linux-kernel - [RFC 04/16] x86/kvm: Use bounce buffers for KVM memory protection

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Date:   Fri, 22 May 2020 15:52:02 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     Dave Hansen <dave.hansen@...ux.intel.com>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Kees Cook <keescook@...omium.org>,
        Will Drewry <wad@...omium.org>,
        "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [RFC 04/16] x86/kvm: Use bounce buffers for KVM memory protection

Mirror SEV, use SWIOTLB always if KVM memory protection is enabled.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/Kconfig                 |  1 +
 arch/x86/kernel/kvm.c            |  2 ++
 arch/x86/kernel/pci-swiotlb.c    |  3 ++-
 arch/x86/mm/mem_encrypt.c        | 20 --------------------
 arch/x86/mm/mem_encrypt_common.c | 23 +++++++++++++++++++++++
 5 files changed, 28 insertions(+), 21 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 86c012582f51..58dd44a1b92f 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -800,6 +800,7 @@ config KVM_GUEST
 	select PARAVIRT_CLOCK
 	select ARCH_CPUIDLE_HALTPOLL
 	select X86_MEM_ENCRYPT_COMMON
+	select SWIOTLB
 	default y
 	---help---
 	  This option enables various optimizations for running under the KVM
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index bda761ca0d26..f50d65df4412 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -24,6 +24,7 @@
 #include <linux/debugfs.h>
 #include <linux/nmi.h>
 #include <linux/swait.h>
+#include <linux/swiotlb.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>
@@ -742,6 +743,7 @@ static void __init kvm_init_platform(void)
 		}
 
 		mem_protected = true;
+		swiotlb_force = SWIOTLB_FORCE;
 	}
 }
 
diff --git a/arch/x86/kernel/pci-swiotlb.c b/arch/x86/kernel/pci-swiotlb.c
index c2cfa5e7c152..814060a6ceb0 100644
--- a/arch/x86/kernel/pci-swiotlb.c
+++ b/arch/x86/kernel/pci-swiotlb.c
@@ -13,6 +13,7 @@
 #include <asm/dma.h>
 #include <asm/xen/swiotlb-xen.h>
 #include <asm/iommu_table.h>
+#include <asm/kvm_para.h>
 
 int swiotlb __read_mostly;
 
@@ -49,7 +50,7 @@ int __init pci_swiotlb_detect_4gb(void)
 	 * buffers are allocated and used for devices that do not support
 	 * the addressing range required for the encryption mask.
 	 */
-	if (sme_active())
+	if (sme_active() || kvm_mem_protected())
 		swiotlb = 1;
 
 	return swiotlb;
diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
index 112304a706f3..35c748ee3fcb 100644
--- a/arch/x86/mm/mem_encrypt.c
+++ b/arch/x86/mm/mem_encrypt.c
@@ -370,23 +370,3 @@ void __init mem_encrypt_free_decrypted_mem(void)
 
 	free_init_pages("unused decrypted", vaddr, vaddr_end);
 }
-
-void __init mem_encrypt_init(void)
-{
-	if (!sme_me_mask)
-		return;
-
-	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
-	swiotlb_update_mem_attributes();
-
-	/*
-	 * With SEV, we need to unroll the rep string I/O instructions.
-	 */
-	if (sev_active())
-		static_branch_enable(&sev_enable_key);
-
-	pr_info("AMD %s active\n",
-		sev_active() ? "Secure Encrypted Virtualization (SEV)"
-			     : "Secure Memory Encryption (SME)");
-}
-
diff --git a/arch/x86/mm/mem_encrypt_common.c b/arch/x86/mm/mem_encrypt_common.c
index a878e7f246d5..7900f3788010 100644
--- a/arch/x86/mm/mem_encrypt_common.c
+++ b/arch/x86/mm/mem_encrypt_common.c
@@ -37,3 +37,26 @@ bool force_dma_unencrypted(struct device *dev)
 
 	return false;
 }
+
+void __init mem_encrypt_init(void)
+{
+	if (!sme_me_mask && !kvm_mem_protected())
+		return;
+
+	/* Call into SWIOTLB to update the SWIOTLB DMA buffers */
+	swiotlb_update_mem_attributes();
+
+	/*
+	 * With SEV, we need to unroll the rep string I/O instructions.
+	 */
+	if (sev_active())
+		static_branch_enable(&sev_enable_key);
+
+	if (sme_me_mask) {
+		pr_info("AMD %s active\n",
+			sev_active() ? "Secure Encrypted Virtualization (SEV)"
+			: "Secure Memory Encryption (SME)");
+	} else {
+		pr_info("KVM memory protection enabled\n");
+	}
+}
-- 
2.26.2