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hypervisor: Add support for handling VMGEXIT for SEV-SNP guest

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A VMGEXIT exit occurs for any of the listed NAE events in the GHCB
specification [1] (e.g. CPUID, RDMSR/WRMSR, MMIO, port IO, etc.). Some
of these events are handled by hypervisor while other are handled by
VMM. Currently, we are adding support for one such request i.e.,
report supported SEV-SNP features by hypervisor.

[1] GHCB protocol specification:
https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>
Signed-off-by: Muminul Islam <muislam@microsoft.com>
This commit is contained in:
Jinank Jain 2023-10-18 11:22:17 +00:00 committed by Bo Chen
parent 7cba80484b
commit 437e6088e6
1 changed files with 38 additions and 0 deletions
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38
hypervisor/src/mshv/mod.rs
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@ -619,6 +619,44 @@ impl cpu::Vcpu for MshvVcpu {
info.interrupt_vector.try_into().unwrap(),
))
}
#[cfg(feature = "sev_snp")]
hv_message_type_HVMSG_X64_SEV_VMGEXIT_INTERCEPT => {
let info = x.to_vmg_intercept_info().unwrap();
let ghcb_data = info.ghcb_msr >> GHCB_INFO_BIT_WIDTH;
let ghcb_msr = svm_ghcb_msr {
as_uint64: info.ghcb_msr,
};
// SAFETY: Accessing a union element from bindgen generated bindings.
let ghcb_op = unsafe { ghcb_msr.__bindgen_anon_2.ghcb_info() as u32 };
// Sanity check on the header fields before handling other operations.
assert!(info.header.intercept_access_type == HV_INTERCEPT_ACCESS_EXECUTE as u8);
match ghcb_op {
GHCB_INFO_HYP_FEATURE_REQUEST => {
// Pre-condition: GHCB data must be zero
assert!(ghcb_data == 0);
let mut ghcb_response = GHCB_INFO_HYP_FEATURE_RESPONSE as u64;
// Indicate support for basic SEV-SNP features
ghcb_response |=
(GHCB_HYP_FEATURE_SEV_SNP << GHCB_INFO_BIT_WIDTH) as u64;
// Indicate support for SEV-SNP AP creation
ghcb_response |= (GHCB_HYP_FEATURE_SEV_SNP_AP_CREATION
<< GHCB_INFO_BIT_WIDTH)
as u64;
debug!(
"GHCB_INFO_HYP_FEATURE_REQUEST: Supported features: {:0x}",
ghcb_response
);
let arr_reg_name_value =
[(hv_register_name_HV_X64_REGISTER_GHCB, ghcb_response)];
set_registers_64!(self.fd, arr_reg_name_value)
.map_err(|e| cpu::HypervisorCpuError::SetRegister(e.into()))?;
}
_ => panic!("Unsupported VMGEXIT operation: {:0x}", ghcb_op),
}
Ok(cpu::VmExit::Ignore)
}
exit => Err(cpu::HypervisorCpuError::RunVcpu(anyhow!(
"Unhandled VCPU exit {:?}",
exit