[V3 10/11] KVM: selftests: Add ucall pool based implementation

From: Peter Gonda
Date: Wed Aug 10 2022 - 11:21:55 EST

To add support for encrypted, SEV, guests in the ucall framework
introduce a new "ucall pool" implementation. This was suggested in
the thread on "[RFC PATCH 00/10] KVM: selftests: Add support for
test-selectable ucall implementations". Using a listed as suggested
there doesn't work well because the list is setup using HVAs not GVAs
so use a bitmap + array solution instead to get the same pool of ucall
structs result.

This allows for guests with encryption enabled set up a pool of ucall
structs in the guest's shared memory region.

Suggested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
Signed-off-by: Peter Gonda <pgonda@xxxxxxxxxx>
---
.../selftests/kvm/include/kvm_util_base.h | 2 +
.../selftests/kvm/include/ucall_common.h | 13 +--
.../testing/selftests/kvm/lib/aarch64/ucall.c | 10 +-
tools/testing/selftests/kvm/lib/riscv/ucall.c | 5 +-
tools/testing/selftests/kvm/lib/s390x/ucall.c | 5 +-
.../testing/selftests/kvm/lib/ucall_common.c | 108 +++++++++++++++++-
.../testing/selftests/kvm/lib/x86_64/ucall.c | 6 +-
7 files changed, 131 insertions(+), 18 deletions(-)

diff --git a/tools/testing/selftests/kvm/include/kvm_util_base.h b/tools/testing/selftests/kvm/include/kvm_util_base.h
index 1a84d2d1d85b..baede0d118c5 100644
--- a/tools/testing/selftests/kvm/include/kvm_util_base.h
+++ b/tools/testing/selftests/kvm/include/kvm_util_base.h
@@ -103,6 +103,8 @@ struct kvm_vm {
int stats_fd;
struct kvm_stats_header stats_header;
struct kvm_stats_desc *stats_desc;
+
+ bool use_ucall_pool;
};


diff --git a/tools/testing/selftests/kvm/include/ucall_common.h b/tools/testing/selftests/kvm/include/ucall_common.h
index 63bfc60be995..002a22e1cd1d 100644
--- a/tools/testing/selftests/kvm/include/ucall_common.h
+++ b/tools/testing/selftests/kvm/include/ucall_common.h
@@ -22,6 +22,9 @@ enum {
struct ucall {
uint64_t cmd;
uint64_t args[UCALL_MAX_ARGS];
+
+ /* For ucall pool usage. */
+ struct ucall *hva;
};

void ucall_arch_init(struct kvm_vm *vm, void *arg);
@@ -32,15 +35,9 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu);
void ucall(uint64_t cmd, int nargs, ...);
uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc);

-static inline void ucall_init(struct kvm_vm *vm, void *arg)
-{
- ucall_arch_init(vm, arg);
-}
+void ucall_init(struct kvm_vm *vm, void *arg);

-static inline void ucall_uninit(struct kvm_vm *vm)
-{
- ucall_arch_uninit(vm);
-}
+void ucall_uninit(struct kvm_vm *vm);

#define GUEST_SYNC_ARGS(stage, arg1, arg2, arg3, arg4) \
ucall(UCALL_SYNC, 6, "hello", stage, arg1, arg2, arg3, arg4)
diff --git a/tools/testing/selftests/kvm/lib/aarch64/ucall.c b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
index 132c0e98bf49..ee70531e8e51 100644
--- a/tools/testing/selftests/kvm/lib/aarch64/ucall.c
+++ b/tools/testing/selftests/kvm/lib/aarch64/ucall.c
@@ -81,12 +81,16 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)

if (run->exit_reason == KVM_EXIT_MMIO &&
run->mmio.phys_addr == (uint64_t)ucall_exit_mmio_addr) {
- vm_vaddr_t gva;
+ uint64_t ucall_addr;

TEST_ASSERT(run->mmio.is_write && run->mmio.len == 8,
"Unexpected ucall exit mmio address access");
- memcpy(&gva, run->mmio.data, sizeof(gva));
- return addr_gva2hva(vcpu->vm, gva);
+ memcpy(&ucall_addr, run->mmio.data, sizeof(ucall_addr));
+
+ if (vcpu->vm->use_ucall_pool)
+ return (void *)ucall_addr;
+ else
+ return addr_gva2hva(vcpu->vm, ucall_addr);
}

return NULL;
diff --git a/tools/testing/selftests/kvm/lib/riscv/ucall.c b/tools/testing/selftests/kvm/lib/riscv/ucall.c
index 37e091d4366e..4bb5616df29f 100644
--- a/tools/testing/selftests/kvm/lib/riscv/ucall.c
+++ b/tools/testing/selftests/kvm/lib/riscv/ucall.c
@@ -59,7 +59,10 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
run->riscv_sbi.extension_id == KVM_RISCV_SELFTESTS_SBI_EXT) {
switch (run->riscv_sbi.function_id) {
case KVM_RISCV_SELFTESTS_SBI_UCALL:
- return addr_gva2hva(vcpu->vm, run->riscv_sbi.args[0]);
+ if (vcpu->vm->use_ucall_pool)
+ return (void *)run->riscv_sbi.args[0];
+ else
+ return addr_gva2hva(vcpu->vm, run->riscv_sbi.args[0]);
case KVM_RISCV_SELFTESTS_SBI_UNEXP:
vcpu_dump(stderr, vcpu, 2);
TEST_ASSERT(0, "Unexpected trap taken by guest");
diff --git a/tools/testing/selftests/kvm/lib/s390x/ucall.c b/tools/testing/selftests/kvm/lib/s390x/ucall.c
index 0f695a031d35..b24c6649877a 100644
--- a/tools/testing/selftests/kvm/lib/s390x/ucall.c
+++ b/tools/testing/selftests/kvm/lib/s390x/ucall.c
@@ -30,7 +30,10 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
(run->s390_sieic.ipb >> 16) == 0x501) {
int reg = run->s390_sieic.ipa & 0xf;

- return addr_gva2hva(vcpu->vm, run->s.regs.gprs[reg]);
+ if (vcpu->vm->use_ucall_pool)
+ return (void *)run->s.regs.gprs[reg];
+ else
+ return addr_gva2hva(vcpu->vm, run->s.regs.gprs[reg]);
}
return NULL;
}
diff --git a/tools/testing/selftests/kvm/lib/ucall_common.c b/tools/testing/selftests/kvm/lib/ucall_common.c
index ced480860746..b6502a9420c4 100644
--- a/tools/testing/selftests/kvm/lib/ucall_common.c
+++ b/tools/testing/selftests/kvm/lib/ucall_common.c
@@ -1,22 +1,122 @@
// SPDX-License-Identifier: GPL-2.0-only
#include "kvm_util.h"
+#include "linux/types.h"
+#include "linux/bitmap.h"
+#include "linux/atomic.h"
+
+struct ucall_header {
+ DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
+ struct ucall ucalls[KVM_MAX_VCPUS];
+};
+
+static bool use_ucall_pool;
+static struct ucall_header *ucall_pool;
+
+void ucall_init(struct kvm_vm *vm, void *arg)
+{
+ struct ucall *uc;
+ struct ucall_header *hdr;
+ vm_vaddr_t vaddr;
+ int i;
+
+ use_ucall_pool = vm->use_ucall_pool;
+ sync_global_to_guest(vm, use_ucall_pool);
+ if (!use_ucall_pool)
+ goto out;
+
+ TEST_ASSERT(!ucall_pool, "Only a single encrypted guest at a time for ucalls.");
+ vaddr = vm_vaddr_alloc_shared(vm, sizeof(*hdr), vm->page_size);
+ hdr = (struct ucall_header *)addr_gva2hva(vm, vaddr);
+ memset(hdr, 0, sizeof(*hdr));
+
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ uc = &hdr->ucalls[i];
+ uc->hva = uc;
+ }
+
+ ucall_pool = (struct ucall_header *)vaddr;
+ sync_global_to_guest(vm, ucall_pool);
+
+out:
+ ucall_arch_init(vm, arg);
+}
+
+void ucall_uninit(struct kvm_vm *vm)
+{
+ use_ucall_pool = false;
+ ucall_pool = NULL;
+
+ if (!vm->memcrypt.encrypted) {
+ sync_global_to_guest(vm, use_ucall_pool);
+ sync_global_to_guest(vm, ucall_pool);
+ }
+
+ ucall_arch_uninit(vm);
+}
+
+static struct ucall *ucall_alloc(void)
+{
+ struct ucall *uc = NULL;
+ int i;
+
+ if (!use_ucall_pool)
+ goto out;
+
+ for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+ if (!atomic_test_and_set_bit(i, ucall_pool->in_use)) {
+ uc = &ucall_pool->ucalls[i];
+ memset(uc->args, 0, sizeof(uc->args));
+ break;
+ }
+ }
+out:
+ return uc;
+}
+
+static inline size_t uc_pool_idx(struct ucall *uc)
+{
+ return uc->hva - ucall_pool->ucalls;
+}
+
+static void ucall_free(struct ucall *uc)
+{
+ if (!use_ucall_pool)
+ return;
+
+ clear_bit(uc_pool_idx(uc), ucall_pool->in_use);
+}

void ucall(uint64_t cmd, int nargs, ...)
{
- struct ucall uc = {};
+ struct ucall *uc;
+ struct ucall tmp = {};
va_list va;
int i;

- WRITE_ONCE(uc.cmd, cmd);
+ uc = ucall_alloc();
+ if (!uc)
+ uc = &tmp;
+
+ WRITE_ONCE(uc->cmd, cmd);

nargs = min(nargs, UCALL_MAX_ARGS);

va_start(va, nargs);
for (i = 0; i < nargs; ++i)
- WRITE_ONCE(uc.args[i], va_arg(va, uint64_t));
+ WRITE_ONCE(uc->args[i], va_arg(va, uint64_t));
va_end(va);

- ucall_arch_do_ucall((vm_vaddr_t)&uc);
+ /*
+ * When using the ucall pool implementation the @hva member of the ucall
+ * structs in the pool has been initialized to the hva of the ucall
+ * object.
+ */
+ if (use_ucall_pool)
+ ucall_arch_do_ucall((vm_vaddr_t)uc->hva);
+ else
+ ucall_arch_do_ucall((vm_vaddr_t)uc);
+
+ ucall_free(uc);
}

uint64_t get_ucall(struct kvm_vcpu *vcpu, struct ucall *uc)
diff --git a/tools/testing/selftests/kvm/lib/x86_64/ucall.c b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
index ead9946399ab..07c1bc41fa5c 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/ucall.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/ucall.c
@@ -30,7 +30,11 @@ void *ucall_arch_get_ucall(struct kvm_vcpu *vcpu)
struct kvm_regs regs;

vcpu_regs_get(vcpu, &regs);
- return addr_gva2hva(vcpu->vm, regs.rdi);
+
+ if (vcpu->vm->use_ucall_pool)
+ return (void *)regs.rdi;
+ else
+ return addr_gva2hva(vcpu->vm, regs.rdi);
}
return NULL;
}
--
2.37.1.559.g78731f0fdb-goog