[Patch v3 4/4] x86/hyperv: Add guest support for Enhanced SMT Protection

["Pratik R. Sampat" <prsampat@amd.com>]

Add corresponding hyperv support for Enhanced SMT protection. A fully
enlightened SEV-SNP guest on Hyper-V builds the VMSA itself when
bringing up an AP, so populate both fields there, before the page is
turned into a VMSA and while it is still writable.

Similar to KVM, fully set the sibling mask so that all threads of the
same guest trust each other.

Signed-off-by: Pratik R. Sampat <prsampat@amd.com>
---
v2..v3: No changes

v1..v2: New patch
---
 arch/x86/hyperv/ivm.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c
index 2ce4dfe53472..40dd252f333a 100644
--- a/arch/x86/hyperv/ivm.c
+++ b/arch/x86/hyperv/ivm.c
@@ -347,6 +347,17 @@ int hv_snp_boot_ap(u32 apic_id, unsigned long start_ip, unsigned int cpu)
 	vmsa->vmpl = 0;
 	vmsa->sev_features = sev_status >> 2;
 
+	if (sev_status & MSR_AMD64_SNP_ESMT_PROT) {
+		vmsa->vcpu_id = apic_id;
+		/*
+		 * The mask fully set puts every vCPU in one group, so any two
+		 * of them may be co-resident. A legal ESMTP sibling must
+		 * also match on ASID, so the sibling of a vCPU in guest mode is
+		 * always either another vCPU of this same guest or idle.
+		 */
+		vmsa->vcpu_sibling_mask = U32_MAX;
+	}
+
 	ret = snp_set_vmsa(vmsa, true);
 	if (ret) {
 		pr_err("RMPADJUST(%llx) failed: %llx\n", (u64)vmsa, ret);
-- 
2.43.0