__hyp_text_start);

KVM_NVHE_ALIAS(__hyp_text_end);

KVM_NVHE_ALIAS(__hyp_bss_start);

KVM_NVHE_ALIAS(__hyp_bss_end);

KVM_NVHE_ALIAS(__hyp_rodata_start);

KVM_NVHE_ALIAS(__hyp_rodata_end);



#endif /* CONFIG_KVM */



#endif /* __ARM64_KERNEL_IMAGE_VARS_H */