Update SEV-SNP implementation to run on upstream kernels

[tylerfanelli]

Modify the SEV-SNP launch implementation to:

• Create VMs with the KVM_X86_SNP_VM type.
• Use KVM guest_memfd for memory regions.
• Use KVM_SET_USER_MEMORY_REGION2.
• Update the sev library dependency to 5.0.0.

With this, libkrun should be able to run on stock Linux kernels with version >= 6.11. Still completing some testing. Once tested, I will mark this PR as ready for review.

[tylerfanelli]

With these changes, I'm encountering the following unexpected error immediately after the VM starts:

Starting TEE/microVM.
[2024-12-12T06:43:33Z ERROR vmm::linux::vstate] Unexpected exit reason on vcpu run: MemoryFault { flags: 8, gpa: 4096, size: 4096 }

Will investigate.

[tylerfanelli]

I'd also like to modify this to create one guest_memfd and map all guest memory regions into it (using the kvm_userspace_memory_region2.guest_memfd_offset field) rather than creating a new guest_memfd for each region of guest memory.

[jakecorrenti]

With these changes, I'm encountering the following unexpected error immediately after the VM starts:

Starting TEE/microVM.
[2024-12-12T06:43:33Z ERROR vmm::linux::vstate] Unexpected exit reason on vcpu run: MemoryFault { flags: 8, gpa: 4096, size: 4096 }

Will investigate.

I know in TDX you need to also set memory attributes after creating the guest memfd and setting the user memory region. I wonder if you have to do that here as well?

[tylerfanelli]

With these changes, I'm encountering the following unexpected error immediately after the VM starts:

Starting TEE/microVM.
[2024-12-12T06:43:33Z ERROR vmm::linux::vstate] Unexpected exit reason on vcpu run: MemoryFault { flags: 8, gpa: 4096, size: 4096 }

Will investigate.

I know in TDX you need to also set memory attributes after creating the guest memfd and setting the user memory region. I wonder if you have to do that here as well?

Do you? I wasn't aware of this. Will try it out.

[jakecorrenti]

With these changes, I'm encountering the following unexpected error immediately after the VM starts:

Starting TEE/microVM.
[2024-12-12T06:43:33Z ERROR vmm::linux::vstate] Unexpected exit reason on vcpu run: MemoryFault { flags: 8, gpa: 4096, size: 4096 }

Will investigate.

I know in TDX you need to also set memory attributes after creating the guest memfd and setting the user memory region. I wonder if you have to do that here as well?

Do you? I wasn't aware of this. Will try it out.

let attr = kvm_memory_attributes {
    address: region.start_addr().raw_value(),
    size: region.len() as u64,
    // KVM_MEMORY_ATTRIBUTE_PRIVATE,
    attributes: 1 << 3,
    flags: 0,
};

self.fd
    .set_memory_attributes(attr)
    .map_err(Error::SetMemoryAttributes)?;

Should do the job. Hopefully this saves you time and avoids you having to dig around for it.