[PATCH v7 19/19] hvf: arm: Handle Windows 10 SMC call

[Alexander Graf <agraf@csgraf.de>]

Windows 10 calls an SMCCC call via SMC unconditionally on boot. It lives
in the trusted application call number space, but its purpose is unknown.

In our current SMC implementation, we inject a UDEF for unknown SMC calls,
including this one. However, Windows breaks on boot when we do this. Instead,
let's return an error code.

With this patch applied I can successfully boot the current Windows 10
Insider Preview in HVF.

Signed-off-by: Alexander Graf <agraf@csgraf.de>
---
 target/arm/hvf/hvf.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/target/arm/hvf/hvf.c b/target/arm/hvf/hvf.c
index acf8fd4060..12dd5bbb0c 100644
--- a/target/arm/hvf/hvf.c
+++ b/target/arm/hvf/hvf.c
@@ -928,6 +928,10 @@ int hvf_vcpu_exec(CPUState *cpu)
         cpu_synchronize_state(cpu);
         if (!hvf_handle_psci_call(cpu)) {
             advance_pc = true;
+        } else if (env->xregs[0] == QEMU_SMCCC_TC_WINDOWS10_BOOT) {
+            /* This special SMC is called by Windows 10 on boot. Return error. */
+            env->xregs[0] = -1;
+            advance_pc = true;
         } else {
             trace_hvf_unknown_smc(env->xregs[0]);
             hvf_raise_exception(env, EXCP_UDEF, syn_uncategorized());
-- 
2.30.1 (Apple Git-130)