[Xen-devel] [PATCH] setup vwfi correctly on cpu0

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

parse_vwfi runs after init_traps on cpu0, potentially resulting in the
wrong HCR_EL2 for it. Secondary cpus boot after parse_vwfi, so in their
case init_traps will write the correct set of flags to HCR_EL2.

For cpu0, fix the issue by changing HCR_EL2 setting directly in
parse_vwfi.

Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

---
This patch should be apply to 4.8, 4.7, 4.6, not to unstable (it will be
fixed differently there).
---
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 614501f..94d2e8a 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -112,6 +112,16 @@ static void __init parse_vwfi(const char *s)
                vwfi = NATIVE;
        else
                vwfi = TRAP;
+    /*
+     * HCR_EL2 has already been set on cpu0, change the setting here, if
+     * needed. Other cpus haven't booted yet, init_traps will setup
+     * HCR_EL2 correctly.
+     */
+    if (vwfi == NATIVE) {
+        register_t hcr;
+        hcr = READ_SYSREG(HCR_EL2);
+        WRITE_SYSREG(hcr & ~(HCR_TWI|HCR_TWE), HCR_EL2);
+    }
 }
 custom_param("vwfi", parse_vwfi);
 

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