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Diffstat (limited to 'arch/x86/hyperv/hv_init.c')
-rw-r--r--arch/x86/hyperv/hv_init.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 6c04b52f139b..953e280c07c3 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -14,6 +14,7 @@
#include <asm/apic.h>
#include <asm/desc.h>
#include <asm/sev.h>
+#include <asm/ibt.h>
#include <asm/hypervisor.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
@@ -472,6 +473,26 @@ void __init hyperv_init(void)
}
/*
+ * Some versions of Hyper-V that provide IBT in guest VMs have a bug
+ * in that there's no ENDBR64 instruction at the entry to the
+ * hypercall page. Because hypercalls are invoked via an indirect call
+ * to the hypercall page, all hypercall attempts fail when IBT is
+ * enabled, and Linux panics. For such buggy versions, disable IBT.
+ *
+ * Fixed versions of Hyper-V always provide ENDBR64 on the hypercall
+ * page, so if future Linux kernel versions enable IBT for 32-bit
+ * builds, additional hypercall page hackery will be required here
+ * to provide an ENDBR32.
+ */
+#ifdef CONFIG_X86_KERNEL_IBT
+ if (cpu_feature_enabled(X86_FEATURE_IBT) &&
+ *(u32 *)hv_hypercall_pg != gen_endbr()) {
+ setup_clear_cpu_cap(X86_FEATURE_IBT);
+ pr_warn("Hyper-V: Disabling IBT because of Hyper-V bug\n");
+ }
+#endif
+
+ /*
* hyperv_init() is called before LAPIC is initialized: see
* apic_intr_mode_init() -> x86_platform.apic_post_init() and
* apic_bsp_setup() -> setup_local_APIC(). The direct-mode STIMER