On Fri, Mar 20, 2020 at 02:23:58PM -0700, David Rientjes wrote:

On Thu, 19 Mar 2020, Joerg Roedel wrote:

quoted

+#if defined(CONFIG_AMD_MEM_ENCRYPT)
+static void kvm_sev_es_hcall_prepare(struct ghcb *ghcb, struct pt_regs *regs)
+{
+	/* RAX and CPL are already in the GHCB */
+	ghcb_set_rbx(ghcb, regs->bx);
+	ghcb_set_rcx(ghcb, regs->cx);
+	ghcb_set_rdx(ghcb, regs->dx);
+	ghcb_set_rsi(ghcb, regs->si);

Is it possible to check the hypercall from RAX and only copy the needed 
regs or is there a requirement that they must all be copied 
unconditionally?

No, there is no such requirement. This could be optimized with hypercall
specific knowledge as it is in the KVM code anyway.

Regards,

	Joerg