[RFCv2 03/13] x86/kvm: Make DMA pages shared

Kirill A. Shutemov
2021-04-16T15:41:47Z

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 | 10 ++++++++++
include/uapi/linux/kvm_para.h | 1 +
4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 2b4ce1722dbd..d197b3beb904 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -811,6 +811,7 @@ config KVM_GUEST
select PARAVIRT_CLOCK
select ARCH_CPUIDLE_HALTPOLL
select X86_HV_CALLBACK_VECTOR
+ 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 dd791352f73f..6bf0718bb72a 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-direct.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 16f878c26667..4b312d80033d 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>
@@ -1977,6 +1978,15 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
struct cpa_data cpa;
int ret;

+ if (kvm_mem_protected()) {
+ /* TODO: Unsharing memory back */
+ if (WARN_ON_ONCE(enc))
+ return -ENOSYS;
+
+ return kvm_hypercall2(KVM_HC_MEM_SHARE,
+ __pa(addr) >> PAGE_SHIFT, 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..09d36683ee0a 100644
--- a/include/uapi/linux/kvm_para.h
+++ b/include/uapi/linux/kvm_para.h
@@ -30,6 +30,7 @@
#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

/*
* hypercalls use architecture specific
--
2.26.3