Commit d1e54dd0 authored by Fuad Tabba's avatar Fuad Tabba Committed by Paolo Bonzini
Browse files

KVM: x86: Enable KVM_GUEST_MEMFD for all 64-bit builds 



Enable KVM_GUEST_MEMFD for all KVM x86 64-bit builds, i.e. for "default"
VM types when running on 64-bit KVM.  This will allow using guest_memfd
to back non-private memory for all VM shapes, by supporting mmap() on
guest_memfd.

Opportunistically clean up various conditionals that become tautologies
once x86 selects KVM_GUEST_MEMFD more broadly.  Specifically, because
SW protected VMs, SEV, and TDX are all 64-bit only, private memory no
longer needs to take explicit dependencies on KVM_GUEST_MEMFD, because
it is effectively a prerequisite.

Suggested-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarFuad Tabba <tabba@google.com>
Reviewed-by: default avatarXiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Message-ID: <20250729225455.670324-10-seanjc@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 68d18993

arch/x86/include/asm/kvm_host.h

+1 −3
Original line number Diff line number Diff line
@@ -2276,10 +2276,8 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level, 
		       int tdp_max_root_level, int tdp_huge_page_level);





#ifdef CONFIG_KVM_GUEST_MEMFD

#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES

#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)

#else

#define kvm_arch_has_private_mem(kvm) false

#endif



#define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state)

arch/x86/kvm/Kconfig

+4 −8
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ config KVM_X86 
	select KVM_GENERIC_HARDWARE_ENABLING

	select KVM_GENERIC_PRE_FAULT_MEMORY

	select KVM_WERROR if WERROR

	select KVM_GUEST_MEMFD if X86_64



config KVM

	tristate "Kernel-based Virtual Machine (KVM) support"
@@ -79,16 +80,11 @@ config KVM_WERROR 


	  If in doubt, say "N".



config KVM_X86_PRIVATE_MEM

	select KVM_GENERIC_MEMORY_ATTRIBUTES

	select KVM_GUEST_MEMFD

	bool



config KVM_SW_PROTECTED_VM

	bool "Enable support for KVM software-protected VMs"

	depends on EXPERT

	depends on KVM_X86 && X86_64

	select KVM_X86_PRIVATE_MEM

	select KVM_GENERIC_MEMORY_ATTRIBUTES

	help

	  Enable support for KVM software-protected VMs.  Currently, software-

	  protected VMs are purely a development and testing vehicle for
@@ -138,7 +134,7 @@ config KVM_INTEL_TDX 
	bool "Intel Trust Domain Extensions (TDX) support"

	default y

	depends on INTEL_TDX_HOST

	select KVM_X86_PRIVATE_MEM

	select KVM_GENERIC_MEMORY_ATTRIBUTES

	select HAVE_KVM_ARCH_GMEM_POPULATE

	help

	  Provides support for launching Intel Trust Domain Extensions (TDX)
@@ -162,7 +158,7 @@ config KVM_AMD_SEV 
	depends on KVM_AMD && X86_64

	depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)

	select ARCH_HAS_CC_PLATFORM

	select KVM_X86_PRIVATE_MEM

	select KVM_GENERIC_MEMORY_ATTRIBUTES

	select HAVE_KVM_ARCH_GMEM_PREPARE

	select HAVE_KVM_ARCH_GMEM_INVALIDATE

	select HAVE_KVM_ARCH_GMEM_POPULATE

include/linux/kvm_host.h

+2 −7
Original line number Diff line number Diff line
@@ -719,11 +719,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu) 
}

#endif



/*

 * Arch code must define kvm_arch_has_private_mem if support for guest_memfd is

 * enabled.

 */

#if !defined(kvm_arch_has_private_mem) && !IS_ENABLED(CONFIG_KVM_GUEST_MEMFD)

#ifndef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES

static inline bool kvm_arch_has_private_mem(struct kvm *kvm)

{

	return false;
@@ -2505,8 +2501,7 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm, 


static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)

{

	return IS_ENABLED(CONFIG_KVM_GUEST_MEMFD) &&

	       kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;

	return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;

}

#else

static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)

virt/kvm/kvm_main.c

+2 −2
Original line number Diff line number Diff line
@@ -1588,7 +1588,7 @@ static int check_memory_region_flags(struct kvm *kvm, 
{

	u32 valid_flags = KVM_MEM_LOG_DIRTY_PAGES;



	if (kvm_arch_has_private_mem(kvm))

	if (IS_ENABLED(CONFIG_KVM_GUEST_MEMFD))

		valid_flags |= KVM_MEM_GUEST_MEMFD;



	/* Dirty logging private memory is not currently supported. */
@@ -4917,7 +4917,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg) 
#endif

#ifdef CONFIG_KVM_GUEST_MEMFD

	case KVM_CAP_GUEST_MEMFD:

		return !kvm || kvm_arch_has_private_mem(kvm);

		return 1;

#endif

	default:

		break;