linux-kernel - [tip: x86/seves] x86/sev-es: Add CPUID handling to #VC handler

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Message-ID: <159972974133.20229.5160639798798149324.tip-bot2@tip-bot2>
Date:   Thu, 10 Sep 2020 09:22:21 -0000
From:   "tip-bot2 for Tom Lendacky" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Tom Lendacky <thomas.lendacky@....com>,
        Joerg Roedel <jroedel@...e.de>, Borislav Petkov <bp@...e.de>,
        x86 <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>
Subject: [tip: x86/seves] x86/sev-es: Add CPUID handling to #VC handler

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

Commit-ID:     a7de15d489d956217b47671705ac2218ca50eaae
Gitweb:        https://git.kernel.org/tip/a7de15d489d956217b47671705ac2218ca50eaae
Author:        Tom Lendacky <thomas.lendacky@....com>
AuthorDate:    Mon, 07 Sep 2020 15:15:28 +02:00
Committer:     Borislav Petkov <bp@...e.de>
CommitterDate: Mon, 07 Sep 2020 20:15:51 +02:00

x86/sev-es: Add CPUID handling to #VC handler

Handle #VC exceptions caused by CPUID instructions. These happen in
early boot code when the KASLR code checks for RDTSC.

Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
[ jroedel@...e.de: Adapt to #VC handling framework ]
Co-developed-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Joerg Roedel <jroedel@...e.de>
Signed-off-by: Borislav Petkov <bp@...e.de>
Link: https://lkml.kernel.org/r/20200907131613.12703-28-joro@8bytes.org
---
 arch/x86/boot/compressed/sev-es.c |  4 +++-
 arch/x86/kernel/sev-es-shared.c   | 35 ++++++++++++++++++++++++++++++-
 2 files changed, 39 insertions(+)

diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c
index 61504eb..b1790f4 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -16,6 +16,7 @@
 #include <asm/trapnr.h>
 #include <asm/trap_pf.h>
 #include <asm/msr-index.h>
+#include <asm/fpu/xcr.h>
 #include <asm/ptrace.h>
 #include <asm/svm.h>
 
@@ -183,6 +184,9 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code)
 	case SVM_EXIT_IOIO:
 		result = vc_handle_ioio(boot_ghcb, &ctxt);
 		break;
+	case SVM_EXIT_CPUID:
+		result = vc_handle_cpuid(boot_ghcb, &ctxt);
+		break;
 	default:
 		result = ES_UNSUPPORTED;
 		break;
diff --git a/arch/x86/kernel/sev-es-shared.c b/arch/x86/kernel/sev-es-shared.c
index bae7cf2..a6b4191 100644
--- a/arch/x86/kernel/sev-es-shared.c
+++ b/arch/x86/kernel/sev-es-shared.c
@@ -432,3 +432,38 @@ static enum es_result vc_handle_ioio(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
 
 	return ret;
 }
+
+static enum es_result vc_handle_cpuid(struct ghcb *ghcb,
+				      struct es_em_ctxt *ctxt)
+{
+	struct pt_regs *regs = ctxt->regs;
+	u32 cr4 = native_read_cr4();
+	enum es_result ret;
+
+	ghcb_set_rax(ghcb, regs->ax);
+	ghcb_set_rcx(ghcb, regs->cx);
+
+	if (cr4 & X86_CR4_OSXSAVE)
+		/* Safe to read xcr0 */
+		ghcb_set_xcr0(ghcb, xgetbv(XCR_XFEATURE_ENABLED_MASK));
+	else
+		/* xgetbv will cause #GP - use reset value for xcr0 */
+		ghcb_set_xcr0(ghcb, 1);
+
+	ret = sev_es_ghcb_hv_call(ghcb, ctxt, SVM_EXIT_CPUID, 0, 0);
+	if (ret != ES_OK)
+		return ret;
+
+	if (!(ghcb_rax_is_valid(ghcb) &&
+	      ghcb_rbx_is_valid(ghcb) &&
+	      ghcb_rcx_is_valid(ghcb) &&
+	      ghcb_rdx_is_valid(ghcb)))
+		return ES_VMM_ERROR;
+
+	regs->ax = ghcb->save.rax;
+	regs->bx = ghcb->save.rbx;
+	regs->cx = ghcb->save.rcx;
+	regs->dx = ghcb->save.rdx;
+
+	return ES_OK;
+}