[PATCH 4/6] drivers/virt: pkvm: Hook up mem_encrypt API using pKVM hypercalls
Will Deacon
will at kernel.org
Tue Jul 30 08:11:10 PDT 2024
If we detect the presence of pKVM's SHARE and UNSHARE hypercalls, then
register a backend implementation of the mem_encrypt API so that things
like DMA buffers can be shared appropriately with the host.
Signed-off-by: Will Deacon <will at kernel.org>
---
Documentation/virt/kvm/arm/hypercalls.rst | 50 +++++++++++++++++
drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c | 55 +++++++++++++++++++
include/linux/arm-smccc.h | 14 +++++
3 files changed, 119 insertions(+)
diff --git a/Documentation/virt/kvm/arm/hypercalls.rst b/Documentation/virt/kvm/arm/hypercalls.rst
index 16515eb42149..c42580e71bf8 100644
--- a/Documentation/virt/kvm/arm/hypercalls.rst
+++ b/Documentation/virt/kvm/arm/hypercalls.rst
@@ -66,3 +66,53 @@ Query the memory protection parameters for a pKVM protected virtual machine.
| Return Values: | (int64) | R0 | ``INVALID_PARAMETER (-3)`` on error, else |
| | | | memory protection granule in bytes |
+---------------------+----------+----+---------------------------------------------+
+
+``ARM_SMCCC_KVM_FUNC_MEM_SHARE``
+--------------------------------
+
+Share a region of memory with the KVM host, granting it read, write and execute
+permissions. The size of the region is equal to the memory protection granule
+advertised by ``ARM_SMCCC_KVM_FUNC_HYP_MEMINFO``.
+
++---------------------+-------------------------------------------------------------+
+| Presence: | Optional; pKVM protected guests only. |
++---------------------+-------------------------------------------------------------+
+| Calling convention: | HVC64 |
++---------------------+----------+--------------------------------------------------+
+| Function ID: | (uint32) | 0xC6000003 |
++---------------------+----------+----+---------------------------------------------+
+| Arguments: | (uint64) | R1 | Base IPA of memory region to share |
+| +----------+----+---------------------------------------------+
+| | (uint64) | R2 | Reserved / Must be zero |
+| +----------+----+---------------------------------------------+
+| | (uint64) | R3 | Reserved / Must be zero |
++---------------------+----------+----+---------------------------------------------+
+| Return Values: | (int64) | R0 | ``SUCCESS (0)`` |
+| | | +---------------------------------------------+
+| | | | ``INVALID_PARAMETER (-3)`` |
++---------------------+----------+----+---------------------------------------------+
+
+``ARM_SMCCC_KVM_FUNC_MEM_UNSHARE``
+----------------------------------
+
+Revoke access permission from the KVM host to a memory region previously shared
+with ``ARM_SMCCC_KVM_FUNC_MEM_SHARE``. The size of the region is equal to the
+memory protection granule advertised by ``ARM_SMCCC_KVM_FUNC_HYP_MEMINFO``.
+
++---------------------+-------------------------------------------------------------+
+| Presence: | Optional; pKVM protected guests only. |
++---------------------+-------------------------------------------------------------+
+| Calling convention: | HVC64 |
++---------------------+----------+--------------------------------------------------+
+| Function ID: | (uint32) | 0xC6000004 |
++---------------------+----------+----+---------------------------------------------+
+| Arguments: | (uint64) | R1 | Base IPA of memory region to unshare |
+| +----------+----+---------------------------------------------+
+| | (uint64) | R2 | Reserved / Must be zero |
+| +----------+----+---------------------------------------------+
+| | (uint64) | R3 | Reserved / Must be zero |
++---------------------+----------+----+---------------------------------------------+
+| Return Values: | (int64) | R0 | ``SUCCESS (0)`` |
+| | | +---------------------------------------------+
+| | | | ``INVALID_PARAMETER (-3)`` |
++---------------------+----------+----+---------------------------------------------+
diff --git a/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c b/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c
index a5148701d2f1..8256cf68fd76 100644
--- a/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c
+++ b/drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c
@@ -9,18 +9,72 @@
#include <linux/arm-smccc.h>
#include <linux/array_size.h>
+#include <linux/mem_encrypt.h>
#include <linux/mm.h>
#include <asm/hypervisor.h>
static size_t pkvm_granule;
+static int arm_smccc_do_one_page(u32 func_id, phys_addr_t phys)
+{
+ phys_addr_t end = phys + PAGE_SIZE;
+
+ while (phys < end) {
+ struct arm_smccc_res res;
+
+ arm_smccc_1_1_invoke(func_id, phys, 0, 0, &res);
+ if (res.a0 != SMCCC_RET_SUCCESS)
+ return -EPERM;
+
+ phys += pkvm_granule;
+ }
+
+ return 0;
+}
+
+static int __set_memory_range(u32 func_id, unsigned long start, int numpages)
+{
+ void *addr = (void *)start, *end = addr + numpages * PAGE_SIZE;
+
+ while (addr < end) {
+ int err;
+
+ err = arm_smccc_do_one_page(func_id, virt_to_phys(addr));
+ if (err)
+ return err;
+
+ addr += PAGE_SIZE;
+ }
+
+ return 0;
+}
+
+static int pkvm_set_memory_encrypted(unsigned long addr, int numpages)
+{
+ return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID,
+ addr, numpages);
+}
+
+static int pkvm_set_memory_decrypted(unsigned long addr, int numpages)
+{
+ return __set_memory_range(ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID,
+ addr, numpages);
+}
+
+static const struct arm64_mem_crypt_ops pkvm_crypt_ops = {
+ .encrypt = pkvm_set_memory_encrypted,
+ .decrypt = pkvm_set_memory_decrypted,
+};
+
void pkvm_init_hyp_services(void)
{
int i;
struct arm_smccc_res res;
const u32 funcs[] = {
ARM_SMCCC_KVM_FUNC_HYP_MEMINFO,
+ ARM_SMCCC_KVM_FUNC_MEM_SHARE,
+ ARM_SMCCC_KVM_FUNC_MEM_UNSHARE,
};
for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
@@ -34,4 +88,5 @@ void pkvm_init_hyp_services(void)
return;
pkvm_granule = res.a0;
+ arm64_mem_crypt_ops_register(&pkvm_crypt_ops);
}
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 16b6dcc54e02..9cb7c95920b0 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -116,6 +116,8 @@
#define ARM_SMCCC_KVM_FUNC_FEATURES 0
#define ARM_SMCCC_KVM_FUNC_PTP 1
#define ARM_SMCCC_KVM_FUNC_HYP_MEMINFO 2
+#define ARM_SMCCC_KVM_FUNC_MEM_SHARE 3
+#define ARM_SMCCC_KVM_FUNC_MEM_UNSHARE 4
#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
#define ARM_SMCCC_KVM_NUM_FUNCS 128
@@ -144,6 +146,18 @@
ARM_SMCCC_OWNER_VENDOR_HYP, \
ARM_SMCCC_KVM_FUNC_HYP_MEMINFO)
+#define ARM_SMCCC_VENDOR_HYP_KVM_MEM_SHARE_FUNC_ID \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+ ARM_SMCCC_SMC_64, \
+ ARM_SMCCC_OWNER_VENDOR_HYP, \
+ ARM_SMCCC_KVM_FUNC_MEM_SHARE)
+
+#define ARM_SMCCC_VENDOR_HYP_KVM_MEM_UNSHARE_FUNC_ID \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+ ARM_SMCCC_SMC_64, \
+ ARM_SMCCC_OWNER_VENDOR_HYP, \
+ ARM_SMCCC_KVM_FUNC_MEM_UNSHARE)
+
/* ptp_kvm counter type ID */
#define KVM_PTP_VIRT_COUNTER 0
#define KVM_PTP_PHYS_COUNTER 1
--
2.46.0.rc1.232.g9752f9e123-goog
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