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charset="utf-8" From: Patrick Roy Support for GUEST_MEMFD_FLAG_NO_DIRECT_MAP on arm64 depends on 1) direct map manipulations at 4k granularity being possible, and 2) FEAT_S2FWB. 1) is met whenever the direct map is set up at 4k granularity (e.g. not with huge/gigantic pages) at boottime, as due to ARM's break-before-make semantics, breaking huge mappings into 4k mappings in the direct map is not possible (BBM would require temporary invalidation of the entire huge mapping, even if only a 4k subrange should be zapped, which will probably crash the kernel). However, the current default for rodata_full is true, which forces a 4k direct map. 2) is required to allow KVM to elide cache coherency operations when installing stage 2 page tables, which require the direct map to be entry for the newly mapped memory to be present (which it will not be, as guest_memfd would have removed direct map entries in kvm_gmem_get_pfn()). Cc: Will Deacon Signed-off-by: Patrick Roy Reviewed-by: David Hildenbrand (Arm) Signed-off-by: Nikita Kalyazin --- arch/arm64/include/asm/kvm_host.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm= _host.h index 70cb9cfd760a..fbdd43e7e94e 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -19,6 +19,7 @@ #include #include #include +#include #include #include #include @@ -1682,6 +1683,18 @@ static __always_inline enum fgt_group_id __fgt_reg_t= o_group_id(enum vcpu_sysreg \ p; \ }) +#ifdef CONFIG_KVM_GUEST_MEMFD +static inline bool kvm_arch_gmem_supports_no_direct_map(struct kvm *kvm) +{ + /* + * Without FWB, direct map access is needed in kvm_pgtable_stage2_map(), + * as it calls dcache_clean_inval_poc(). + */ + return can_set_direct_map() && cpus_have_final_cap(ARM64_HAS_STAGE2_FWB); +} +#define kvm_arch_gmem_supports_no_direct_map kvm_arch_gmem_supports_no_dir= ect_map +#endif /* CONFIG_KVM_GUEST_MEMFD */ + =20 long kvm_get_cap_for_kvm_ioctl(unsigned int ioctl, long *ext); =20 --=20 2.50.1