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

Kirill A. Shutemov
2020-05-22T12:52:29Z

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@linux.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