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hypervisor: Add support for handling #HV Doorbell Page

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As part of this handling there are 4 different operations:

1. Getting the hypervisor preffered doorbell page GPA.
2. Informing hypervisor about the doorbell page chosen by the guest
3. Querying the GPA of the doorbell page
4. Clearing the GPA of the doorbell page from hypervisor

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>
Signed-off-by: Muminul Islam <muislam@microsoft.com>
This commit is contained in:
Jinank Jain 2023-10-19 03:05:02 +00:00 committed by Bo Chen
parent d6db3a9d32
commit cb5ea05945
3 changed files with 136 additions and 0 deletions
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10
hypervisor/src/cpu.rs
View File

@ -257,6 +257,16 @@ pub enum HypervisorCpuError {
///
#[error("Failed to set TSC frequency: {0}")]
SetTscKhz(#[source] anyhow::Error),
///
/// Error reading value at given GPA
///
#[error("Failed to read from GPA: {0}")]
GpaRead(#[source] anyhow::Error),
///
/// Error writing value at given GPA
///
#[error("Failed to write to GPA: {0}")]
GpaWrite(#[source] anyhow::Error),
}
#[derive(Debug)]

121
hypervisor/src/mshv/mod.rs
View File

@ -716,6 +716,127 @@ impl cpu::Vcpu for MshvVcpu {
set_registers_64!(self.fd, arr_reg_name_value)
.map_err(|e| cpu::HypervisorCpuError::SetRegister(e.into()))?;
}
GHCB_INFO_NORMAL => {
let exit_code =
info.__bindgen_anon_2.__bindgen_anon_1.sw_exit_code as u32;
// SAFETY: Accessing a union element from bindgen generated bindings.
let pfn = unsafe { ghcb_msr.__bindgen_anon_2.gpa_page_number() };
let ghcb_gpa = pfn << GHCB_INFO_BIT_WIDTH;
match exit_code {
SVM_EXITCODE_HV_DOORBELL_PAGE => {
let exit_info1 =
info.__bindgen_anon_2.__bindgen_anon_1.sw_exit_info1 as u32;
match exit_info1 {
SVM_NAE_HV_DOORBELL_PAGE_GET_PREFERRED => {
// Hypervisor does not have any preference for doorbell GPA.
let preferred_doorbell_gpa: u64 = 0xFFFFFFFFFFFFFFFF;
let mut swei2_rw_gpa_arg =
mshv_bindings::mshv_read_write_gpa {
base_gpa: ghcb_gpa + GHCB_SW_EXITINFO2_OFFSET,
byte_count: std::mem::size_of::<u64>() as u32,
..Default::default()
};
swei2_rw_gpa_arg.data.copy_from_slice(
&preferred_doorbell_gpa.to_le_bytes(),
);
self.fd.gpa_write(&mut swei2_rw_gpa_arg).map_err(
|e| cpu::HypervisorCpuError::GpaWrite(e.into()),
)?;
}
SVM_NAE_HV_DOORBELL_PAGE_SET => {
let exit_info2 = info
.__bindgen_anon_2
.__bindgen_anon_1
.sw_exit_info2;
let mut ghcb_doorbell_gpa =
hv_x64_register_sev_hv_doorbell::default();
// SAFETY: Accessing a union element from bindgen generated bindings.
unsafe {
ghcb_doorbell_gpa.__bindgen_anon_1.set_enabled(1);
ghcb_doorbell_gpa
.__bindgen_anon_1
.set_page_number(exit_info2 >> PAGE_SHIFT);
}
// SAFETY: Accessing a union element from bindgen generated bindings.
let reg_names = unsafe {
[(
hv_register_name_HV_X64_REGISTER_SEV_DOORBELL_GPA,
ghcb_doorbell_gpa.as_uint64,
)]
};
set_registers_64!(self.fd, reg_names).map_err(|e| {
cpu::HypervisorCpuError::SetRegister(e.into())
})?;
let mut swei2_rw_gpa_arg =
mshv_bindings::mshv_read_write_gpa {
base_gpa: ghcb_gpa + GHCB_SW_EXITINFO2_OFFSET,
byte_count: std::mem::size_of::<u64>() as u32,
..Default::default()
};
swei2_rw_gpa_arg.data[0..8]
.copy_from_slice(&exit_info2.to_le_bytes());
self.fd.gpa_write(&mut swei2_rw_gpa_arg).map_err(
|e| cpu::HypervisorCpuError::GpaWrite(e.into()),
)?;
// Clear the SW_EXIT_INFO1 register to indicate no error
let mut swei1_rw_gpa_arg =
mshv_bindings::mshv_read_write_gpa {
base_gpa: ghcb_gpa + GHCB_SW_EXITINFO1_OFFSET,
byte_count: std::mem::size_of::<u64>() as u32,
..Default::default()
};
self.fd.gpa_write(&mut swei1_rw_gpa_arg).map_err(
|e| cpu::HypervisorCpuError::GpaWrite(e.into()),
)?;
}
SVM_NAE_HV_DOORBELL_PAGE_QUERY => {
let mut reg_assocs = [ hv_register_assoc {
name: hv_register_name_HV_X64_REGISTER_SEV_DOORBELL_GPA,
..Default::default()
} ];
self.fd.get_reg(&mut reg_assocs).unwrap();
// SAFETY: Accessing a union element from bindgen generated bindings.
let doorbell_gpa = unsafe { reg_assocs[0].value.reg64 };
let mut swei2_rw_gpa_arg =
mshv_bindings::mshv_read_write_gpa {
base_gpa: ghcb_gpa + GHCB_SW_EXITINFO2_OFFSET,
byte_count: std::mem::size_of::<u64>() as u32,
..Default::default()
};
swei2_rw_gpa_arg
.data
.copy_from_slice(&doorbell_gpa.to_le_bytes());
self.fd.gpa_write(&mut swei2_rw_gpa_arg).map_err(
|e| cpu::HypervisorCpuError::GpaWrite(e.into()),
)?;
}
SVM_NAE_HV_DOORBELL_PAGE_CLEAR => {
let mut swei2_rw_gpa_arg =
mshv_bindings::mshv_read_write_gpa {
base_gpa: ghcb_gpa + GHCB_SW_EXITINFO2_OFFSET,
byte_count: std::mem::size_of::<u64>() as u32,
..Default::default()
};
self.fd.gpa_write(&mut swei2_rw_gpa_arg).map_err(
|e| cpu::HypervisorCpuError::GpaWrite(e.into()),
)?;
}
_ => {
panic!(
"SVM_EXITCODE_HV_DOORBELL_PAGE: Unhandled exit code: {:0x}",
exit_info1
);
}
}
}
_ => panic!(
"GHCB_INFO_NORMAL: Unhandled exit code: {:0x}",
exit_code
),
}
}
_ => panic!("Unsupported VMGEXIT operation: {:0x}", ghcb_op),
}

5
hypervisor/src/mshv/snp_constants.rs
View File

@ -16,3 +16,8 @@ pub const ECDSA_SIG_X_COMPONENT_END: usize =
pub const ECDSA_SIG_Y_COMPONENT_START: usize = ECDSA_SIG_X_COMPONENT_END;
pub const ECDSA_SIG_Y_COMPONENT_END: usize =
ECDSA_SIG_X_COMPONENT_END + ECDSA_SIG_Y_COMPONENT_SIZE_IN_BYTES;
// These constants are derived from GHCB spec Sect. 2.6 Table 3 GHCB Layout
// Link: https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/56421.pdf
pub const GHCB_SW_EXITINFO1_OFFSET: u64 = 0x398;
pub const GHCB_SW_EXITINFO2_OFFSET: u64 = 0x3A0;