add ax88772_rst

hc

2024-05-10 9999e48639b3cecb08ffb37358bcba3b48161b29

 kernel/arch/x86/mm/mem_encrypt_identity.c
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@@ -1,13 +1,10 @@
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+// SPDX-License-Identifier: GPL-2.0-only
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 /*
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  * AMD Memory Encryption Support
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  *
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  * Copyright (C) 2016 Advanced Micro Devices, Inc.
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  *
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  * Author: Tom Lendacky <thomas.lendacky@amd.com>
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- *
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- * This program is free software; you can redistribute it and/or modify
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- * it under the terms of the GNU General Public License version 2 as
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- * published by the Free Software Foundation.
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  */
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 #define DISABLE_BRANCH_PROFILING
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@@ -27,6 +24,7 @@
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  * be extended when new paravirt and debugging variants are added.)
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  */
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 #undef CONFIG_PARAVIRT
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+#undef CONFIG_PARAVIRT_XXL
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 #undef CONFIG_PARAVIRT_SPINLOCKS
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 /*
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@@ -80,6 +78,19 @@
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 	unsigned long vaddr;
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 	unsigned long vaddr_end;
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 };
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+
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+/*
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+ * This work area lives in the .init.scratch section, which lives outside of
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+ * the kernel proper. It is sized to hold the intermediate copy buffer and
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+ * more than enough pagetable pages.
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+ *
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+ * By using this section, the kernel can be encrypted in place and it
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+ * avoids any possibility of boot parameters or initramfs images being
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+ * placed such that the in-place encryption logic overwrites them.  This
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+ * section is 2MB aligned to allow for simple pagetable setup using only
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+ * PMD entries (see vmlinux.lds.S).
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+ */
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+static char sme_workarea[2 * PMD_PAGE_SIZE] __section(".init.scratch");
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 static char sme_cmdline_arg[] __initdata = "mem_encrypt";
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 static char sme_cmdline_on[]  __initdata = "on";
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@@ -322,8 +333,13 @@
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 	}
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 #endif
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-	/* Set the encryption workarea to be immediately after the kernel */
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-	workarea_start = kernel_end;
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+	/*
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+	 * We're running identity mapped, so we must obtain the address to the
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+	 * SME encryption workarea using rip-relative addressing.
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+	 */
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+	asm ("lea sme_workarea(%%rip), %0"
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+	     : "=r" (workarea_start)
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+	     : "p" (sme_workarea));
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 	/*
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 	 * Calculate required number of workarea bytes needed:
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@@ -496,14 +512,6 @@
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 #define AMD_SME_BIT	BIT(0)
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 #define AMD_SEV_BIT	BIT(1)
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-	/*
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-	 * Set the feature mask (SME or SEV) based on whether we are
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-	 * running under a hypervisor.
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-	 */
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-	eax = 1;
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-	ecx = 0;
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-	native_cpuid(&eax, &ebx, &ecx, &edx);
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-	feature_mask = (ecx & BIT(31)) ? AMD_SEV_BIT : AMD_SME_BIT;
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 	/*
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 	 * Check for the SME/SEV feature:
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@@ -516,23 +524,38 @@
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 	eax = 0x8000001f;
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 	ecx = 0;
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 	native_cpuid(&eax, &ebx, &ecx, &edx);
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-	if (!(eax & feature_mask))
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+	/* Check whether SEV or SME is supported */
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+	if (!(eax & (AMD_SEV_BIT | AMD_SME_BIT)))
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 		return;
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 	me_mask = 1UL << (ebx & 0x3f);
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+	/* Check the SEV MSR whether SEV or SME is enabled */
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+	sev_status   = __rdmsr(MSR_AMD64_SEV);
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+	feature_mask = (sev_status & MSR_AMD64_SEV_ENABLED) ? AMD_SEV_BIT : AMD_SME_BIT;
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+
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 	/* Check if memory encryption is enabled */
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 	if (feature_mask == AMD_SME_BIT) {
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+		/*
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+		 * No SME if Hypervisor bit is set. This check is here to
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+		 * prevent a guest from trying to enable SME. For running as a
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+		 * KVM guest the MSR_K8_SYSCFG will be sufficient, but there
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+		 * might be other hypervisors which emulate that MSR as non-zero
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+		 * or even pass it through to the guest.
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+		 * A malicious hypervisor can still trick a guest into this
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+		 * path, but there is no way to protect against that.
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+		 */
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+		eax = 1;
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+		ecx = 0;
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+		native_cpuid(&eax, &ebx, &ecx, &edx);
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+		if (ecx & BIT(31))
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+			return;
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+
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 		/* For SME, check the SYSCFG MSR */
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 		msr = __rdmsr(MSR_K8_SYSCFG);
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 		if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT))
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 			return;
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 	} else {
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-		/* For SEV, check the SEV MSR */
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-		msr = __rdmsr(MSR_AMD64_SEV);
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-		if (!(msr & MSR_AMD64_SEV_ENABLED))
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-			return;
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-
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 		/* SEV state cannot be controlled by a command line option */
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 		sme_me_mask = me_mask;
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 		sev_enabled = true;
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@@ -563,7 +586,8 @@
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 	cmdline_ptr = (const char *)((u64)bp->hdr.cmd_line_ptr |
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 				     ((u64)bp->ext_cmd_line_ptr << 32));
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-	cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer));
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+	if (cmdline_find_option(cmdline_ptr, cmdline_arg, buffer, sizeof(buffer)) < 0)
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+		return;
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 	if (!strncmp(buffer, cmdline_on, sizeof(buffer)))
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 		sme_me_mask = me_mask;