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From:   Ross Philipson <ross.philipson@oracle.com>
To:     linux-kernel@vger.kernel.org, x86@kernel.org,
        iommu@lists.linux-foundation.org, linux-integrity@vger.kernel.org,
        linux-doc@vger.kernel.org
Cc:     ross.philipson@oracle.com, dpsmith@apertussolutions.com,
        tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, hpa@zytor.com,
        luto@amacapital.net, trenchboot-devel@googlegroups.com
Subject: [PATCH 11/13] kexec: Secure Launch kexec SEXIT support
Date:   Thu, 24 Sep 2020 10:58:39 -0400
Message-Id: <1600959521-24158-12-git-send-email-ross.philipson@oracle.com>
In-Reply-To: <1600959521-24158-1-git-send-email-ross.philipson@oracle.com>
References: <1600959521-24158-1-git-send-email-ross.philipson@oracle.com>
Precedence: bulk

Prior to running the next kernel via kexec, the Secure Launch code
closes down private SMX resources and does an SEXIT. This allows the
next kernel to start normally without any issues starting the APs etc.

Signed-off-by: Ross Philipson <ross.philipson@oracle.com>
---
 arch/x86/kernel/slaunch.c | 70 +++++++++++++++++++++++++++++++++++++++++++++++
 kernel/kexec_core.c       |  4 +++
 2 files changed, 74 insertions(+)

diff --git a/arch/x86/kernel/slaunch.c b/arch/x86/kernel/slaunch.c
index 7bdb89e..b2221d8 100644
--- a/arch/x86/kernel/slaunch.c
+++ b/arch/x86/kernel/slaunch.c
@@ -784,3 +784,73 @@ static void __exit slaunch_exit(void)
 late_initcall(slaunch_late_init);
 
 __exitcall(slaunch_exit);
+
+static inline void smx_getsec_sexit(void)
+{
+	asm volatile (".byte 0x0f,0x37\n"
+		      : : "a" (SMX_X86_GETSEC_SEXIT));
+}
+
+void slaunch_finalize(int do_sexit)
+{
+	void __iomem *config;
+	u64 one = 1, val;
+
+	if (!(slaunch_get_flags() & (SL_FLAG_ACTIVE|SL_FLAG_ARCH_TXT)))
+		return;
+
+	config = ioremap(TXT_PRIV_CONFIG_REGS_BASE, TXT_NR_CONFIG_PAGES *
+			 PAGE_SIZE);
+	if (!config) {
+		pr_emerg("Error SEXIT failed to ioremap TXT private reqs\n");
+		return;
+	}
+
+	/* Clear secrets bit for SEXIT */
+	memcpy_toio(config + TXT_CR_CMD_NO_SECRETS, &one, sizeof(u64));
+	memcpy_fromio(&val, config + TXT_CR_E2STS, sizeof(u64));
+
+	/* Unlock memory configurations */
+	memcpy_toio(config + TXT_CR_CMD_UNLOCK_MEM_CONFIG, &one, sizeof(u64));
+	memcpy_fromio(&val, config + TXT_CR_E2STS, sizeof(u64));
+
+	/* Close the TXT private register space */
+	memcpy_fromio(&val, config + TXT_CR_E2STS, sizeof(u64));
+	memcpy_toio(config + TXT_CR_CMD_CLOSE_PRIVATE, &one, sizeof(u64));
+
+	/*
+	 * Calls to iounmap are not being done because of the state of the
+	 * system this late in the kexec process. Local IRQs are disabled and
+	 * iounmap causes a TLB flush which in turn causes a warning. Leaving
+	 * thse mappings is not an issue since the next kernel is going to
+	 * completely re-setup memory management.
+	 */
+
+	/* Map public registers and do a final read fence */
+	config = ioremap(TXT_PUB_CONFIG_REGS_BASE, TXT_NR_CONFIG_PAGES *
+			 PAGE_SIZE);
+	if (!config) {
+		pr_emerg("Error SEXIT failed to ioremap TXT public reqs\n");
+		return;
+	}
+
+	memcpy_fromio(&val, config + TXT_CR_E2STS, sizeof(u64));
+
+	pr_emerg("TXT clear secrets bit and unlock memory complete.");
+
+	if (!do_sexit)
+		return;
+
+	if (smp_processor_id() != 0) {
+		pr_emerg("Error TXT SEXIT must be called on CPU 0\n");
+		return;
+	}
+
+	/* Disable SMX mode */
+	cr4_set_bits(X86_CR4_SMXE);
+
+	/* Do the SEXIT SMX operation */
+	smx_getsec_sexit();
+
+	pr_emerg("TXT SEXIT complete.");
+}
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index c19c0da..6b9ac11 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -37,6 +37,7 @@
 #include <linux/compiler.h>
 #include <linux/hugetlb.h>
 #include <linux/frame.h>
+#include <linux/slaunch.h>
 
 #include <asm/page.h>
 #include <asm/sections.h>
@@ -1179,6 +1180,9 @@ int kernel_kexec(void)
 		cpu_hotplug_enable();
 		pr_notice("Starting new kernel\n");
 		machine_shutdown();
+
+		/* Finalize TXT registers and do SEXIT */
+		slaunch_finalize(1);
 	}
 
 	machine_kexec(kexec_image);
-- 
1.8.3.1