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[50/62] x86/sev-es: Handle VMMCALL Events

Message ID 20200211135256.24617-51-joro@8bytes.org (mailing list archive)
State New, archived
Headers show
Series Linux as SEV-ES Guest Support | expand

Commit Message

Joerg Roedel Feb. 11, 2020, 1:52 p.m. UTC 
From: Tom Lendacky <thomas.lendacky@amd.com>

Implement a handler for #VC exceptions caused by VMMCALL instructions.
This patch is only a starting point, VMMCALL emulation under SEV-ES
needs further hypervisor-specific changes to provide additional state.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
[ jroedel@suse.de: Adapt to #VC handling infrastructure ]
Co-developed-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 arch/x86/kernel/sev-es.c | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

Comments

Andy Lutomirski Feb. 12, 2020, 12:14 a.m. UTC | #1 
> On Feb 11, 2020, at 5:53 AM, Joerg Roedel <joro@8bytes.org> wrote:
> 
> From: Tom Lendacky <thomas.lendacky@amd.com>
> 
> Implement a handler for #VC exceptions caused by VMMCALL instructions.
> This patch is only a starting point, VMMCALL emulation under SEV-ES
> needs further hypervisor-specific changes to provide additional state.
> 

How about we just don’t do VMMCALL if we’re a SEV-ES guest?  Otherwise we add thousands of cycles of extra latency for no good reason.
Joerg Roedel Feb. 12, 2020, 1:22 p.m. UTC | #2 
On Tue, Feb 11, 2020 at 04:14:53PM -0800, Andy Lutomirski wrote:
> 
> How about we just don’t do VMMCALL if we’re a SEV-ES guest?  Otherwise
> we add thousands of cycles of extra latency for no good reason.

True, but I left that as a future optimization for now, given the size
the patch-set already has. The idea is to add an abstraction around
VMMCALL for the support code of the various hypervisors and just do a
VMGEXIT in that wrapper when in an SEV-ES guest. But again, that is a
separate patch-set.

Regards,

	Joerg
diff mbox series

Patch

diff --git a/arch/x86/kernel/sev-es.c b/arch/x86/kernel/sev-es.c
index 8f1e84da6fa6..6bd2cae7eb9c 100644
--- a/arch/x86/kernel/sev-es.c
+++ b/arch/x86/kernel/sev-es.c
@@ -341,6 +341,26 @@  static enum es_result handle_mwait(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 	return ghcb_hv_call(ghcb, ctxt, SVM_EXIT_MWAIT, 0, 0);
 }
 
+static enum es_result handle_vmmcall(struct ghcb *ghcb,
+				     struct es_em_ctxt *ctxt)
+{
+	enum es_result ret;
+
+	ghcb_set_rax(ghcb, ctxt->regs->ax);
+	ghcb_set_cpl(ghcb, user_mode(ctxt->regs) ? 3 : 0);
+
+	ret = ghcb_hv_call(ghcb, ctxt, SVM_EXIT_VMMCALL, 0, 0);
+	if (ret != ES_OK)
+		return ret;
+
+	if (!ghcb_is_valid_rax(ghcb))
+		return ES_VMM_ERROR;
+
+	ctxt->regs->ax = ghcb->save.rax;
+
+	return ES_OK;
+}
+
 static enum es_result handle_vc_exception(struct es_em_ctxt *ctxt,
 					  struct ghcb *ghcb,
 					  unsigned long exit_code,
@@ -374,6 +394,9 @@  static enum es_result handle_vc_exception(struct es_em_ctxt *ctxt,
 	case SVM_EXIT_MSR:
 		result = handle_msr(ghcb, ctxt);
 		break;
+	case SVM_EXIT_VMMCALL:
+		result = handle_vmmcall(ghcb, ctxt);
+		break;
 	case SVM_EXIT_WBINVD:
 		result = handle_wbinvd(ghcb, ctxt);
 		break;