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[v8,12/13] KVM: x86: KVM_X86_SW_PROTECTED_VM to support guest_memfd shared memory

Message ID 20250430165655.605595-13-tabba@google.com
State New
Headers show
Series KVM: Mapping guest_memfd backed memory at the host for software protected VMs | expand

Commit Message

Fuad Tabba April 30, 2025, 4:56 p.m. UTC 
The KVM_X86_SW_PROTECTED_VM type is meant for experimentation and does
not have underlying support for protected guests. This makes it a good
candidate for testing mapping shared memory. Therefore, only when the
kconfig option for in-place shared memory is enabled
(KVM_GMEM_SHARED_MEM), mark this type as supporting shared memory.

This means that this memory is considered by guest_memfd to be shared
with the host, which is now able to map and fault in guest_memfd memory
belonging to this VM type.

Signed-off-by: Fuad Tabba <tabba@google.com>
---
 arch/x86/include/asm/kvm_host.h | 5 +++++
 1 file changed, 5 insertions(+)
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Patch

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 709cc2a7ba66..1858dde449c3 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2255,8 +2255,13 @@  void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
 
 #ifdef CONFIG_KVM_GMEM
 #define kvm_arch_supports_gmem(kvm) ((kvm)->arch.supports_gmem)
+
+#define kvm_arch_gmem_supports_shared_mem(kvm)         \
+	(IS_ENABLED(CONFIG_KVM_GMEM_SHARED_MEM) &&      \
+	 ((kvm)->arch.vm_type == KVM_X86_SW_PROTECTED_VM))
 #else
 #define kvm_arch_supports_gmem(kvm) false
+#define kvm_arch_gmem_supports_shared_mem(kvm) false
 #endif
 
 #define kvm_arch_has_readonly_mem(kvm) (!(kvm)->arch.has_protected_state)