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hypervisor: mshv: Disable previous GHCB page before setting new one

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CVM guests can configure GHCB page multiple times during it's
lifetime depending on it's requirement. For example a Linux CVM guest
configures a different GHCB page during compressed kernel boot and sets
up a new one after decompressing the kernel. As a cleanup step, VMM
should unset the previous GHCB page before registering a new one for
a particular vcpu thread.

Signed-off-by: Jinank Jain <jinankjain@microsoft.com>
This commit is contained in:
Jinank Jain 2024-08-12 18:31:59 +05:30 committed by Bo Chen
parent 02f146fef8
commit 3fe7d6d904
1 changed files with 41 additions and 0 deletions
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41
hypervisor/src/mshv/mod.rs
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@ -799,6 +799,10 @@ impl cpu::Vcpu for MshvVcpu {
}
GHCB_INFO_REGISTER_REQUEST => {
let mut ghcb_gpa = hv_x64_register_sev_ghcb::default();
// Disable the previously used GHCB page.
self.disable_prev_ghcb_page()?;
// SAFETY: Accessing a union element from bindgen generated bindings.
unsafe {
ghcb_gpa.__bindgen_anon_1.set_enabled(1);
@ -826,6 +830,7 @@ impl cpu::Vcpu for MshvVcpu {
resp_ghcb_msr.__bindgen_anon_2.set_gpa_page_number(
ghcb_msr.__bindgen_anon_2.gpa_page_number(),
);
debug!("GHCB GPA is {:x}", ghcb_gpa.as_uint64);
}
// SAFETY: Accessing a union element from bindgen generated bindings.
let reg_name_value = unsafe {
@ -1456,6 +1461,42 @@ impl cpu::Vcpu for MshvVcpu {
}
impl MshvVcpu {
///
/// Deactivate previously used GHCB page.
///
#[cfg(feature = "sev_snp")]
fn disable_prev_ghcb_page(&self) -> cpu::Result<()> {
let mut reg_assocs = [hv_register_assoc {
name: hv_register_name_HV_X64_REGISTER_SEV_GHCB_GPA,
..Default::default()
}];
self.fd.get_reg(&mut reg_assocs).unwrap();
// SAFETY: Accessing a union element from bindgen generated bindings.
let prev_ghcb_gpa = unsafe { reg_assocs[0].value.reg64 };
debug!("Prev GHCB GPA is {:x}", prev_ghcb_gpa);
let mut ghcb_gpa = hv_x64_register_sev_ghcb::default();
// SAFETY: Accessing a union element from bindgen generated bindings.
unsafe {
ghcb_gpa.__bindgen_anon_1.set_enabled(0);
ghcb_gpa.__bindgen_anon_1.set_page_number(prev_ghcb_gpa);
}
// SAFETY: Accessing a union element from bindgen generated bindings.
let reg_name_value = unsafe {
[(
hv_register_name_HV_X64_REGISTER_SEV_GHCB_GPA,
ghcb_gpa.as_uint64,
)]
};
set_registers_64!(self.fd, reg_name_value)
.map_err(|e| cpu::HypervisorCpuError::SetRegister(e.into()))?;
Ok(())
}
#[cfg(target_arch = "x86_64")]
///
/// X86 specific call that returns the vcpu's current "xcrs".