Since the VMGEXIT instruction can be issued from userspace, invalidate
the GHCB after performing VMGEXIT processing in the kernel.
Invalidation is only required after userspace is available, so call
vc_ghcb_invalidate() from sev_es_put_ghcb(). Update vc_ghcb_invalidate()
to additionally clear the GHCB exit code, so that a value of 0 is always
present outside VMGEXIT processing in the kernel.
Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Tom Lendacky <thomas.lendacky@xxxxxxx>
---
arch/x86/kernel/sev-shared.c | 1 +
arch/x86/kernel/sev.c | 5 +++++
2 files changed, 6 insertions(+)
diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c
index 6ec8b3bfd76e..9f90f460a28c 100644
--- a/arch/x86/kernel/sev-shared.c
+++ b/arch/x86/kernel/sev-shared.c
@@ -63,6 +63,7 @@ static bool sev_es_negotiate_protocol(void)
static __always_inline void vc_ghcb_invalidate(struct ghcb *ghcb)
{
+ ghcb->save.sw_exit_code = 0;
memset(ghcb->save.valid_bitmap, 0, sizeof(ghcb->save.valid_bitmap));
}
diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 45e212675811..4fa111becc93 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -457,6 +457,11 @@ static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
data->backup_ghcb_active = false;
state->ghcb = NULL;
} else {
+ /*
+ * Invalidate the GHCB so a VMGEXIT instruction issued
+ * from userspace won't appear to be valid.
+ */
+ vc_ghcb_invalidate(ghcb);
data->ghcb_active = false;
}
}
--
2.31.0
