From: Ackerley Tng <[email protected]> Add CAP to enumerate supported SET_MEMORY_ATTRIBUTES2 flags, so userspace can find out which flags are supported when sending the KVM_SET_MEMORY_ATTRIBUTES2 ioctl to a guest_memfd.
Add a parameter for_cap to support enumeration of supported flags irrespective of attribute being set. These flags are only supported by guest_memfd, hence, if vm_memory_attributes is enabled, return 0 - no flags are supported when KVM_SET_MEMORY_ATTRIBUTES2 is sent to a VM fd. Signed-off-by: Ackerley Tng <[email protected]> --- Documentation/virt/kvm/api.rst | 3 +++ arch/x86/kvm/x86.c | 5 +++-- include/linux/kvm_host.h | 11 ++++++++++- include/uapi/linux/kvm.h | 1 + virt/kvm/guest_memfd.c | 6 ++++-- virt/kvm/kvm_main.c | 5 +++++ 6 files changed, 26 insertions(+), 5 deletions(-) diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index aaa4a82f0b75d..38938243c2dfd 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6685,6 +6685,9 @@ guarantees are made on offset ranges that do not have memory allocated and range [0x0000, 0x3000) was set to shared, the content mode would apply to only to offset ranges [0x0000, 0x1000) and [0x2000, 0x3000). +The supported content modes can be queried using +``KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS``. + See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`. .. _kvm_run: diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 296ed3b8ace6c..92709735613d5 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -14195,7 +14195,8 @@ void kvm_arch_gmem_invalidate(kvm_pfn_t start, kvm_pfn_t end) } #endif -u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) +u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private, + bool for_cap) { if (!kvm) { return KVM_SET_MEMORY_ATTRIBUTES2_ZERO | @@ -14227,7 +14228,7 @@ u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) * shared, memory contents for pages that had already * been faulted could be zeroed. */ - if (to_private && !kvm->arch.pre_fault_allowed) + if (for_cap || (to_private && !kvm->arch.pre_fault_allowed)) supported |= KVM_SET_MEMORY_ATTRIBUTES2_PRESERVE; return supported; diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 458bad0083c37..13d126dde32f1 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -742,7 +742,8 @@ static inline u64 kvm_gmem_get_supported_flags(struct kvm *kvm) return flags; } -u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private); +u64 kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private, + bool for_cap); int kvm_gmem_apply_content_mode_zero(struct inode *inode, pgoff_t start, pgoff_t end); int kvm_arch_gmem_apply_content_mode_zero(struct kvm *kvm, struct inode *inode, @@ -2551,6 +2552,14 @@ static inline u64 kvm_supported_mem_attributes(struct kvm *kvm) return 0; } +static inline u64 kvm_supported_set_mem_attributes2_flags(struct kvm *kvm) +{ + if (!IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)) + return 0; + + return kvm_arch_gmem_supported_content_modes(kvm, false, true); +} + typedef unsigned long (kvm_get_memory_attributes_t)(struct kvm *kvm, gfn_t gfn); DECLARE_STATIC_CALL(__kvm_get_memory_attributes, kvm_get_memory_attributes_t); diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index c7cc6c22c2023..c0d465a5577da 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -997,6 +997,7 @@ struct kvm_enable_cap { #define KVM_CAP_S390_KEYOP 247 #define KVM_CAP_S390_VSIE_ESAMODE 248 #define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 249 +#define KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS 250 struct kvm_irq_routing_irqchip { __u32 irqchip; diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c index 5c1db67e6fd35..071bf636ba5c0 100644 --- a/virt/kvm/guest_memfd.c +++ b/virt/kvm/guest_memfd.c @@ -693,7 +693,8 @@ static void kvm_gmem_invalidate(struct inode *inode, pgoff_t start, pgoff_t end) static void kvm_gmem_invalidate(struct inode *inode, pgoff_t start, pgoff_t end) {} #endif -u64 __weak kvm_arch_gmem_supported_content_modes(struct kvm *kvm, bool to_private) +u64 __weak kvm_arch_gmem_supported_content_modes(struct kvm *kvm, + bool to_private, bool for_cap) { /* Architectures must override with supported modes. */ return 0; @@ -709,7 +710,8 @@ static bool kvm_gmem_content_mode_is_supported(struct kvm *kvm, if (content_mode == KVM_SET_MEMORY_ATTRIBUTES2_ZERO && to_private) return false; - return kvm_arch_gmem_supported_content_modes(kvm, to_private) & content_mode; + return kvm_arch_gmem_supported_content_modes(kvm, to_private, false) & + content_mode; } int kvm_gmem_apply_content_mode_zero(struct inode *inode, pgoff_t start, diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 3bf212fd99193..9fa6ecebab939 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4979,6 +4979,11 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) return 0; return kvm_supported_mem_attributes(kvm); + case KVM_CAP_MEMORY_ATTRIBUTES2_FLAGS: + if (vm_memory_attributes) + return 0; + + return kvm_supported_set_mem_attributes2_flags(kvm); #endif default: break; -- 2.54.0.545.g6539524ca2-goog
