[tip: x86/seves] x86/paravirt: Allow hypervisor-specific VMMCALL handling under SEV-ES

["tip-bot2 for Joerg Roedel" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/seves branch of tip:

Commit-ID:     f6a9f8a45810d2914ea422ff39bfe2e0251c50f2
Gitweb:        https://git.kernel.org/tip/f6a9f8a45810d2914ea422ff39bfe2e0251c50f2
Author:        Joerg Roedel <jroedel@suse.de>
AuthorDate:    Mon, 07 Sep 2020 15:16:03 +02:00
Committer:     Borislav Petkov <bp@suse.de>
CommitterDate: Wed, 09 Sep 2020 11:33:20 +02:00

x86/paravirt: Allow hypervisor-specific VMMCALL handling under SEV-ES

Add two new paravirt callbacks to provide hypervisor-specific processor
state in the GHCB and to copy state from the hypervisor back to the
processor.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-63-joro@8bytes.org
---
 arch/x86/include/asm/x86_init.h | 16 +++++++++++++++-
 arch/x86/kernel/sev-es.c        | 12 ++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/x86_init.h b/arch/x86/include/asm/x86_init.h
index 6807153..0304e29 100644
--- a/arch/x86/include/asm/x86_init.h
+++ b/arch/x86/include/asm/x86_init.h
@@ -4,8 +4,10 @@
 
 #include <asm/bootparam.h>
 
+struct ghcb;
 struct mpc_bus;
 struct mpc_cpu;
+struct pt_regs;
 struct mpc_table;
 struct cpuinfo_x86;
 
@@ -236,10 +238,22 @@ struct x86_legacy_features {
 /**
  * struct x86_hyper_runtime - x86 hypervisor specific runtime callbacks
  *
- * @pin_vcpu:		pin current vcpu to specified physical cpu (run rarely)
+ * @pin_vcpu:			pin current vcpu to specified physical
+ *				cpu (run rarely)
+ * @sev_es_hcall_prepare:	Load additional hypervisor-specific
+ *				state into the GHCB when doing a VMMCALL under
+ *				SEV-ES. Called from the #VC exception handler.
+ * @sev_es_hcall_finish:	Copies state from the GHCB back into the
+ *				processor (or pt_regs). Also runs checks on the
+ *				state returned from the hypervisor after a
+ *				VMMCALL under SEV-ES.  Needs to return 'false'
+ *				if the checks fail.  Called from the #VC
+ *				exception handler.
  */
 struct x86_hyper_runtime {
 	void (*pin_vcpu)(int cpu);
+	void (*sev_es_hcall_prepare)(struct ghcb *ghcb, struct pt_regs *regs);
+	bool (*sev_es_hcall_finish)(struct ghcb *ghcb, struct pt_regs *regs);
 };
 
 /**
diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 79d5190..6d89df9 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -897,6 +897,9 @@ static enum es_result vc_handle_vmmcall(struct ghcb *ghcb,
 	ghcb_set_rax(ghcb, ctxt->regs->ax);
 	ghcb_set_cpl(ghcb, user_mode(ctxt->regs) ? 3 : 0);
 
+	if (x86_platform.hyper.sev_es_hcall_prepare)
+		x86_platform.hyper.sev_es_hcall_prepare(ghcb, ctxt->regs);
+
 	ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_VMMCALL, 0, 0);
 	if (ret != ES_OK)
 		return ret;
@@ -906,6 +909,15 @@ static enum es_result vc_handle_vmmcall(struct ghcb *ghcb,
 
 	ctxt->regs->ax = ghcb->save.rax;
 
+	/*
+	 * Call sev_es_hcall_finish() after regs->ax is already set.
+	 * This allows the hypervisor handler to overwrite it again if
+	 * necessary.
+	 */
+	if (x86_platform.hyper.sev_es_hcall_finish &&
+	    !x86_platform.hyper.sev_es_hcall_finish(ghcb, ctxt->regs))
+		return ES_VMM_ERROR;
+
 	return ES_OK;
 }