linux-kernel - [RFC 03/16] x86/kvm: Make DMA pages shared

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Date:   Fri, 22 May 2020 15:52:01 +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 03/16] x86/kvm: Make DMA pages shared

Make force_dma_unencrypted() return true for KVM to get DMA pages mapped
as shared.

__set_memory_enc_dec() now informs the host via hypercall if the state
of the page has changed from shared to private or back.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
 arch/x86/Kconfig                 | 1 +
 arch/x86/mm/mem_encrypt_common.c | 5 +++--
 arch/x86/mm/pat/set_memory.c     | 7 +++++++
 include/uapi/linux/kvm_para.h    | 2 ++
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index bc72bfd89bcf..86c012582f51 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -799,6 +799,7 @@ config KVM_GUEST
 	depends on PARAVIRT
 	select PARAVIRT_CLOCK
 	select ARCH_CPUIDLE_HALTPOLL
+	select X86_MEM_ENCRYPT_COMMON
 	default y
 	---help---
 	  This option enables various optimizations for running under the KVM
diff --git a/arch/x86/mm/mem_encrypt_common.c b/arch/x86/mm/mem_encrypt_common.c
index 964e04152417..a878e7f246d5 100644
--- a/arch/x86/mm/mem_encrypt_common.c
+++ b/arch/x86/mm/mem_encrypt_common.c
@@ -10,14 +10,15 @@
 #include <linux/mm.h>
 #include <linux/mem_encrypt.h>
 #include <linux/dma-mapping.h>
+#include <asm/kvm_para.h>
 
 /* Override for DMA direct allocation check - ARCH_HAS_FORCE_DMA_UNENCRYPTED */
 bool force_dma_unencrypted(struct device *dev)
 {
 	/*
-	 * For SEV, all DMA must be to unencrypted/shared addresses.
+	 * For SEV and KVM, all DMA must be to unencrypted/shared addresses.
 	 */
-	if (sev_active())
+	if (sev_active() || kvm_mem_protected())
 		return true;
 
 	/*
diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c
index b8c55a2e402d..6f075766bb94 100644
--- a/arch/x86/mm/pat/set_memory.c
+++ b/arch/x86/mm/pat/set_memory.c
@@ -16,6 +16,7 @@
 #include <linux/pci.h>
 #include <linux/vmalloc.h>
 #include <linux/libnvdimm.h>
+#include <linux/kvm_para.h>
 
 #include <asm/e820/api.h>
 #include <asm/processor.h>
@@ -1972,6 +1973,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
 	struct cpa_data cpa;
 	int ret;
 
+	if (kvm_mem_protected()) {
+		unsigned long gfn = __pa(addr) >> PAGE_SHIFT;
+		int call = enc ? KVM_HC_MEM_UNSHARE : KVM_HC_MEM_SHARE;
+		return kvm_hypercall2(call, gfn, numpages);
+	}
+
 	/* Nothing to do if memory encryption is not active */
 	if (!mem_encrypt_active())
 		return 0;
diff --git a/include/uapi/linux/kvm_para.h b/include/uapi/linux/kvm_para.h
index 1a216f32e572..c6d8c988e330 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -30,6 +30,8 @@
 #define KVM_HC_SEND_IPI			10
 #define KVM_HC_SCHED_YIELD		11
 #define KVM_HC_ENABLE_MEM_PROTECTED	12
+#define KVM_HC_MEM_SHARE		13
+#define KVM_HC_MEM_UNSHARE		14
 
 /*
  * hypercalls use architecture specific
-- 
2.26.2