From a50c5bebc99c525e7fbc059988c6a5ab8680cb76 Mon Sep 17 00:00:00 2001
From: Tom Lendacky <thomas.lendacky@amd.com>
Date: Mon, 17 May 2021 12:42:33 -0500
Subject: [PATCH] x86/sev-es: Invalidate the GHCB after completing VMGEXIT
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 it is always presented
as 0 when VMGEXIT has been issued by anything else besides the kernel.
Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/5a8130462e4f0057ee1184509cd056eedd78742b.1621273353.git.thomas.lendacky@amd.com
---
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 6ec8b3bfd76eb..9f90f460a28cc 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 45e212675811c..4fa111becc93b 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;
}
}
--
GitLab