[PATCH v2 1/2] x86/sev-es: Move sev_es_put_ghcb() in prep for follow on patch

[PATCH v2 1/2] x86/sev-es: Move sev_es_put_ghcb() in prep for follow on patch

[Tom Lendacky]

Move the location of sev_es_put_ghcb() in preparation for an update to it
in a follow-on patch. This will better highlight the changes being made
to the function.

No functional change.

Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
Cc: stable@vger.kernel.org
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/kernel/sev.c | 36 ++++++++++++++++++------------------
 1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
index 9578c82832aa..45e212675811 100644
--- a/arch/x86/kernel/sev.c
+++ b/arch/x86/kernel/sev.c
@@ -221,24 +221,6 @@ static __always_inline struct ghcb *sev_es_get_ghcb(struct ghcb_state *state)
 	return ghcb;
 }
 
-static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
-{
-	struct sev_es_runtime_data *data;
-	struct ghcb *ghcb;
-
-	data = this_cpu_read(runtime_data);
-	ghcb = &data->ghcb_page;
-
-	if (state->ghcb) {
-		/* Restore GHCB from Backup */
-		*ghcb = *state->ghcb;
-		data->backup_ghcb_active = false;
-		state->ghcb = NULL;
-	} else {
-		data->ghcb_active = false;
-	}
-}
-
 /* Needed in vc_early_forward_exception */
 void do_early_exception(struct pt_regs *regs, int trapnr);
 
@@ -461,6 +443,24 @@ static enum es_result vc_slow_virt_to_phys(struct ghcb *ghcb, struct es_em_ctxt
 /* Include code shared with pre-decompression boot stage */
 #include "sev-shared.c"
 
+static __always_inline void sev_es_put_ghcb(struct ghcb_state *state)
+{
+	struct sev_es_runtime_data *data;
+	struct ghcb *ghcb;
+
+	data = this_cpu_read(runtime_data);
+	ghcb = &data->ghcb_page;
+
+	if (state->ghcb) {
+		/* Restore GHCB from Backup */
+		*ghcb = *state->ghcb;
+		data->backup_ghcb_active = false;
+		state->ghcb = NULL;
+	} else {
+		data->ghcb_active = false;
+	}
+}
+
 void noinstr __sev_es_nmi_complete(void)
 {
 	struct ghcb_state state;
-- 
2.31.0

[PATCH v2 2/2] x86/sev-es: Invalidate the GHCB after completing VMGEXIT

[Tom Lendacky]

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@vger.kernel.org
Signed-off-by: Tom Lendacky <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 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

Re: [PATCH v2 1/2] x86/sev-es: Move sev_es_put_ghcb() in prep for follow on patch

[Joerg Roedel]

On Mon, May 17, 2021 at 12:42:32PM -0500, Tom Lendacky wrote:
> Move the location of sev_es_put_ghcb() in preparation for an update to it
> in a follow-on patch. This will better highlight the changes being made
> to the function.
> 
> No functional change.
> 
> Fixes: 0786138c78e79 ("x86/sev-es: Add a Runtime #VC Exception Handler")
> Cc: stable@vger.kernel.org
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

Reviewed-by: Joerg Roedel <jroedel@suse.de>

Re: [PATCH v2 2/2] x86/sev-es: Invalidate the GHCB after completing VMGEXIT

[Joerg Roedel]

On Mon, May 17, 2021 at 12:42:33PM -0500, Tom Lendacky wrote:
> 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@vger.kernel.org
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>

Reviewed-by: Joerg Roedel <jroedel@suse.de>