* [PATCH RFC v3 21/43] KVM: selftests: Test conversion flow when INIT_SHARED
From: Ackerley Tng @ 2026-03-13 6:13 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Add a test case to verify that conversions between private and shared
memory work correctly when the memory is initially created as shared.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/guest_memfd_conversions_test.c | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
index 48265215f218e..438937980f040 100644
--- a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
@@ -95,6 +95,12 @@ static void __gmem_conversions_##test(test_data_t *t, int nr_pages) \
#define GMEM_CONVERSION_TEST_INIT_PRIVATE(test) \
__GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
+#define __GMEM_CONVERSION_TEST_INIT_SHARED(test, __nr_pages) \
+ GMEM_CONVERSION_TEST(test, __nr_pages, GUEST_MEMFD_FLAG_INIT_SHARED)
+
+#define GMEM_CONVERSION_TEST_INIT_SHARED(test) \
+ __GMEM_CONVERSION_TEST_INIT_SHARED(test, 1)
+
struct guest_check_data {
void *mem;
char expected_val;
@@ -186,6 +192,12 @@ GMEM_CONVERSION_TEST_INIT_PRIVATE(init_private)
test_convert_to_private(t, 0, 'C', 'E');
}
+GMEM_CONVERSION_TEST_INIT_SHARED(init_shared)
+{
+ test_shared(t, 0, 0, 'A', 'B');
+ test_convert_to_private(t, 0, 'B', 'C');
+ test_convert_to_shared(t, 0, 'C', 'D', 'E');
+}
int main(int argc, char *argv[])
{
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 20/43] KVM: selftests: Test basic single-page conversion flow
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Add a selftest for the guest_memfd memory attribute conversion ioctls.
The test starts the guest_memfd as all-private (the default state), and
verifies the basic flow of converting a single page to shared and then back
to private.
Add infrastructure that supports extensions to other conversion flow
tests. This infrastructure will be used in upcoming patches for other
conversion tests.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../selftests/kvm/guest_memfd_conversions_test.c | 199 +++++++++++++++++++++
2 files changed, 200 insertions(+)
diff --git a/tools/testing/selftests/kvm/Makefile.kvm b/tools/testing/selftests/kvm/Makefile.kvm
index dc68371f76a33..0e2a9adfca57e 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -147,6 +147,7 @@ TEST_GEN_PROGS_x86 += access_tracking_perf_test
TEST_GEN_PROGS_x86 += coalesced_io_test
TEST_GEN_PROGS_x86 += dirty_log_perf_test
TEST_GEN_PROGS_x86 += guest_memfd_test
+TEST_GEN_PROGS_x86 += guest_memfd_conversions_test
TEST_GEN_PROGS_x86 += hardware_disable_test
TEST_GEN_PROGS_x86 += memslot_modification_stress_test
TEST_GEN_PROGS_x86 += memslot_perf_test
diff --git a/tools/testing/selftests/kvm/guest_memfd_conversions_test.c b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
new file mode 100644
index 0000000000000..48265215f218e
--- /dev/null
+++ b/tools/testing/selftests/kvm/guest_memfd_conversions_test.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2024, Google LLC.
+ */
+#include <sys/mman.h>
+#include <unistd.h>
+
+#include <linux/align.h>
+#include <linux/kvm.h>
+#include <linux/sizes.h>
+
+#include "kvm_util.h"
+#include "kselftest_harness.h"
+#include "test_util.h"
+#include "ucall_common.h"
+
+FIXTURE(gmem_conversions) {
+ struct kvm_vcpu *vcpu;
+ int gmem_fd;
+ /* HVA of the first byte of the memory mmap()-ed from gmem_fd. */
+ char *mem;
+};
+
+typedef FIXTURE_DATA(gmem_conversions) test_data_t;
+
+FIXTURE_SETUP(gmem_conversions) { }
+
+static uint64_t page_size;
+
+static void guest_do_rmw(void);
+#define GUEST_MEMFD_SHARING_TEST_GVA 0x90000000ULL
+
+/*
+ * Defer setup until the individual test is invoked so that tests can specify
+ * the number of pages and flags for the guest_memfd instance.
+ */
+static void gmem_conversions_do_setup(test_data_t *t, int nr_pages,
+ int gmem_flags)
+{
+ const struct vm_shape shape = {
+ .mode = VM_MODE_DEFAULT,
+ .type = KVM_X86_SW_PROTECTED_VM,
+ };
+ /*
+ * Use high GPA above APIC_DEFAULT_PHYS_BASE to avoid clashing with
+ * APIC_DEFAULT_PHYS_BASE.
+ */
+ const uint64_t gpa = SZ_4G;
+ const uint32_t slot = 1;
+ struct kvm_vm *vm;
+
+ vm = __vm_create_shape_with_one_vcpu(shape, &t->vcpu, nr_pages, guest_do_rmw);
+
+ vm_mem_add(vm, VM_MEM_SRC_SHMEM, gpa, slot, nr_pages,
+ KVM_MEM_GUEST_MEMFD, -1, 0, gmem_flags);
+
+ t->gmem_fd = kvm_slot_to_fd(vm, slot);
+ t->mem = addr_gpa2hva(vm, gpa);
+ virt_map(vm, GUEST_MEMFD_SHARING_TEST_GVA, gpa, nr_pages);
+}
+
+static void gmem_conversions_do_teardown(test_data_t *t)
+{
+ /* No need to close gmem_fd, it's owned by the VM structure. */
+ kvm_vm_free(t->vcpu->vm);
+}
+
+FIXTURE_TEARDOWN(gmem_conversions)
+{
+ gmem_conversions_do_teardown(self);
+}
+
+/*
+ * In these test definition macros, __nr_pages and nr_pages is used to set up
+ * the total number of pages in the guest_memfd under test. This will be
+ * available in the test definitions as nr_pages.
+ */
+
+#define __GMEM_CONVERSION_TEST(test, __nr_pages, flags) \
+static void __gmem_conversions_##test(test_data_t *t, int nr_pages); \
+ \
+TEST_F(gmem_conversions, test) \
+{ \
+ gmem_conversions_do_setup(self, __nr_pages, flags); \
+ __gmem_conversions_##test(self, __nr_pages); \
+} \
+static void __gmem_conversions_##test(test_data_t *t, int nr_pages) \
+
+#define GMEM_CONVERSION_TEST(test, __nr_pages, flags) \
+ __GMEM_CONVERSION_TEST(test, __nr_pages, (flags) | GUEST_MEMFD_FLAG_MMAP)
+
+#define __GMEM_CONVERSION_TEST_INIT_PRIVATE(test, __nr_pages) \
+ GMEM_CONVERSION_TEST(test, __nr_pages, 0)
+
+#define GMEM_CONVERSION_TEST_INIT_PRIVATE(test) \
+ __GMEM_CONVERSION_TEST_INIT_PRIVATE(test, 1)
+
+struct guest_check_data {
+ void *mem;
+ char expected_val;
+ char write_val;
+};
+static struct guest_check_data guest_data;
+
+static void guest_do_rmw(void)
+{
+ for (;;) {
+ char *mem = READ_ONCE(guest_data.mem);
+
+ GUEST_ASSERT_EQ(READ_ONCE(*mem), READ_ONCE(guest_data.expected_val));
+ WRITE_ONCE(*mem, READ_ONCE(guest_data.write_val));
+
+ GUEST_SYNC(0);
+ }
+}
+
+static void run_guest_do_rmw(struct kvm_vcpu *vcpu, loff_t pgoff,
+ char expected_val, char write_val)
+{
+ struct ucall uc;
+ int r;
+
+ guest_data.mem = (void *)GUEST_MEMFD_SHARING_TEST_GVA + pgoff * page_size;
+ guest_data.expected_val = expected_val;
+ guest_data.write_val = write_val;
+ sync_global_to_guest(vcpu->vm, guest_data);
+
+ do {
+ r = __vcpu_run(vcpu);
+ } while (r == -1 && errno == EINTR);
+
+ TEST_ASSERT_EQ(r, 0);
+
+ switch (get_ucall(vcpu, &uc)) {
+ case UCALL_ABORT:
+ REPORT_GUEST_ASSERT(uc);
+ case UCALL_SYNC:
+ break;
+ default:
+ TEST_FAIL("Unexpected ucall %lu", uc.cmd);
+ }
+}
+
+static void host_do_rmw(char *mem, loff_t pgoff, char expected_val,
+ char write_val)
+{
+ TEST_ASSERT_EQ(READ_ONCE(mem[pgoff * page_size]), expected_val);
+ WRITE_ONCE(mem[pgoff * page_size], write_val);
+}
+
+static void test_private(test_data_t *t, loff_t pgoff, char starting_val,
+ char write_val)
+{
+ TEST_EXPECT_SIGBUS(WRITE_ONCE(t->mem[pgoff * page_size], write_val));
+ run_guest_do_rmw(t->vcpu, pgoff, starting_val, write_val);
+ TEST_EXPECT_SIGBUS(READ_ONCE(t->mem[pgoff * page_size]));
+}
+
+static void test_convert_to_private(test_data_t *t, loff_t pgoff,
+ char starting_val, char write_val)
+{
+ gmem_set_private(t->gmem_fd, pgoff * page_size, page_size);
+ test_private(t, pgoff, starting_val, write_val);
+}
+
+static void test_shared(test_data_t *t, loff_t pgoff, char starting_val,
+ char host_write_val, char write_val)
+{
+ host_do_rmw(t->mem, pgoff, starting_val, host_write_val);
+ run_guest_do_rmw(t->vcpu, pgoff, host_write_val, write_val);
+ TEST_ASSERT_EQ(READ_ONCE(t->mem[pgoff * page_size]), write_val);
+}
+
+static void test_convert_to_shared(test_data_t *t, loff_t pgoff,
+ char starting_val, char host_write_val,
+ char write_val)
+{
+ gmem_set_shared(t->gmem_fd, pgoff * page_size, page_size);
+ test_shared(t, pgoff, starting_val, host_write_val, write_val);
+}
+
+GMEM_CONVERSION_TEST_INIT_PRIVATE(init_private)
+{
+ test_private(t, 0, 0, 'A');
+ test_convert_to_shared(t, 0, 'A', 'B', 'C');
+ test_convert_to_private(t, 0, 'C', 'E');
+}
+
+
+int main(int argc, char *argv[])
+{
+ TEST_REQUIRE(kvm_check_cap(KVM_CAP_VM_TYPES) & BIT(KVM_X86_SW_PROTECTED_VM));
+ TEST_REQUIRE(kvm_check_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES) &
+ KVM_MEMORY_ATTRIBUTE_PRIVATE);
+
+ page_size = getpagesize();
+
+ return test_harness_run(argc, argv);
+}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 19/43] KVM: selftests: Test using guest_memfd for guest private memory
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Add a selftest to verify that a memory region backed by a guest_memfd
can be used as private guest memory. This is a key use case for
confidential computing guests where the host should not have access to the
guest's memory contents.
The new test, test_guest_private_mem, creates a protected VM, maps a
guest_memfd into the guest's address space, and then marks the region as
private. The guest code then writes to and reads from this private memory
region to verify it is accessible.
To better distinguish between the test cases, rename the existing test
that verifies shared host/guest access from test_guest_memfd_guest to
test_guest_shared_mem.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/guest_memfd_test.c | 57 ++++++++++++++++++++++++--
1 file changed, 53 insertions(+), 4 deletions(-)
diff --git a/tools/testing/selftests/kvm/guest_memfd_test.c b/tools/testing/selftests/kvm/guest_memfd_test.c
index cc329b57ce2e9..10b57fd4fa9ba 100644
--- a/tools/testing/selftests/kvm/guest_memfd_test.c
+++ b/tools/testing/selftests/kvm/guest_memfd_test.c
@@ -406,7 +406,7 @@ static void test_guest_memfd(unsigned long vm_type)
kvm_vm_free(vm);
}
-static void guest_code(uint8_t *mem, uint64_t size)
+static void guest_code_test_guest_shared_mem(uint8_t *mem, uint64_t size)
{
size_t i;
@@ -418,7 +418,7 @@ static void guest_code(uint8_t *mem, uint64_t size)
GUEST_DONE();
}
-static void test_guest_memfd_guest(void)
+static void test_guest_shared_mem(void)
{
/*
* Skip the first 4gb and slot0. slot0 maps <1gb and is used to back
@@ -437,7 +437,8 @@ static void test_guest_memfd_guest(void)
if (!kvm_check_cap(KVM_CAP_GUEST_MEMFD_FLAGS))
return;
- vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1, guest_code);
+ vm = __vm_create_shape_with_one_vcpu(VM_SHAPE_DEFAULT, &vcpu, 1,
+ guest_code_test_guest_shared_mem);
TEST_ASSERT(vm_check_cap(vm, KVM_CAP_GUEST_MEMFD_FLAGS) & GUEST_MEMFD_FLAG_MMAP,
"Default VM type should support MMAP, supported flags = 0x%x",
@@ -469,6 +470,53 @@ static void test_guest_memfd_guest(void)
kvm_vm_free(vm);
}
+static void guest_code_test_guest_private_mem(uint8_t *mem)
+{
+ WRITE_ONCE(mem[0], 0xff);
+ GUEST_ASSERT_EQ(READ_ONCE(mem[0]), 0xff);
+
+ GUEST_DONE();
+}
+
+static void test_guest_private_mem(void)
+{
+ const struct vm_shape shape = {
+ .mode = VM_MODE_DEFAULT,
+ .type = KVM_X86_SW_PROTECTED_VM,
+ };
+ /*
+ * Skip the first 4gb and slot0. slot0 maps <1gb and is used to back
+ * the guest's code, stack, and page tables, and low memory contains
+ * the PCI hole and other MMIO regions that need to be avoided.
+ */
+ const uint64_t gpa = SZ_4G;
+ const int slot = 1;
+
+ struct kvm_vcpu *vcpu;
+ struct kvm_vm *vm;
+ size_t npages;
+ int fd;
+
+ npages = page_size / getpagesize();
+ vm = __vm_create_shape_with_one_vcpu(shape, &vcpu, npages,
+ guest_code_test_guest_private_mem);
+
+ fd = vm_create_guest_memfd(vm, page_size, 0);
+ vm_mem_add(vm, VM_MEM_SRC_SHMEM, gpa, slot, npages, KVM_MEM_GUEST_MEMFD,
+ fd, 0, 0);
+
+ virt_map(vm, gpa, gpa, npages);
+ vm_mem_set_private(vm, gpa, page_size);
+
+ vcpu_args_set(vcpu, 1, gpa);
+ vcpu_run(vcpu);
+
+ TEST_ASSERT_EQ(get_ucall(vcpu, NULL), UCALL_DONE);
+
+ close(fd);
+ kvm_vm_free(vm);
+}
+
int main(int argc, char *argv[])
{
unsigned long vm_types, vm_type;
@@ -488,5 +536,6 @@ int main(int argc, char *argv[])
for_each_set_bit(vm_type, &vm_types, BITS_PER_TYPE(vm_types))
test_guest_memfd(vm_type);
- test_guest_memfd_guest();
+ test_guest_shared_mem();
+ test_guest_private_mem();
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 18/43] KVM: selftests: Add helpers for calling ioctls on guest_memfd
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Add helper functions to kvm_util.h to support calling ioctls, specifically
KVM_SET_MEMORY_ATTRIBUTES2, on a guest_memfd file descriptor.
Introduce gmem_ioctl() and __gmem_ioctl() macros, modeled after the
existing vm_ioctl() helpers, to provide a standard way to call ioctls
on a guest_memfd.
Add gmem_set_memory_attributes() and its derivatives (gmem_set_private(),
gmem_set_shared()) to set memory attributes on a guest_memfd region.
Also provide "__" variants that return the ioctl error code instead of
aborting the test. These helpers will be used by upcoming guest_memfd
tests.
To avoid code duplication, factor out the check for supported memory
attributes into a new macro, TEST_ASSERT_SUPPORTED_ATTRIBUTES, and use
it in both the existing vm_set_memory_attributes() and the new
gmem_set_memory_attributes() helpers.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/include/kvm_util.h | 89 ++++++++++++++++++++++++--
1 file changed, 82 insertions(+), 7 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index fc55ad3c67485..1c0f41bf847d0 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -333,6 +333,16 @@ static inline bool kvm_has_cap(long cap)
TEST_ASSERT(!ret, __KVM_IOCTL_ERROR(#cmd, ret)); \
})
+#define __gmem_ioctl(gmem_fd, cmd, arg) \
+ kvm_do_ioctl(gmem_fd, cmd, arg)
+
+#define gmem_ioctl(gmem_fd, cmd, arg) \
+({ \
+ int ret = __gmem_ioctl(gmem_fd, cmd, arg); \
+ \
+ TEST_ASSERT(!ret, __KVM_IOCTL_ERROR(#cmd, ret)); \
+})
+
static __always_inline void static_assert_is_vm(struct kvm_vm *vm) { }
#define __vm_ioctl(vm, cmd, arg) \
@@ -417,6 +427,14 @@ static inline void vm_enable_cap(struct kvm_vm *vm, uint32_t cap, uint64_t arg0)
vm_ioctl(vm, KVM_ENABLE_CAP, &enable_cap);
}
+/*
+ * KVM_SET_MEMORY_ATTRIBUTES overwrites _all_ attributes. These flows need
+ * significant enhancements to support multiple attributes.
+ */
+#define TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes) \
+ TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE, \
+ "Update me to support multiple attributes!")
+
static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
uint64_t size, uint64_t attributes)
{
@@ -427,12 +445,7 @@ static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
.flags = 0,
};
- /*
- * KVM_SET_MEMORY_ATTRIBUTES2 overwrites _all_ attributes. These flows
- * need significant enhancements to support multiple attributes.
- */
- TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE,
- "Update me to support multiple attributes!");
+ TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes);
__TEST_REQUIRE(kvm_check_cap(KVM_CAP_MEMORY_ATTRIBUTES2) > 0,
"No valid attributes for VM fd ioctl!");
@@ -440,7 +453,6 @@ static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
}
-
static inline void vm_mem_set_private(struct kvm_vm *vm, uint64_t gpa,
uint64_t size)
{
@@ -453,6 +465,69 @@ static inline void vm_mem_set_shared(struct kvm_vm *vm, uint64_t gpa,
vm_set_memory_attributes(vm, gpa, size, 0);
}
+static inline int __gmem_set_memory_attributes(int fd, loff_t offset,
+ uint64_t size,
+ uint64_t attributes,
+ loff_t *error_offset)
+{
+ struct kvm_memory_attributes2 attr = {
+ .attributes = attributes,
+ .offset = offset,
+ .size = size,
+ .flags = 0,
+ };
+ int r;
+
+ TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes);
+
+ r = __gmem_ioctl(fd, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
+ if (r)
+ *error_offset = attr.error_offset;
+ return r;
+}
+
+static inline int __gmem_set_private(int fd, loff_t offset, uint64_t size,
+ loff_t *error_offset)
+{
+ return __gmem_set_memory_attributes(fd, offset, size,
+ KVM_MEMORY_ATTRIBUTE_PRIVATE,
+ error_offset);
+}
+
+static inline int __gmem_set_shared(int fd, loff_t offset, uint64_t size,
+ loff_t *error_offset)
+{
+ return __gmem_set_memory_attributes(fd, offset, size, 0, error_offset);
+}
+
+static inline void gmem_set_memory_attributes(int fd, loff_t offset,
+ uint64_t size, uint64_t attributes)
+{
+ struct kvm_memory_attributes2 attr = {
+ .attributes = attributes,
+ .offset = offset,
+ .size = size,
+ .flags = 0,
+ };
+
+ TEST_ASSERT_SUPPORTED_ATTRIBUTES(attributes);
+
+ __TEST_REQUIRE(kvm_check_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES) > 0,
+ "No valid attributes for guest_memfd ioctl!");
+
+ gmem_ioctl(fd, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
+}
+
+static inline void gmem_set_private(int fd, loff_t offset, uint64_t size)
+{
+ gmem_set_memory_attributes(fd, offset, size, KVM_MEMORY_ATTRIBUTE_PRIVATE);
+}
+
+static inline void gmem_set_shared(int fd, loff_t offset, uint64_t size)
+{
+ gmem_set_memory_attributes(fd, offset, size, 0);
+}
+
void vm_guest_mem_fallocate(struct kvm_vm *vm, uint64_t gpa, uint64_t size,
bool punch_hole);
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 17/43] KVM: selftests: Update framework to use KVM_SET_MEMORY_ATTRIBUTES2
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Update KVM selftest framework to use KVM_SET_MEMORY_ATTRIBUTES2 and the
accompanying struct kvm_memory_attributes2.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/include/kvm_util.h | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index caca482aad859..fc55ad3c67485 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -420,7 +420,7 @@ static inline void vm_enable_cap(struct kvm_vm *vm, uint32_t cap, uint64_t arg0)
static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
uint64_t size, uint64_t attributes)
{
- struct kvm_memory_attributes attr = {
+ struct kvm_memory_attributes2 attr = {
.attributes = attributes,
.address = gpa,
.size = size,
@@ -428,13 +428,16 @@ static inline void vm_set_memory_attributes(struct kvm_vm *vm, uint64_t gpa,
};
/*
- * KVM_SET_MEMORY_ATTRIBUTES overwrites _all_ attributes. These flows
+ * KVM_SET_MEMORY_ATTRIBUTES2 overwrites _all_ attributes. These flows
* need significant enhancements to support multiple attributes.
*/
TEST_ASSERT(!attributes || attributes == KVM_MEMORY_ATTRIBUTE_PRIVATE,
"Update me to support multiple attributes!");
- vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES, &attr);
+ __TEST_REQUIRE(kvm_check_cap(KVM_CAP_MEMORY_ATTRIBUTES2) > 0,
+ "No valid attributes for VM fd ioctl!");
+
+ vm_ioctl(vm, KVM_SET_MEMORY_ATTRIBUTES2, &attr);
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 16/43] KVM: selftests: Add selftests global for guest memory attributes capability
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Add a global variable, kvm_has_gmem_attributes, to make the result of
checking for KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES available to all tests.
kvm_has_gmem_attributes is true if guest_memfd tracks memory attributes, as
opposed to VM-level tracking.
This global variable is synced to the guest for testing convenience, to
avoid introducing subtle bugs when host/guest state is desynced.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/include/test_util.h | 2 ++
tools/testing/selftests/kvm/lib/kvm_util.c | 5 +++++
2 files changed, 7 insertions(+)
diff --git a/tools/testing/selftests/kvm/include/test_util.h b/tools/testing/selftests/kvm/include/test_util.h
index b4872ba8ed124..2871a42928471 100644
--- a/tools/testing/selftests/kvm/include/test_util.h
+++ b/tools/testing/selftests/kvm/include/test_util.h
@@ -113,6 +113,8 @@ struct guest_random_state {
extern uint32_t guest_random_seed;
extern struct guest_random_state guest_rng;
+extern bool kvm_has_gmem_attributes;
+
struct guest_random_state new_guest_random_state(uint32_t seed);
uint32_t guest_random_u32(struct guest_random_state *state);
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 82d6945efa29a..404efb5318f09 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -24,6 +24,8 @@ uint32_t guest_random_seed;
struct guest_random_state guest_rng;
static uint32_t last_guest_seed;
+bool kvm_has_gmem_attributes;
+
static size_t vcpu_mmap_sz(void);
int __open_path_or_exit(const char *path, int flags, const char *enoent_help)
@@ -521,6 +523,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus,
}
guest_rng = new_guest_random_state(guest_random_seed);
sync_global_to_guest(vm, guest_rng);
+ sync_global_to_guest(vm, kvm_has_gmem_attributes);
kvm_arch_vm_post_create(vm, nr_runnable_vcpus);
@@ -2365,6 +2368,8 @@ void __attribute((constructor)) kvm_selftest_init(void)
guest_random_seed = last_guest_seed = random();
pr_info("Random seed: 0x%x\n", guest_random_seed);
+ kvm_has_gmem_attributes = kvm_has_cap(KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES);
+
kvm_selftest_arch_init();
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 15/43] KVM: selftests: Add support for mmap() on guest_memfd in core library
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Accept gmem_flags in vm_mem_add() to be able to create a guest_memfd within
vm_mem_add().
When vm_mem_add() is used to set up a guest_memfd for a memslot, set up the
provided (or created) gmem_fd as the fd for the user memory region. This
makes it available to be mmap()-ed from just like fds from other memory
sources. mmap() from guest_memfd using the provided gmem_flags and
gmem_offset.
Add a kvm_slot_to_fd() helper to provide convenient access to the file
descriptor of a memslot.
Update existing callers of vm_mem_add() to pass 0 for gmem_flags to
preserve existing behavior.
Signed-off-by: Sean Christopherson <seanjc@google.com>
[For guest_memfds, mmap() using gmem_offset instead of 0 all the time.]
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
tools/testing/selftests/kvm/include/kvm_util.h | 7 ++++++-
tools/testing/selftests/kvm/lib/kvm_util.c | 19 +++++++++++--------
.../selftests/kvm/x86/private_mem_conversions_test.c | 2 +-
3 files changed, 18 insertions(+), 10 deletions(-)
diff --git a/tools/testing/selftests/kvm/include/kvm_util.h b/tools/testing/selftests/kvm/include/kvm_util.h
index 8b39cb919f4fc..caca482aad859 100644
--- a/tools/testing/selftests/kvm/include/kvm_util.h
+++ b/tools/testing/selftests/kvm/include/kvm_util.h
@@ -701,7 +701,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
uint32_t flags);
void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
uint64_t gpa, uint32_t slot, uint64_t npages, uint32_t flags,
- int guest_memfd_fd, uint64_t guest_memfd_offset);
+ int gmem_fd, uint64_t gmem_offset, uint64_t gmem_flags);
#ifndef vm_arch_has_protected_memory
static inline bool vm_arch_has_protected_memory(struct kvm_vm *vm)
@@ -735,6 +735,11 @@ void *addr_gva2hva(struct kvm_vm *vm, vm_vaddr_t gva);
vm_paddr_t addr_hva2gpa(struct kvm_vm *vm, void *hva);
void *addr_gpa2alias(struct kvm_vm *vm, vm_paddr_t gpa);
+static inline int kvm_slot_to_fd(struct kvm_vm *vm, uint32_t slot)
+{
+ return memslot2region(vm, slot)->fd;
+}
+
#ifndef vcpu_arch_put_guest
#define vcpu_arch_put_guest(mem, val) do { (mem) = (val); } while (0)
#endif
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 3b64fbadcd88d..82d6945efa29a 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -979,12 +979,13 @@ void vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flags
/* FIXME: This thing needs to be ripped apart and rewritten. */
void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
uint64_t gpa, uint32_t slot, uint64_t npages, uint32_t flags,
- int gmem_fd, uint64_t gmem_offset)
+ int gmem_fd, uint64_t gmem_offset, uint64_t gmem_flags)
{
int ret;
struct userspace_mem_region *region;
size_t backing_src_pagesz = get_backing_src_pagesz(src_type);
size_t mem_size = npages * vm->page_size;
+ off_t mmap_offset = 0;
size_t alignment;
TEST_REQUIRE_SET_USER_MEMORY_REGION2();
@@ -1063,8 +1064,6 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
if (flags & KVM_MEM_GUEST_MEMFD) {
if (gmem_fd < 0) {
- uint32_t gmem_flags = 0;
-
TEST_ASSERT(!gmem_offset,
"Offset must be zero when creating new guest_memfd");
gmem_fd = vm_create_guest_memfd(vm, mem_size, gmem_flags);
@@ -1085,13 +1084,17 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
}
region->fd = -1;
- if (backing_src_is_shared(src_type))
+ if (flags & KVM_MEM_GUEST_MEMFD && gmem_flags & GUEST_MEMFD_FLAG_MMAP) {
+ region->fd = kvm_dup(gmem_fd);
+ mmap_offset = gmem_offset;
+ } else if (backing_src_is_shared(src_type)) {
region->fd = kvm_memfd_alloc(region->mmap_size,
src_type == VM_MEM_SRC_SHARED_HUGETLB);
+ }
- region->mmap_start = kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
- vm_mem_backing_src_alias(src_type)->flag,
- region->fd);
+ region->mmap_start = __kvm_mmap(region->mmap_size, PROT_READ | PROT_WRITE,
+ vm_mem_backing_src_alias(src_type)->flag,
+ region->fd, mmap_offset);
TEST_ASSERT(!is_backing_src_hugetlb(src_type) ||
region->mmap_start == align_ptr_up(region->mmap_start, backing_src_pagesz),
@@ -1152,7 +1155,7 @@ void vm_userspace_mem_region_add(struct kvm_vm *vm,
uint64_t gpa, uint32_t slot, uint64_t npages,
uint32_t flags)
{
- vm_mem_add(vm, src_type, gpa, slot, npages, flags, -1, 0);
+ vm_mem_add(vm, src_type, gpa, slot, npages, flags, -1, 0, 0);
}
/*
diff --git a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
index 1969f4ab9b280..41f6b38f04071 100644
--- a/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86/private_mem_conversions_test.c
@@ -399,7 +399,7 @@ static void test_mem_conversions(enum vm_mem_backing_src_type src_type, uint32_t
for (i = 0; i < nr_memslots; i++)
vm_mem_add(vm, src_type, BASE_DATA_GPA + slot_size * i,
BASE_DATA_SLOT + i, slot_size / vm->page_size,
- KVM_MEM_GUEST_MEMFD, memfd, slot_size * i);
+ KVM_MEM_GUEST_MEMFD, memfd, slot_size * i, 0);
for (i = 0; i < nr_vcpus; i++) {
uint64_t gpa = BASE_DATA_GPA + i * per_cpu_size;
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 14/43] KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Rename local variables and function parameters for the guest memory file
descriptor and its offset to use a "gmem_" prefix instead of
"guest_memfd_".
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/lib/kvm_util.c | 26 +++++++++++++-------------
1 file changed, 13 insertions(+), 13 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 610cb32ff207e..3b64fbadcd88d 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -947,7 +947,7 @@ void vm_set_user_memory_region(struct kvm_vm *vm, uint32_t slot, uint32_t flags,
int __vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flags,
uint64_t gpa, uint64_t size, void *hva,
- uint32_t guest_memfd, uint64_t guest_memfd_offset)
+ uint32_t gmem_fd, uint64_t gmem_offset)
{
struct kvm_userspace_memory_region2 region = {
.slot = slot,
@@ -955,8 +955,8 @@ int __vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flag
.guest_phys_addr = gpa,
.memory_size = size,
.userspace_addr = (uintptr_t)hva,
- .guest_memfd = guest_memfd,
- .guest_memfd_offset = guest_memfd_offset,
+ .guest_memfd = gmem_fd,
+ .guest_memfd_offset = gmem_offset,
};
TEST_REQUIRE_SET_USER_MEMORY_REGION2();
@@ -966,10 +966,10 @@ int __vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flag
void vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flags,
uint64_t gpa, uint64_t size, void *hva,
- uint32_t guest_memfd, uint64_t guest_memfd_offset)
+ uint32_t gmem_fd, uint64_t gmem_offset)
{
int ret = __vm_set_user_memory_region2(vm, slot, flags, gpa, size, hva,
- guest_memfd, guest_memfd_offset);
+ gmem_fd, gmem_offset);
TEST_ASSERT(!ret, "KVM_SET_USER_MEMORY_REGION2 failed, errno = %d (%s)",
errno, strerror(errno));
@@ -979,7 +979,7 @@ void vm_set_user_memory_region2(struct kvm_vm *vm, uint32_t slot, uint32_t flags
/* FIXME: This thing needs to be ripped apart and rewritten. */
void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
uint64_t gpa, uint32_t slot, uint64_t npages, uint32_t flags,
- int guest_memfd, uint64_t guest_memfd_offset)
+ int gmem_fd, uint64_t gmem_offset)
{
int ret;
struct userspace_mem_region *region;
@@ -1062,12 +1062,12 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
region->mmap_size += alignment;
if (flags & KVM_MEM_GUEST_MEMFD) {
- if (guest_memfd < 0) {
- uint32_t guest_memfd_flags = 0;
+ if (gmem_fd < 0) {
+ uint32_t gmem_flags = 0;
- TEST_ASSERT(!guest_memfd_offset,
+ TEST_ASSERT(!gmem_offset,
"Offset must be zero when creating new guest_memfd");
- guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
+ gmem_fd = vm_create_guest_memfd(vm, mem_size, gmem_flags);
} else {
/*
* Install a unique fd for each memslot so that the fd
@@ -1075,11 +1075,11 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
* needing to track if the fd is owned by the framework
* or by the caller.
*/
- guest_memfd = kvm_dup(guest_memfd);
+ gmem_fd = kvm_dup(gmem_fd);
}
- region->region.guest_memfd = guest_memfd;
- region->region.guest_memfd_offset = guest_memfd_offset;
+ region->region.guest_memfd = gmem_fd;
+ region->region.guest_memfd_offset = gmem_offset;
} else {
region->region.guest_memfd = -1;
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 13/43] KVM: selftests: Create gmem fd before "regular" fd when adding memslot
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
When adding a memslot associated a guest_memfd instance, create/dup the
guest_memfd before creating the "normal" backing file. This will allow
dup'ing the gmem fd as the normal fd when guest_memfd supports mmap(),
i.e. to make guest_memfd the _only_ backing source for the memslot.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
tools/testing/selftests/kvm/lib/kvm_util.c | 45 +++++++++++++++---------------
1 file changed, 23 insertions(+), 22 deletions(-)
diff --git a/tools/testing/selftests/kvm/lib/kvm_util.c b/tools/testing/selftests/kvm/lib/kvm_util.c
index 1959bf556e88e..610cb32ff207e 100644
--- a/tools/testing/selftests/kvm/lib/kvm_util.c
+++ b/tools/testing/selftests/kvm/lib/kvm_util.c
@@ -1061,6 +1061,29 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
if (alignment > 1)
region->mmap_size += alignment;
+ if (flags & KVM_MEM_GUEST_MEMFD) {
+ if (guest_memfd < 0) {
+ uint32_t guest_memfd_flags = 0;
+
+ TEST_ASSERT(!guest_memfd_offset,
+ "Offset must be zero when creating new guest_memfd");
+ guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
+ } else {
+ /*
+ * Install a unique fd for each memslot so that the fd
+ * can be closed when the region is deleted without
+ * needing to track if the fd is owned by the framework
+ * or by the caller.
+ */
+ guest_memfd = kvm_dup(guest_memfd);
+ }
+
+ region->region.guest_memfd = guest_memfd;
+ region->region.guest_memfd_offset = guest_memfd_offset;
+ } else {
+ region->region.guest_memfd = -1;
+ }
+
region->fd = -1;
if (backing_src_is_shared(src_type))
region->fd = kvm_memfd_alloc(region->mmap_size,
@@ -1090,28 +1113,6 @@ void vm_mem_add(struct kvm_vm *vm, enum vm_mem_backing_src_type src_type,
region->backing_src_type = src_type;
- if (flags & KVM_MEM_GUEST_MEMFD) {
- if (guest_memfd < 0) {
- uint32_t guest_memfd_flags = 0;
- TEST_ASSERT(!guest_memfd_offset,
- "Offset must be zero when creating new guest_memfd");
- guest_memfd = vm_create_guest_memfd(vm, mem_size, guest_memfd_flags);
- } else {
- /*
- * Install a unique fd for each memslot so that the fd
- * can be closed when the region is deleted without
- * needing to track if the fd is owned by the framework
- * or by the caller.
- */
- guest_memfd = kvm_dup(guest_memfd);
- }
-
- region->region.guest_memfd = guest_memfd;
- region->region.guest_memfd_offset = guest_memfd_offset;
- } else {
- region->region.guest_memfd = -1;
- }
-
region->unused_phy_pages = sparsebit_alloc();
if (vm_arch_has_protected_memory(vm))
region->protected_phy_pages = sparsebit_alloc();
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 12/43] KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Make vm_memory_attributes a module parameter so that userspace can disable
the use of memory attributes on the VM level.
To avoid inconsistencies in the way memory attributes are tracked in KVM
and guest_memfd, the vm_memory_attributes module_param is made
read-only (0444).
Make CONFIG_KVM_VM_MEMORY_ATTRIBUTES selectable, only for (CoCo) VM types
that might use vm_memory_attributes.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
arch/x86/kvm/Kconfig | 13 +++++++++----
virt/kvm/kvm_main.c | 1 +
2 files changed, 10 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index b6d65ee664d0f..8b97d341bd33f 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -82,13 +82,20 @@ config KVM_WERROR
config KVM_VM_MEMORY_ATTRIBUTES
select KVM_MEMORY_ATTRIBUTES
- bool
+ depends on KVM_SW_PROTECTED_VM || KVM_INTEL_TDX || KVM_AMD_SEV
+ bool "Enable per-VM memory attributes (for CoCo VMs)"
+ help
+ Enable support for per-VM memory attributes, which are deprecated in
+ favor of tracking memory attributes in guest_memfd. Select this if
+ you need to run CoCo VMs using a VMM that doesn't support guest_memfd
+ memory attributes.
+
+ If unsure, say N.
config KVM_SW_PROTECTED_VM
bool "Enable support for KVM software-protected VMs"
depends on EXPERT
depends on KVM_X86 && X86_64
- select KVM_VM_MEMORY_ATTRIBUTES
help
Enable support for KVM software-protected VMs. Currently, software-
protected VMs are purely a development and testing vehicle for
@@ -139,7 +146,6 @@ config KVM_INTEL_TDX
bool "Intel Trust Domain Extensions (TDX) support"
default y
depends on INTEL_TDX_HOST
- select KVM_VM_MEMORY_ATTRIBUTES
select HAVE_KVM_ARCH_GMEM_POPULATE
help
Provides support for launching Intel Trust Domain Extensions (TDX)
@@ -163,7 +169,6 @@ config KVM_AMD_SEV
depends on KVM_AMD && X86_64
depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
select ARCH_HAS_CC_PLATFORM
- select KVM_VM_MEMORY_ATTRIBUTES
select HAVE_KVM_ARCH_GMEM_PREPARE
select HAVE_KVM_ARCH_GMEM_INVALIDATE
select HAVE_KVM_ARCH_GMEM_POPULATE
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b8f5ce3a33e27..9744d3a7fd917 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -105,6 +105,7 @@ module_param(allow_unsafe_mappings, bool, 0444);
#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
bool vm_memory_attributes = true;
+module_param(vm_memory_attributes, bool, 0444);
#endif
DEFINE_STATIC_CALL_RET0(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
EXPORT_SYMBOL_FOR_KVM_INTERNAL(STATIC_CALL_KEY(__kvm_get_memory_attributes));
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 11/43] KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Bury KVM_VM_MEMORY_ATTRIBUTES in x86 to discourage other architectures
from adding support for per-VM memory attributes, because tracking private
vs. shared memory on a per-VM basis is now deprecated in favor of tracking
on a per-guest_memfd basis, and no other memory attributes are on the
horizon.
This will also allow modifying KVM_VM_MEMORY_ATTRIBUTES to be
user-selectable (in x86) without creating weirdness in KVM's Kconfigs.
Now that guest_memfd support memory attributes, it's entirely possible to
run x86 CoCo VMs without support for KVM_VM_MEMORY_ATTRIBUTES.
Leave the code itself in common KVM so that it's trivial to undo this
change if new per-VM attributes do come along.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/Kconfig | 4 ++++
virt/kvm/Kconfig | 4 ----
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 26f6afd51bbdc..b6d65ee664d0f 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -80,6 +80,10 @@ config KVM_WERROR
If in doubt, say "N".
+config KVM_VM_MEMORY_ATTRIBUTES
+ select KVM_MEMORY_ATTRIBUTES
+ bool
+
config KVM_SW_PROTECTED_VM
bool "Enable support for KVM software-protected VMs"
depends on EXPERT
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index e371e079e2c50..663de6421eda2 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -103,10 +103,6 @@ config KVM_MMU_LOCKLESS_AGING
config KVM_MEMORY_ATTRIBUTES
bool
-config KVM_VM_MEMORY_ATTRIBUTES
- select KVM_MEMORY_ATTRIBUTES
- bool
-
config KVM_GUEST_MEMFD
select XARRAY_MULTI
select KVM_MEMORY_ATTRIBUTES
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 10/43] KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
When checking if a guest_memfd folio is safe for conversion, its refcount
is examined. A folio may be present in a per-CPU lru_add fbatch, which
temporarily increases its refcount. This can lead to a false positive,
incorrectly indicating that the folio is in use and preventing the
conversion, even if it is otherwise safe. The conversion process might not
be on the same CPU that holds the folio in its fbatch, making a simple
per-CPU check insufficient.
To address this, drain all CPUs' lru_add fbatches if an unexpectedly high
refcount is encountered during the safety check. This is performed at most
once per conversion request.
guest_memfd folios are unevictable, so they can only reside in the lru_add
fbatch. If the folio's refcount is still unsafe after draining, then the
conversion is truly deemed unsafe.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
virt/kvm/guest_memfd.c | 22 ++++++++++++++++------
1 file changed, 16 insertions(+), 6 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 8e4866bb8145d..c4f6bdad6289e 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -8,6 +8,7 @@
#include <linux/mempolicy.h>
#include <linux/pseudo_fs.h>
#include <linux/pagemap.h>
+#include <linux/swap.h>
#include "kvm_mm.h"
@@ -566,25 +567,34 @@ static bool kvm_gmem_range_has_attributes(struct maple_tree *mt,
return true;
}
-static bool kvm_gmem_is_safe_for_conversion(struct inode *inode, pgoff_t start,
- size_t nr_pages, pgoff_t *err_index)
+static bool kvm_gmem_is_safe_for_conversion(struct inode *inode,
+ pgoff_t start, size_t nr_pages,
+ pgoff_t *err_index)
{
struct address_space *mapping = inode->i_mapping;
const int filemap_get_folios_refcount = 1;
pgoff_t last = start + nr_pages - 1;
struct folio_batch fbatch;
+ bool lru_drained = false;
bool safe = true;
int i;
folio_batch_init(&fbatch);
while (safe && filemap_get_folios(mapping, &start, last, &fbatch)) {
- for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+ for (i = 0; i < folio_batch_count(&fbatch);) {
struct folio *folio = fbatch.folios[i];
- if (folio_ref_count(folio) !=
- folio_nr_pages(folio) + filemap_get_folios_refcount) {
- safe = false;
+ safe = (folio_ref_count(folio) ==
+ folio_nr_pages(folio) +
+ filemap_get_folios_refcount);
+
+ if (safe) {
+ ++i;
+ } else if (!lru_drained) {
+ lru_add_drain_all();
+ lru_drained = true;
+ } else {
*err_index = folio->index;
break;
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 09/43] KVM: guest_memfd: Add support for KVM_SET_MEMORY_ATTRIBUTES2
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
For shared to private conversions, if refcounts on any of the folios
within the range are elevated, fail the conversion with -EAGAIN.
At the point of shared to private conversion, all folios in range are
also unmapped. The filemap_invalidate_lock() is held, so no faulting
can occur. Hence, from that point on, only transient refcounts can be
taken on the folios associated with that guest_memfd.
Hence, it is safe to do the conversion from shared to private.
After conversion is complete, refcounts may become elevated, but that
is fine since users of transient refcounts don't actually access
memory.
For private to shared conversions, there are no refcount checks, since
the guest is the only user of private pages, and guest_memfd will be the
only holder of refcounts on private pages.
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
Documentation/virt/kvm/api.rst | 48 +++++++++-
include/linux/kvm_host.h | 10 ++
include/uapi/linux/kvm.h | 9 +-
virt/kvm/Kconfig | 1 +
virt/kvm/guest_memfd.c | 211 ++++++++++++++++++++++++++++++++++++++---
virt/kvm/kvm_main.c | 15 +--
6 files changed, 264 insertions(+), 30 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 0b61e2579e1d8..15148c80cfdb6 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -117,7 +117,7 @@ description:
x86 includes both i386 and x86_64.
Type:
- system, vm, or vcpu.
+ system, vm, vcpu or guest_memfd.
Parameters:
what parameters are accepted by the ioctl.
@@ -6557,11 +6557,22 @@ KVM_S390_KEYOP_SSKE
---------------------------------
:Capability: KVM_CAP_MEMORY_ATTRIBUTES2
-:Architectures: x86
-:Type: vm ioctl
+:Architectures: all
+:Type: vm, guest_memfd ioctl
:Parameters: struct kvm_memory_attributes2 (in/out)
:Returns: 0 on success, <0 on error
+Errors:
+
+ ========== ===============================================================
+ EINVAL The specified `offset` or `size` were invalid (e.g. not
+ page aligned, causes an overflow, or size is zero).
+ EFAULT The parameter address was invalid.
+ EAGAIN Some page within requested range had unexpected refcounts. The
+ offset of the page will be returned in `error_offset`.
+ ENOMEM Ran out of memory trying to track private/shared state
+ ========== ===============================================================
+
KVM_SET_MEMORY_ATTRIBUTES2 is an extension to
KVM_SET_MEMORY_ATTRIBUTES that supports returning (writing) values to
userspace. The original (pre-extension) fields are shared with
@@ -6572,15 +6583,42 @@ Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
::
struct kvm_memory_attributes2 {
- __u64 address;
+ /* in */
+ union {
+ __u64 address;
+ __u64 offset;
+ };
__u64 size;
__u64 attributes;
__u64 flags;
- __u64 reserved[12];
+ /* out */
+ __u64 error_offset;
+ __u64 reserved[11];
};
#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
+Set attributes for a range of offsets within a guest_memfd to
+KVM_MEMORY_ATTRIBUTE_PRIVATE to limit the specified guest_memfd backed
+memory range for guest_use. Even if KVM_CAP_GUEST_MEMFD_MMAP is
+supported, after a successful call to set
+KVM_MEMORY_ATTRIBUTE_PRIVATE, the requested range will not be mappable
+into host userspace and will only be mappable by the guest.
+
+To allow the range to be mappable into host userspace again, call
+KVM_SET_MEMORY_ATTRIBUTES2 on the guest_memfd again with
+KVM_MEMORY_ATTRIBUTE_PRIVATE unset.
+
+If this ioctl returns -EAGAIN, the offset of the page with unexpected
+refcounts will be returned in `error_offset`. This can occur if there
+are transient refcounts on the pages, taken by other parts of the
+kernel.
+
+Userspace is expected to figure out how to remove all known refcounts
+on the shared pages, such as refcounts taken by get_user_pages(), and
+try the ioctl again. A possible source of these long term refcounts is
+if the guest_memfd memory was pinned in IOMMU page tables.
+
See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`.
.. _kvm_run:
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 19f026f8de390..1ea14c66fc82e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2514,6 +2514,16 @@ static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot)
}
#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
+static inline u64 kvm_supported_mem_attributes(struct kvm *kvm)
+{
+#ifdef kvm_arch_has_private_mem
+ if (!kvm || kvm_arch_has_private_mem(kvm))
+ return KVM_MEMORY_ATTRIBUTE_PRIVATE;
+#endif
+
+ return 0;
+}
+
typedef unsigned long (kvm_get_memory_attributes_t)(struct kvm *kvm, gfn_t gfn);
DECLARE_STATIC_CALL(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 16567d4a769e5..29baaa60de35a 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -990,6 +990,7 @@ struct kvm_enable_cap {
#define KVM_CAP_S390_USER_OPEREXEC 246
#define KVM_CAP_S390_KEYOP 247
#define KVM_CAP_MEMORY_ATTRIBUTES2 248
+#define KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES 249
struct kvm_irq_routing_irqchip {
__u32 irqchip;
@@ -1642,11 +1643,15 @@ struct kvm_memory_attributes {
#define KVM_SET_MEMORY_ATTRIBUTES2 _IOWR(KVMIO, 0xd2, struct kvm_memory_attributes2)
struct kvm_memory_attributes2 {
- __u64 address;
+ union {
+ __u64 address;
+ __u64 offset;
+ };
__u64 size;
__u64 attributes;
__u64 flags;
- __u64 reserved[12];
+ __u64 error_offset;
+ __u64 reserved[11];
};
#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 3fea89c45cfb4..e371e079e2c50 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -109,6 +109,7 @@ config KVM_VM_MEMORY_ATTRIBUTES
config KVM_GUEST_MEMFD
select XARRAY_MULTI
+ select KVM_MEMORY_ATTRIBUTES
bool
config HAVE_KVM_ARCH_GMEM_PREPARE
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 501f4d6e87909..8e4866bb8145d 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -178,10 +178,12 @@ static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index)
static enum kvm_gfn_range_filter kvm_gmem_get_invalidate_filter(struct inode *inode)
{
- if (GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED)
- return KVM_FILTER_SHARED;
-
- return KVM_FILTER_PRIVATE;
+ /*
+ * TODO: Limit invalidations based on the to-be-invalidated range, i.e.
+ * invalidate shared/private if and only if there can possibly be
+ * such mappings.
+ */
+ return KVM_FILTER_SHARED | KVM_FILTER_PRIVATE;
}
static void __kvm_gmem_invalidate_begin(struct gmem_file *f, pgoff_t start,
@@ -547,11 +549,201 @@ unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_memory_attributes);
+static bool kvm_gmem_range_has_attributes(struct maple_tree *mt,
+ pgoff_t index, size_t nr_pages,
+ u64 attributes)
+{
+ pgoff_t end = index + nr_pages - 1;
+ void *entry;
+
+ lockdep_assert(mt_lock_is_held(mt));
+
+ mt_for_each(mt, entry, index, end) {
+ if (xa_to_value(entry) != attributes)
+ return false;
+ }
+
+ return true;
+}
+
+static bool kvm_gmem_is_safe_for_conversion(struct inode *inode, pgoff_t start,
+ size_t nr_pages, pgoff_t *err_index)
+{
+ struct address_space *mapping = inode->i_mapping;
+ const int filemap_get_folios_refcount = 1;
+ pgoff_t last = start + nr_pages - 1;
+ struct folio_batch fbatch;
+ bool safe = true;
+ int i;
+
+ folio_batch_init(&fbatch);
+ while (safe && filemap_get_folios(mapping, &start, last, &fbatch)) {
+
+ for (i = 0; i < folio_batch_count(&fbatch); ++i) {
+ struct folio *folio = fbatch.folios[i];
+
+ if (folio_ref_count(folio) !=
+ folio_nr_pages(folio) + filemap_get_folios_refcount) {
+ safe = false;
+ *err_index = folio->index;
+ break;
+ }
+ }
+
+ folio_batch_release(&fbatch);
+ }
+
+ return safe;
+}
+
+/*
+ * Preallocate memory for attributes to be stored on a maple tree, pointed to
+ * by mas. Adjacent ranges with attributes identical to the new attributes
+ * will be merged. Also sets mas's bounds up for storing attributes.
+ *
+ * This maintains the invariant that ranges with the same attributes will
+ * always be merged.
+ */
+static int kvm_gmem_mas_preallocate(struct ma_state *mas, u64 attributes,
+ pgoff_t start, size_t nr_pages)
+{
+ pgoff_t end = start + nr_pages;
+ pgoff_t last = end - 1;
+ void *entry;
+
+ /* Try extending range. entry is NULL on overflow/wrap-around. */
+ mas_set_range(mas, end, end);
+ entry = mas_find(mas, end);
+ if (entry && xa_to_value(entry) == attributes)
+ last = mas->last;
+
+ if (start > 0) {
+ mas_set_range(mas, start - 1, start - 1);
+ entry = mas_find(mas, start - 1);
+ if (entry && xa_to_value(entry) == attributes)
+ start = mas->index;
+ }
+
+ mas_set_range(mas, start, last);
+ return mas_preallocate(mas, xa_mk_value(attributes), GFP_KERNEL);
+}
+
+static int __kvm_gmem_set_attributes(struct inode *inode, pgoff_t start,
+ size_t nr_pages, uint64_t attrs,
+ pgoff_t *err_index)
+{
+ struct address_space *mapping = inode->i_mapping;
+ struct gmem_inode *gi = GMEM_I(inode);
+ pgoff_t end = start + nr_pages;
+ struct maple_tree *mt;
+ struct ma_state mas;
+ int r;
+
+ mt = &gi->attributes;
+
+ filemap_invalidate_lock(mapping);
+
+ mas_init(&mas, mt, start);
+
+ if (kvm_gmem_range_has_attributes(mt, start, nr_pages, attrs)) {
+ r = 0;
+ goto out;
+ }
+
+ r = kvm_gmem_mas_preallocate(&mas, attrs, start, nr_pages);
+ if (r) {
+ *err_index = start;
+ goto out;
+ }
+
+ if (attrs & KVM_MEMORY_ATTRIBUTE_PRIVATE) {
+ unmap_mapping_pages(mapping, start, nr_pages, false);
+
+ if (!kvm_gmem_is_safe_for_conversion(inode, start, nr_pages,
+ err_index)) {
+ mas_destroy(&mas);
+ r = -EAGAIN;
+ goto out;
+ }
+ }
+
+ kvm_gmem_invalidate_begin(inode, start, end);
+
+ mas_store_prealloc(&mas, xa_mk_value(attrs));
+
+ kvm_gmem_invalidate_end(inode, start, end);
+out:
+ filemap_invalidate_unlock(mapping);
+ return r;
+}
+
+static long kvm_gmem_set_attributes(struct file *file, void __user *argp)
+{
+ struct gmem_file *f = file->private_data;
+ struct inode *inode = file_inode(file);
+ struct kvm_memory_attributes2 attrs;
+ pgoff_t err_index;
+ size_t nr_pages;
+ pgoff_t index;
+ int i, r;
+
+ if (copy_from_user(&attrs, argp, sizeof(attrs)))
+ return -EFAULT;
+
+ if (attrs.flags)
+ return -EINVAL;
+ if (attrs.error_offset)
+ return -EINVAL;
+ for (i = 0; i < ARRAY_SIZE(attrs.reserved); i++) {
+ if (attrs.reserved[i])
+ return -EINVAL;
+ }
+ if (attrs.attributes & ~kvm_supported_mem_attributes(f->kvm))
+ return -EINVAL;
+ if (attrs.size == 0 || attrs.offset + attrs.size < attrs.offset)
+ return -EINVAL;
+ if (!PAGE_ALIGNED(attrs.offset) || !PAGE_ALIGNED(attrs.size))
+ return -EINVAL;
+
+ if (attrs.offset >= inode->i_size ||
+ attrs.offset + attrs.size > inode->i_size)
+ return -EINVAL;
+
+ nr_pages = attrs.size >> PAGE_SHIFT;
+ index = attrs.offset >> PAGE_SHIFT;
+ r = __kvm_gmem_set_attributes(inode, index, nr_pages, attrs.attributes,
+ &err_index);
+ if (r) {
+ attrs.error_offset = err_index << PAGE_SHIFT;
+
+ if (copy_to_user(argp, &attrs, sizeof(attrs)))
+ return -EFAULT;
+ }
+
+ return r;
+}
+
+static long kvm_gmem_ioctl(struct file *file, unsigned int ioctl,
+ unsigned long arg)
+{
+ switch (ioctl) {
+ case KVM_SET_MEMORY_ATTRIBUTES2:
+ if (vm_memory_attributes)
+ return -ENOTTY;
+
+ return kvm_gmem_set_attributes(file, (void __user *)arg);
+ default:
+ return -ENOTTY;
+ }
+}
+
+
static struct file_operations kvm_gmem_fops = {
.mmap = kvm_gmem_mmap,
.open = generic_file_open,
.release = kvm_gmem_release,
.fallocate = kvm_gmem_fallocate,
+ .unlocked_ioctl = kvm_gmem_ioctl,
};
static int kvm_gmem_migrate_folio(struct address_space *mapping,
@@ -934,20 +1126,13 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
static bool kvm_gmem_range_is_private(struct gmem_inode *gi, pgoff_t index,
size_t nr_pages, struct kvm *kvm, gfn_t gfn)
{
- pgoff_t end = index + nr_pages - 1;
- void *entry;
-
if (vm_memory_attributes)
return kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + nr_pages,
KVM_MEMORY_ATTRIBUTE_PRIVATE,
KVM_MEMORY_ATTRIBUTE_PRIVATE);
- mt_for_each(&gi->attributes, entry, index, end) {
- if (xa_to_value(entry) != attributes)
- return false;
- }
-
- return true;
+ return kvm_gmem_range_has_attributes(&gi->attributes, index, nr_pages,
+ KVM_MEMORY_ATTRIBUTE_PRIVATE);
}
static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 89c31eb71a1ca..b8f5ce3a33e27 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2435,16 +2435,6 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
-static u64 kvm_supported_mem_attributes(struct kvm *kvm)
-{
-#ifdef kvm_arch_has_private_mem
- if (!kvm || kvm_arch_has_private_mem(kvm))
- return KVM_MEMORY_ATTRIBUTE_PRIVATE;
-#endif
-
- return 0;
-}
-
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static unsigned long kvm_get_vm_memory_attributes(struct kvm *kvm, gfn_t gfn)
{
@@ -4978,6 +4968,11 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
return 1;
case KVM_CAP_GUEST_MEMFD_FLAGS:
return kvm_gmem_get_supported_flags(kvm);
+ case KVM_CAP_GUEST_MEMFD_MEMORY_ATTRIBUTES:
+ if (vm_memory_attributes)
+ return 0;
+
+ return kvm_supported_mem_attributes(kvm);
#endif
default:
break;
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 08/43] KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Now that guest_memfd supports tracking private vs. shared within gmem
itself, allow userspace to specify INIT_SHARED on a guest_memfd instance
for x86 Confidential Computing (CoCo) VMs, so long as per-VM attributes
are disabled, i.e. when it's actually possible for a guest_memfd instance
to contain shared memory.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/kvm/x86.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 7e133a9da11f0..9c29407712580 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -14056,14 +14056,13 @@ bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
}
#ifdef CONFIG_KVM_GUEST_MEMFD
-/*
- * KVM doesn't yet support initializing guest_memfd memory as shared for VMs
- * with private memory (the private vs. shared tracking needs to be moved into
- * guest_memfd).
- */
bool kvm_arch_supports_gmem_init_shared(struct kvm *kvm)
{
- return !kvm_arch_has_private_mem(kvm);
+ /*
+ * INIT_SHARED isn't supported if the memory attributes are per-VM,
+ * in which case guest_memfd can _only_ be used for private memory.
+ */
+ return !vm_memory_attributes || !kvm_arch_has_private_mem(kvm);
}
#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_PREPARE
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 07/43] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Introduce a "version 2" of KVM_SET_MEMORY_ATTRIBUTES to support returning
information back to userspace.
This new ioctl and structure will, in a later patch, be shared as a
guest_memfd ioctl, where the padding in the new kvm_memory_attributes2
structure will be for writing the response from the guest_memfd ioctl to
userspace.
A new ioctl is necessary for these reasons:
1. KVM_SET_MEMORY_ATTRIBUTES is currently a write-only ioctl and does not
allow userspace to read fields. There's nothing in code (yet?) that
validates this, but using _IOWR for consistency would be prudent.
2. KVM_SET_MEMORY_ATTRIBUTES, when used as a guest_memfd ioctl, will need
an additional field to provide userspace with more error details.
Alternatively, a completely new ioctl could be defined, unrelated to
KVM_SET_MEMORY_ATTRIBUTES, but using the same ioctl number and struct for
the vm and guest_memfd ioctls streamlines the interface for userspace. In
addition, any memory attributes, implemented on the vm or guest_memfd
ioctl, can be easily shared with the other.
Add KVM_CAP_MEMORY_ATTRIBUTES2 to indicate that struct
kvm_memory_attributes2 exists and can be used either with
KVM_SET_MEMORY_ATTRIBUTES2 via the vm or guest_memfd ioctl.
Since KVM_SET_MEMORY_ATTRIBUTES2 is not limited to be used only with the vm
ioctl, return 1 for KVM_CAP_MEMORY_ATTRIBUTES2 as long as struct
kvm_memory_attributes2 and KVM_SET_MEMORY_ATTRIBUTES2 can be
used. KVM_CAP_MEMORY_ATTRIBUTES must still be used to actually get valid
attributes.
Handle KVM_CAP_MEMORY_ATTRIBUTES2 and return 1 regardless of
CONFIG_KVM_VM_MEMORY_ATTRIBUTES, since KVM_SET_MEMORY_ATTRIBUTES2 is not
limited to a vm ioctl and can also be used with the guest_memfd ioctl.
Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
Documentation/virt/kvm/api.rst | 32 ++++++++++++++++++++++++++++++++
include/uapi/linux/kvm.h | 12 ++++++++++++
virt/kvm/kvm_main.c | 35 ++++++++++++++++++++++++++++++++---
3 files changed, 76 insertions(+), 3 deletions(-)
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 032516783e962..0b61e2579e1d8 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -6359,6 +6359,8 @@ S390:
Returns -EINVAL if the VM has the KVM_VM_S390_UCONTROL flag set.
Returns -EINVAL if called on a protected VM.
+.. _KVM_SET_MEMORY_ATTRIBUTES:
+
4.141 KVM_SET_MEMORY_ATTRIBUTES
-------------------------------
@@ -6551,6 +6553,36 @@ KVM_S390_KEYOP_SSKE
Sets the storage key for the guest address ``guest_addr`` to the key
specified in ``key``, returning the previous value in ``key``.
+4.145 KVM_SET_MEMORY_ATTRIBUTES2
+---------------------------------
+
+:Capability: KVM_CAP_MEMORY_ATTRIBUTES2
+:Architectures: x86
+:Type: vm ioctl
+:Parameters: struct kvm_memory_attributes2 (in/out)
+:Returns: 0 on success, <0 on error
+
+KVM_SET_MEMORY_ATTRIBUTES2 is an extension to
+KVM_SET_MEMORY_ATTRIBUTES that supports returning (writing) values to
+userspace. The original (pre-extension) fields are shared with
+KVM_SET_MEMORY_ATTRIBUTES identically.
+
+Attribute values are shared with KVM_SET_MEMORY_ATTRIBUTES.
+
+::
+
+ struct kvm_memory_attributes2 {
+ __u64 address;
+ __u64 size;
+ __u64 attributes;
+ __u64 flags;
+ __u64 reserved[12];
+ };
+
+ #define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
+
+See also: :ref: `KVM_SET_MEMORY_ATTRIBUTES`.
+
.. _kvm_run:
5. The kvm_run structure
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 80364d4dbebb0..16567d4a769e5 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -989,6 +989,7 @@ struct kvm_enable_cap {
#define KVM_CAP_ARM_SEA_TO_USER 245
#define KVM_CAP_S390_USER_OPEREXEC 246
#define KVM_CAP_S390_KEYOP 247
+#define KVM_CAP_MEMORY_ATTRIBUTES2 248
struct kvm_irq_routing_irqchip {
__u32 irqchip;
@@ -1637,6 +1638,17 @@ struct kvm_memory_attributes {
__u64 flags;
};
+/* Available with KVM_CAP_MEMORY_ATTRIBUTES2 */
+#define KVM_SET_MEMORY_ATTRIBUTES2 _IOWR(KVMIO, 0xd2, struct kvm_memory_attributes2)
+
+struct kvm_memory_attributes2 {
+ __u64 address;
+ __u64 size;
+ __u64 attributes;
+ __u64 flags;
+ __u64 reserved[12];
+};
+
#define KVM_MEMORY_ATTRIBUTE_PRIVATE (1ULL << 3)
#define KVM_CREATE_GUEST_MEMFD _IOWR(KVMIO, 0xd4, struct kvm_create_guest_memfd)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 70b594dafc5cc..89c31eb71a1ca 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2621,7 +2621,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
return r;
}
static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
- struct kvm_memory_attributes *attrs)
+ struct kvm_memory_attributes2 *attrs)
{
gfn_t start, end;
@@ -4966,6 +4966,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
case KVM_CAP_DEVICE_CTRL:
return 1;
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+ case KVM_CAP_MEMORY_ATTRIBUTES2:
case KVM_CAP_MEMORY_ATTRIBUTES:
if (!vm_memory_attributes)
return 0;
@@ -5191,6 +5192,14 @@ do { \
sizeof_field(struct kvm_userspace_memory_region2, field)); \
} while (0)
+#define SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(field) \
+do { \
+ BUILD_BUG_ON(offsetof(struct kvm_memory_attributes, field) != \
+ offsetof(struct kvm_memory_attributes2, field)); \
+ BUILD_BUG_ON(sizeof_field(struct kvm_memory_attributes, field) != \
+ sizeof_field(struct kvm_memory_attributes2, field)); \
+} while (0)
+
static long kvm_vm_ioctl(struct file *filp,
unsigned int ioctl, unsigned long arg)
{
@@ -5373,15 +5382,35 @@ static long kvm_vm_ioctl(struct file *filp,
}
#endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+ case KVM_SET_MEMORY_ATTRIBUTES2:
case KVM_SET_MEMORY_ATTRIBUTES: {
- struct kvm_memory_attributes attrs;
+ struct kvm_memory_attributes2 attrs;
+ unsigned long size;
+
+ if (ioctl == KVM_SET_MEMORY_ATTRIBUTES) {
+ /*
+ * Fields beyond struct kvm_memory_attributes shouldn't
+ * be accessed, but avoid leaking kernel memory in case
+ * of a bug.
+ */
+ memset(&attrs, 0, sizeof(attrs));
+ size = sizeof(struct kvm_memory_attributes);
+ } else {
+ size = sizeof(struct kvm_memory_attributes2);
+ }
+
+ /* Ensure the common parts of the two structs are identical. */
+ SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(address);
+ SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(size);
+ SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(attributes);
+ SANITY_CHECK_MEMORY_ATTRIBUTES_FIELD(flags);
r = -ENOTTY;
if (!vm_memory_attributes)
goto out;
r = -EFAULT;
- if (copy_from_user(&attrs, argp, sizeof(attrs)))
+ if (copy_from_user(&attrs, argp, size))
goto out;
r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs);
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 06/43] KVM: guest_memfd: Update kvm_gmem_populate() to use gmem attributes
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
Update the guest_memfd populate() flow to pull memory attributes from the
gmem instance instead of the VM when KVM is not configured to track
shared/private status in the VM.
Rename the per-VM API to make it clear that it retrieves per-VM
attributes, i.e. is not suitable for use outside of flows that are
specific to generic per-VM attributes.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
arch/x86/kvm/mmu/mmu.c | 2 +-
include/linux/kvm_host.h | 14 +++++++++++++-
virt/kvm/guest_memfd.c | 24 +++++++++++++++++++++---
virt/kvm/kvm_main.c | 8 +++-----
4 files changed, 38 insertions(+), 10 deletions(-)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 792701b093234..f21e16f22dd7b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7978,7 +7978,7 @@ static bool hugepage_has_attrs(struct kvm *kvm, struct kvm_memory_slot *slot,
const unsigned long end = start + KVM_PAGES_PER_HPAGE(level);
if (level == PG_LEVEL_2M)
- return kvm_range_has_memory_attributes(kvm, start, end, ~0, attrs);
+ return kvm_range_has_vm_memory_attributes(kvm, start, end, ~0, attrs);
for (gfn = start; gfn < end; gfn += KVM_PAGES_PER_HPAGE(level - 1)) {
if (hugepage_test_mixed(slot, gfn, level - 1) ||
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 0f84421b3f49e..19f026f8de390 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2534,12 +2534,24 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
#endif
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
-bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+extern bool vm_memory_attributes;
+bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
unsigned long mask, unsigned long attrs);
bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
+#else
+#define vm_memory_attributes false
+static inline bool kvm_range_has_vm_memory_attributes(struct kvm *kvm,
+ gfn_t start, gfn_t end,
+ unsigned long mask,
+ unsigned long attrs)
+{
+ WARN_ONCE(1, "Unexpected call to kvm_range_has_vm_memory_attributes()");
+
+ return false;
+}
#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn);
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index e93e95940ec74..501f4d6e87909 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -931,12 +931,31 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
#ifdef CONFIG_HAVE_KVM_ARCH_GMEM_POPULATE
+static bool kvm_gmem_range_is_private(struct gmem_inode *gi, pgoff_t index,
+ size_t nr_pages, struct kvm *kvm, gfn_t gfn)
+{
+ pgoff_t end = index + nr_pages - 1;
+ void *entry;
+
+ if (vm_memory_attributes)
+ return kvm_range_has_vm_memory_attributes(kvm, gfn, gfn + nr_pages,
+ KVM_MEMORY_ATTRIBUTE_PRIVATE,
+ KVM_MEMORY_ATTRIBUTE_PRIVATE);
+
+ mt_for_each(&gi->attributes, entry, index, end) {
+ if (xa_to_value(entry) != attributes)
+ return false;
+ }
+
+ return true;
+}
static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
struct file *file, gfn_t gfn, struct page *src_page,
kvm_gmem_populate_cb post_populate, void *opaque)
{
pgoff_t index = kvm_gmem_get_index(slot, gfn);
+ struct gmem_inode *gi;
struct folio *folio;
kvm_pfn_t pfn;
int ret;
@@ -951,9 +970,8 @@ static long __kvm_gmem_populate(struct kvm *kvm, struct kvm_memory_slot *slot,
folio_unlock(folio);
- if (!kvm_range_has_memory_attributes(kvm, gfn, gfn + 1,
- KVM_MEMORY_ATTRIBUTE_PRIVATE,
- KVM_MEMORY_ATTRIBUTE_PRIVATE)) {
+ gi = GMEM_I(file_inode(file));
+ if (!kvm_gmem_range_is_private(gi, index, 1, kvm, gfn)) {
ret = -EINVAL;
goto out_put_folio;
}
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 7bb59679c9316..70b594dafc5cc 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -104,9 +104,7 @@ module_param(allow_unsafe_mappings, bool, 0444);
#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
-static bool vm_memory_attributes = true;
-#else
-#define vm_memory_attributes false
+bool vm_memory_attributes = true;
#endif
DEFINE_STATIC_CALL_RET0(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
EXPORT_SYMBOL_FOR_KVM_INTERNAL(STATIC_CALL_KEY(__kvm_get_memory_attributes));
@@ -2457,7 +2455,7 @@ static unsigned long kvm_get_vm_memory_attributes(struct kvm *kvm, gfn_t gfn)
* Returns true if _all_ gfns in the range [@start, @end) have attributes
* such that the bits in @mask match @attrs.
*/
-bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+bool kvm_range_has_vm_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
unsigned long mask, unsigned long attrs)
{
XA_STATE(xas, &kvm->mem_attr_array, start);
@@ -2591,7 +2589,7 @@ static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
mutex_lock(&kvm->slots_lock);
/* Nothing to do if the entire range has the desired attributes. */
- if (kvm_range_has_memory_attributes(kvm, start, end, ~0, attributes))
+ if (kvm_range_has_vm_memory_attributes(kvm, start, end, ~0, attributes))
goto out_unlock;
/*
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 05/43] KVM: guest_memfd: Wire up kvm_get_memory_attributes() to per-gmem attributes
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Implement kvm_gmem_get_memory_attributes() for guest_memfd to allow the KVM
core and architecture code to query per-GFN memory attributes.
kvm_gmem_get_memory_attributes() finds the memory slot for a given GFN and
queries the guest_memfd file's to determine if the page is marked as
private.
If vm_memory_attributes is not enabled, there is no shared/private tracking
at the VM level. Install the guest_memfd implementation as long as
guest_memfd is enabled to give guest_memfd a chance to respond on
attributes.
guest_memfd should look up attributes regardless of whether this memslot is
gmem-only since attributes are now tracked by gmem regardless of whether
mmap() is enabled.
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
include/linux/kvm_host.h | 2 ++
virt/kvm/guest_memfd.c | 37 +++++++++++++++++++++++++++++++++++++
virt/kvm/kvm_main.c | 3 +++
3 files changed, 42 insertions(+)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 5393854ca5966..0f84421b3f49e 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2542,6 +2542,8 @@ bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
struct kvm_gfn_range *range);
#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn);
+
#ifdef CONFIG_KVM_GUEST_MEMFD
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
gfn_t gfn, kvm_pfn_t *pfn, struct page **page,
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 67709af03f39d..e93e95940ec74 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -510,6 +510,43 @@ static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vma)
return 0;
}
+unsigned long kvm_gmem_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
+{
+ struct kvm_memory_slot *slot = gfn_to_memslot(kvm, gfn);
+ struct inode *inode;
+ unsigned long attrs;
+
+ /*
+ * If this gfn has no associated memslot, there's no chance of the gfn
+ * being backed by private memory, since guest_memfd must be used for
+ * private memory, and guest_memfd must be associated with some memslot.
+ */
+ if (!slot)
+ return 0;
+
+ CLASS(gmem_get_file, file)(slot);
+ if (!file)
+ return 0;
+
+ inode = file_inode(file);
+
+ /*
+ * Acquire the filemap lock to ensure the mtree lookup gets a
+ * stable result. The caller _must_ still protect consumption
+ * of private vs. shared by checking
+ * mmu_invalidate_retry_gfn() under mmu_lock to serialize
+ * against ongoing attribute updates. Acquiring the filemap
+ * lock only ensures a stable _lookup_, the result can become
+ * stale as soon as the lock is dropped.
+ */
+ filemap_invalidate_lock_shared(inode->i_mapping);
+ attrs = kvm_gmem_get_attributes(inode, kvm_gmem_get_index(slot, gfn));
+ filemap_invalidate_unlock_shared(inode->i_mapping);
+
+ return attrs;
+}
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_memory_attributes);
+
static struct file_operations kvm_gmem_fops = {
.mmap = kvm_gmem_mmap,
.open = generic_file_open,
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index dbdcef90a4950..7bb59679c9316 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2660,6 +2660,9 @@ static void kvm_init_memory_attributes(void)
if (vm_memory_attributes)
static_call_update(__kvm_get_memory_attributes,
kvm_get_vm_memory_attributes);
+ else if (IS_ENABLED(CONFIG_KVM_GUEST_MEMFD))
+ static_call_update(__kvm_get_memory_attributes,
+ kvm_gmem_get_memory_attributes);
else
static_call_update(__kvm_get_memory_attributes,
(void *)__static_call_return0);
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 04/43] KVM: Stub in ability to disable per-VM memory attribute tracking
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Introduce the basic infrastructure to allow per-VM memory attribute
tracking to be disabled. This will be built-upon in a later patch, where a
module param can disable per-VM memory attribute tracking.
Split the Kconfig option into a base KVM_MEMORY_ATTRIBUTES and the
existing KVM_VM_MEMORY_ATTRIBUTES. The base option provides the core
plumbing, while the latter enables the full per-VM tracking via an xarray
and the associated ioctls.
kvm_get_memory_attributes() now performs a static call that either looks up
kvm->mem_attr_array with CONFIG_KVM_VM_MEMORY_ATTRIBUTES is enabled, or
just returns 0 otherwise. The static call can be patched depending on
whether per-VM tracking is enabled by the CONFIG.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
include/linux/kvm_host.h | 23 ++++++++++++---------
virt/kvm/Kconfig | 4 ++++
virt/kvm/kvm_main.c | 44 ++++++++++++++++++++++++++++++++++++++++-
4 files changed, 62 insertions(+), 11 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index cf3d2bdababc7..537f25121e345 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2329,7 +2329,7 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
int tdp_max_root_level, int tdp_huge_page_level);
-#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
#endif
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 4ba42a1278d5f..5393854ca5966 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -2513,19 +2513,15 @@ static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot)
return slot->flags & KVM_MEMSLOT_GMEM_ONLY;
}
-#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
+typedef unsigned long (kvm_get_memory_attributes_t)(struct kvm *kvm, gfn_t gfn);
+DECLARE_STATIC_CALL(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
+
static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
{
- return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
+ return static_call(__kvm_get_memory_attributes)(kvm, gfn);
}
-bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
- unsigned long mask, unsigned long attrs);
-bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
- struct kvm_gfn_range *range);
-bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
- struct kvm_gfn_range *range);
-
static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return kvm_get_memory_attributes(kvm, gfn) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
@@ -2535,6 +2531,15 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return false;
}
+#endif
+
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end,
+ unsigned long mask, unsigned long attrs);
+bool kvm_arch_pre_set_memory_attributes(struct kvm *kvm,
+ struct kvm_gfn_range *range);
+bool kvm_arch_post_set_memory_attributes(struct kvm *kvm,
+ struct kvm_gfn_range *range);
#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
#ifdef CONFIG_KVM_GUEST_MEMFD
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 5119cb37145fc..3fea89c45cfb4 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -100,7 +100,11 @@ config KVM_ELIDE_TLB_FLUSH_IF_YOUNG
config KVM_MMU_LOCKLESS_AGING
bool
+config KVM_MEMORY_ATTRIBUTES
+ bool
+
config KVM_VM_MEMORY_ATTRIBUTES
+ select KVM_MEMORY_ATTRIBUTES
bool
config KVM_GUEST_MEMFD
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 793a2c8476b09..dbdcef90a4950 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -102,6 +102,17 @@ EXPORT_SYMBOL_FOR_KVM_INTERNAL(halt_poll_ns_shrink);
static bool allow_unsafe_mappings;
module_param(allow_unsafe_mappings, bool, 0444);
+#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+static bool vm_memory_attributes = true;
+#else
+#define vm_memory_attributes false
+#endif
+DEFINE_STATIC_CALL_RET0(__kvm_get_memory_attributes, kvm_get_memory_attributes_t);
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(STATIC_CALL_KEY(__kvm_get_memory_attributes));
+EXPORT_SYMBOL_FOR_KVM_INTERNAL(STATIC_CALL_TRAMP(__kvm_get_memory_attributes));
+#endif
+
/*
* Ordering of locks:
*
@@ -2425,7 +2436,7 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
}
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
-#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_MEMORY_ATTRIBUTES
static u64 kvm_supported_mem_attributes(struct kvm *kvm)
{
#ifdef kvm_arch_has_private_mem
@@ -2436,6 +2447,12 @@ static u64 kvm_supported_mem_attributes(struct kvm *kvm)
return 0;
}
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+static unsigned long kvm_get_vm_memory_attributes(struct kvm *kvm, gfn_t gfn)
+{
+ return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
+}
+
/*
* Returns true if _all_ gfns in the range [@start, @end) have attributes
* such that the bits in @mask match @attrs.
@@ -2632,7 +2649,24 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
return kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
}
+#else /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+static unsigned long kvm_get_vm_memory_attributes(struct kvm *kvm, gfn_t gfn)
+{
+ BUILD_BUG_ON(1);
+}
#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
+static void kvm_init_memory_attributes(void)
+{
+ if (vm_memory_attributes)
+ static_call_update(__kvm_get_memory_attributes,
+ kvm_get_vm_memory_attributes);
+ else
+ static_call_update(__kvm_get_memory_attributes,
+ (void *)__static_call_return0);
+}
+#else /* CONFIG_KVM_MEMORY_ATTRIBUTES */
+static void kvm_init_memory_attributes(void) { }
+#endif /* CONFIG_KVM_MEMORY_ATTRIBUTES */
struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
{
@@ -4932,6 +4966,9 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
return 1;
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
case KVM_CAP_MEMORY_ATTRIBUTES:
+ if (!vm_memory_attributes)
+ return 0;
+
return kvm_supported_mem_attributes(kvm);
#endif
#ifdef CONFIG_KVM_GUEST_MEMFD
@@ -5338,6 +5375,10 @@ static long kvm_vm_ioctl(struct file *filp,
case KVM_SET_MEMORY_ATTRIBUTES: {
struct kvm_memory_attributes attrs;
+ r = -ENOTTY;
+ if (!vm_memory_attributes)
+ goto out;
+
r = -EFAULT;
if (copy_from_user(&attrs, argp, sizeof(attrs)))
goto out;
@@ -6528,6 +6569,7 @@ int kvm_init(unsigned vcpu_size, unsigned vcpu_align, struct module *module)
kvm_preempt_ops.sched_in = kvm_sched_in;
kvm_preempt_ops.sched_out = kvm_sched_out;
+ kvm_init_memory_attributes();
kvm_init_debug();
r = kvm_vfio_ops_init();
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 03/43] KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Explicitly guard reporting support for KVM_MEMORY_ATTRIBUTE_PRIVATE based
on kvm_arch_has_private_mem being #defined in anticipation of decoupling
kvm_supported_mem_attributes() from CONFIG_KVM_VM_MEMORY_ATTRIBUTES.
guest_memfd support for memory attributes will be unconditional to avoid
yet more macros (all architectures that support guest_memfd are expected to
use per-gmem attributes at some point), at which point enumerating support
KVM_MEMORY_ATTRIBUTE_PRIVATE based solely on memory attributes being
supported _somewhere_ would result in KVM over-reporting support on arm64.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
include/linux/kvm_host.h | 2 +-
virt/kvm/kvm_main.c | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index e75f7295af5d0..4ba42a1278d5f 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -721,7 +721,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
}
#endif
-#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
+#ifndef kvm_arch_has_private_mem
static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
{
return false;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 301d7ddac6ba6..793a2c8476b09 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2428,8 +2428,10 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static u64 kvm_supported_mem_attributes(struct kvm *kvm)
{
+#ifdef kvm_arch_has_private_mem
if (!kvm || kvm_arch_has_private_mem(kvm))
return KVM_MEMORY_ATTRIBUTE_PRIVATE;
+#endif
return 0;
}
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 02/43] KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Rename the per-VM memory attributes Kconfig to make it explicitly about
per-VM attributes in anticipation of adding memory attributes support to
guest_memfd, at which point it will be possible (and desirable) to have
memory attributes without the per-VM support, even in x86.
No functional change intended.
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/Kconfig | 6 +++---
arch/x86/kvm/mmu/mmu.c | 2 +-
arch/x86/kvm/x86.c | 2 +-
include/linux/kvm_host.h | 8 ++++----
include/trace/events/kvm.h | 4 ++--
virt/kvm/Kconfig | 2 +-
virt/kvm/kvm_main.c | 14 +++++++-------
8 files changed, 20 insertions(+), 20 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 6e4e3ef9b8c72..cf3d2bdababc7 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -2329,7 +2329,7 @@ void kvm_configure_mmu(bool enable_tdp, int tdp_forced_root_level,
int tdp_max_root_level, int tdp_huge_page_level);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
#define kvm_arch_has_private_mem(kvm) ((kvm)->arch.has_private_mem)
#endif
diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index 801bf9e520db3..26f6afd51bbdc 100644
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -84,7 +84,7 @@ config KVM_SW_PROTECTED_VM
bool "Enable support for KVM software-protected VMs"
depends on EXPERT
depends on KVM_X86 && X86_64
- select KVM_GENERIC_MEMORY_ATTRIBUTES
+ select KVM_VM_MEMORY_ATTRIBUTES
help
Enable support for KVM software-protected VMs. Currently, software-
protected VMs are purely a development and testing vehicle for
@@ -135,7 +135,7 @@ config KVM_INTEL_TDX
bool "Intel Trust Domain Extensions (TDX) support"
default y
depends on INTEL_TDX_HOST
- select KVM_GENERIC_MEMORY_ATTRIBUTES
+ select KVM_VM_MEMORY_ATTRIBUTES
select HAVE_KVM_ARCH_GMEM_POPULATE
help
Provides support for launching Intel Trust Domain Extensions (TDX)
@@ -159,7 +159,7 @@ config KVM_AMD_SEV
depends on KVM_AMD && X86_64
depends on CRYPTO_DEV_SP_PSP && !(KVM_AMD=y && CRYPTO_DEV_CCP_DD=m)
select ARCH_HAS_CC_PLATFORM
- select KVM_GENERIC_MEMORY_ATTRIBUTES
+ select KVM_VM_MEMORY_ATTRIBUTES
select HAVE_KVM_ARCH_GMEM_PREPARE
select HAVE_KVM_ARCH_GMEM_INVALIDATE
select HAVE_KVM_ARCH_GMEM_POPULATE
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index b922a8b000577..792701b093234 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -7889,7 +7889,7 @@ void kvm_mmu_pre_destroy_vm(struct kvm *kvm)
vhost_task_stop(kvm->arch.nx_huge_page_recovery_thread);
}
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static bool hugepage_test_mixed(struct kvm_memory_slot *slot, gfn_t gfn,
int level)
{
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index fd1c4a36b5936..7e133a9da11f0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13509,7 +13509,7 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm,
}
}
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
kvm_mmu_init_memslot_memory_attributes(kvm, slot);
#endif
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 6b76e7a6f4c22..e75f7295af5d0 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -721,7 +721,7 @@ static inline int kvm_arch_vcpu_memslots_id(struct kvm_vcpu *vcpu)
}
#endif
-#ifndef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifndef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static inline bool kvm_arch_has_private_mem(struct kvm *kvm)
{
return false;
@@ -870,7 +870,7 @@ struct kvm {
#ifdef CONFIG_HAVE_KVM_PM_NOTIFIER
struct notifier_block pm_notifier;
#endif
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
/* Protected by slots_lock (for writes) and RCU (for reads) */
struct xarray mem_attr_array;
#endif
@@ -2513,7 +2513,7 @@ static inline bool kvm_memslot_is_gmem_only(const struct kvm_memory_slot *slot)
return slot->flags & KVM_MEMSLOT_GMEM_ONLY;
}
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static inline unsigned long kvm_get_memory_attributes(struct kvm *kvm, gfn_t gfn)
{
return xa_to_value(xa_load(&kvm->mem_attr_array, gfn));
@@ -2535,7 +2535,7 @@ static inline bool kvm_mem_is_private(struct kvm *kvm, gfn_t gfn)
{
return false;
}
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
#ifdef CONFIG_KVM_GUEST_MEMFD
int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
diff --git a/include/trace/events/kvm.h b/include/trace/events/kvm.h
index b282e3a867696..1ba72bd73ea2f 100644
--- a/include/trace/events/kvm.h
+++ b/include/trace/events/kvm.h
@@ -358,7 +358,7 @@ TRACE_EVENT(kvm_dirty_ring_exit,
TP_printk("vcpu %d", __entry->vcpu_id)
);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
/*
* @start: Starting address of guest memory range
* @end: End address of guest memory range
@@ -383,7 +383,7 @@ TRACE_EVENT(kvm_vm_set_mem_attributes,
TP_printk("%#016llx -- %#016llx [0x%lx]",
__entry->start, __entry->end, __entry->attr)
);
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
TRACE_EVENT(kvm_unmap_hva_range,
TP_PROTO(unsigned long start, unsigned long end),
diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig
index 794976b88c6f9..5119cb37145fc 100644
--- a/virt/kvm/Kconfig
+++ b/virt/kvm/Kconfig
@@ -100,7 +100,7 @@ config KVM_ELIDE_TLB_FLUSH_IF_YOUNG
config KVM_MMU_LOCKLESS_AGING
bool
-config KVM_GENERIC_MEMORY_ATTRIBUTES
+config KVM_VM_MEMORY_ATTRIBUTES
bool
config KVM_GUEST_MEMFD
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9093251beb398..301d7ddac6ba6 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1122,7 +1122,7 @@ static struct kvm *kvm_create_vm(unsigned long type, const char *fdname)
spin_lock_init(&kvm->mn_invalidate_lock);
rcuwait_init(&kvm->mn_memslots_update_rcuwait);
xa_init(&kvm->vcpu_array);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
xa_init(&kvm->mem_attr_array);
#endif
@@ -1307,7 +1307,7 @@ static void kvm_destroy_vm(struct kvm *kvm)
cleanup_srcu_struct(&kvm->irq_srcu);
srcu_barrier(&kvm->srcu);
cleanup_srcu_struct(&kvm->srcu);
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
xa_destroy(&kvm->mem_attr_array);
#endif
kvm_arch_free_vm(kvm);
@@ -2425,7 +2425,7 @@ static int kvm_vm_ioctl_clear_dirty_log(struct kvm *kvm,
}
#endif /* CONFIG_KVM_GENERIC_DIRTYLOG_READ_PROTECT */
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
static u64 kvm_supported_mem_attributes(struct kvm *kvm)
{
if (!kvm || kvm_arch_has_private_mem(kvm))
@@ -2630,7 +2630,7 @@ static int kvm_vm_ioctl_set_mem_attributes(struct kvm *kvm,
return kvm_vm_set_mem_attributes(kvm, start, end, attrs->attributes);
}
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn)
{
@@ -4928,7 +4928,7 @@ static int kvm_vm_ioctl_check_extension_generic(struct kvm *kvm, long arg)
case KVM_CAP_SYSTEM_EVENT_DATA:
case KVM_CAP_DEVICE_CTRL:
return 1;
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
case KVM_CAP_MEMORY_ATTRIBUTES:
return kvm_supported_mem_attributes(kvm);
#endif
@@ -5332,7 +5332,7 @@ static long kvm_vm_ioctl(struct file *filp,
break;
}
#endif /* CONFIG_HAVE_KVM_IRQ_ROUTING */
-#ifdef CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES
+#ifdef CONFIG_KVM_VM_MEMORY_ATTRIBUTES
case KVM_SET_MEMORY_ATTRIBUTES: {
struct kvm_memory_attributes attrs;
@@ -5343,7 +5343,7 @@ static long kvm_vm_ioctl(struct file *filp,
r = kvm_vm_ioctl_set_mem_attributes(kvm, &attrs);
break;
}
-#endif /* CONFIG_KVM_GENERIC_MEMORY_ATTRIBUTES */
+#endif /* CONFIG_KVM_VM_MEMORY_ATTRIBUTES */
case KVM_CREATE_DEVICE: {
struct kvm_create_device cd;
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 01/43] KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
In-Reply-To: <20260313-gmem-inplace-conversion-v3-0-5fc12a70ec89@google.com>
From: Sean Christopherson <seanjc@google.com>
Start plumbing in guest_memfd support for in-place private<=>shared
conversions by tracking attributes via a maple tree. KVM currently tracks
private vs. shared attributes on a per-VM basis, which made sense when a
guest_memfd _only_ supported private memory, but tracking per-VM simply
can't work for in-place conversions as the shareability of a given page
needs to be per-gmem_inode, not per-VM.
Use the filemap invalidation lock to protect the maple tree, as taking the
lock for read when faulting in memory (for userspace or the guest) isn't
expected to result in meaningful contention, and using a separate lock
would add significant complexity (avoid deadlock is quite difficult).
Signed-off-by: Sean Christopherson <seanjc@google.com>
Co-developed-by: Ackerley Tng <ackerleytng@google.com>
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
Co-developed-by: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Vishal Annapurve <vannapurve@google.com>
Co-developed-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Fuad Tabba <tabba@google.com>
---
virt/kvm/guest_memfd.c | 134 +++++++++++++++++++++++++++++++++++++++++++------
1 file changed, 118 insertions(+), 16 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 017d84a7adf37..67709af03f39d 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -4,6 +4,7 @@
#include <linux/falloc.h>
#include <linux/fs.h>
#include <linux/kvm_host.h>
+#include <linux/maple_tree.h>
#include <linux/mempolicy.h>
#include <linux/pseudo_fs.h>
#include <linux/pagemap.h>
@@ -32,6 +33,7 @@ struct gmem_inode {
struct inode vfs_inode;
u64 flags;
+ struct maple_tree attributes;
};
static __always_inline struct gmem_inode *GMEM_I(struct inode *inode)
@@ -59,6 +61,31 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn)
return gfn - slot->base_gfn + slot->gmem.pgoff;
}
+static u64 kvm_gmem_get_attributes(struct inode *inode, pgoff_t index)
+{
+ struct maple_tree *mt = &GMEM_I(inode)->attributes;
+ void *entry = mtree_load(mt, index);
+
+ /*
+ * The lock _must_ be held for lookups, as some maple tree operations,
+ * e.g. append, are unsafe (return inaccurate information) with respect
+ * to concurrent RCU-protected lookups.
+ */
+ lockdep_assert(mt_lock_is_held(mt));
+
+ return WARN_ON_ONCE(!entry) ? 0 : xa_to_value(entry);
+}
+
+static bool kvm_gmem_is_private_mem(struct inode *inode, pgoff_t index)
+{
+ return kvm_gmem_get_attributes(inode, index) & KVM_MEMORY_ATTRIBUTE_PRIVATE;
+}
+
+static bool kvm_gmem_is_shared_mem(struct inode *inode, pgoff_t index)
+{
+ return !kvm_gmem_is_private_mem(inode, index);
+}
+
static int __kvm_gmem_prepare_folio(struct kvm *kvm, struct kvm_memory_slot *slot,
pgoff_t index, struct folio *folio)
{
@@ -397,10 +424,13 @@ static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf)
if (((loff_t)vmf->pgoff << PAGE_SHIFT) >= i_size_read(inode))
return VM_FAULT_SIGBUS;
- if (!(GMEM_I(inode)->flags & GUEST_MEMFD_FLAG_INIT_SHARED))
- return VM_FAULT_SIGBUS;
+ filemap_invalidate_lock_shared(inode->i_mapping);
+ if (kvm_gmem_is_shared_mem(inode, vmf->pgoff))
+ folio = kvm_gmem_get_folio(inode, vmf->pgoff);
+ else
+ folio = ERR_PTR(-EACCES);
+ filemap_invalidate_unlock_shared(inode->i_mapping);
- folio = kvm_gmem_get_folio(inode, vmf->pgoff);
if (IS_ERR(folio)) {
if (PTR_ERR(folio) == -EAGAIN)
return VM_FAULT_RETRY;
@@ -556,6 +586,51 @@ bool __weak kvm_arch_supports_gmem_init_shared(struct kvm *kvm)
return true;
}
+static int kvm_gmem_init_inode(struct inode *inode, loff_t size, u64 flags)
+{
+ struct gmem_inode *gi = GMEM_I(inode);
+ MA_STATE(mas, &gi->attributes, 0, (size >> PAGE_SHIFT) - 1);
+ u64 attrs;
+ int r;
+
+ inode->i_op = &kvm_gmem_iops;
+ inode->i_mapping->a_ops = &kvm_gmem_aops;
+ inode->i_mode |= S_IFREG;
+ inode->i_size = size;
+ mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
+
+ /*
+ * guest_memfd memory is neither migratable nor swappable: set
+ * inaccessible to gate off both.
+ */
+ mapping_set_inaccessible(inode->i_mapping);
+ WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
+
+ gi->flags = flags;
+
+ mt_set_external_lock(&gi->attributes,
+ &inode->i_mapping->invalidate_lock);
+
+ /*
+ * Store default attributes for the entire gmem instance. Ensuring every
+ * index is represented in the maple tree at all times simplifies the
+ * conversion and merging logic.
+ */
+ attrs = gi->flags & GUEST_MEMFD_FLAG_INIT_SHARED ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE;
+
+ /*
+ * Acquire the invalidation lock purely to make lockdep happy. The
+ * maple tree library expects all stores to be protected via the lock,
+ * and the library can't know when the tree is reachable only by the
+ * caller, as is the case here.
+ */
+ filemap_invalidate_lock(inode->i_mapping);
+ r = mas_store_gfp(&mas, xa_mk_value(attrs), GFP_KERNEL);
+ filemap_invalidate_unlock(inode->i_mapping);
+
+ return r;
+}
+
static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
{
static const char *name = "[kvm-gmem]";
@@ -586,16 +661,9 @@ static int __kvm_gmem_create(struct kvm *kvm, loff_t size, u64 flags)
goto err_fops;
}
- inode->i_op = &kvm_gmem_iops;
- inode->i_mapping->a_ops = &kvm_gmem_aops;
- inode->i_mode |= S_IFREG;
- inode->i_size = size;
- mapping_set_gfp_mask(inode->i_mapping, GFP_HIGHUSER);
- mapping_set_inaccessible(inode->i_mapping);
- /* Unmovable mappings are supposed to be marked unevictable as well. */
- WARN_ON_ONCE(!mapping_unevictable(inode->i_mapping));
-
- GMEM_I(inode)->flags = flags;
+ err = kvm_gmem_init_inode(inode, size, flags);
+ if (err)
+ goto err_inode;
file = alloc_file_pseudo(inode, kvm_gmem_mnt, name, O_RDWR, &kvm_gmem_fops);
if (IS_ERR(file)) {
@@ -797,9 +865,13 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
if (!file)
return -EFAULT;
+ filemap_invalidate_lock_shared(file_inode(file)->i_mapping);
+
folio = __kvm_gmem_get_pfn(file, slot, index, pfn, max_order);
- if (IS_ERR(folio))
- return PTR_ERR(folio);
+ if (IS_ERR(folio)) {
+ r = PTR_ERR(folio);
+ goto out;
+ }
if (!folio_test_uptodate(folio)) {
clear_highpage(folio_page(folio, 0));
@@ -815,6 +887,8 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
else
folio_put(folio);
+out:
+ filemap_invalidate_unlock_shared(file_inode(file)->i_mapping);
return r;
}
EXPORT_SYMBOL_FOR_KVM_INTERNAL(kvm_gmem_get_pfn);
@@ -944,13 +1018,41 @@ static struct inode *kvm_gmem_alloc_inode(struct super_block *sb)
mpol_shared_policy_init(&gi->policy, NULL);
+ /*
+ * Memory attributes are protected by the filemap invalidation lock, but
+ * the lock structure isn't available at this time. Immediately mark
+ * maple tree as using external locking so that accessing the tree
+ * before it's fully initialized results in NULL pointer dereferences
+ * and not more subtle bugs.
+ */
+ mt_init_flags(&gi->attributes, MT_FLAGS_LOCK_EXTERN);
+
gi->flags = 0;
return &gi->vfs_inode;
}
static void kvm_gmem_destroy_inode(struct inode *inode)
{
- mpol_free_shared_policy(&GMEM_I(inode)->policy);
+ struct gmem_inode *gi = GMEM_I(inode);
+
+ mpol_free_shared_policy(&gi->policy);
+
+ /*
+ * Note! Checking for an empty tree is functionally necessary
+ * to avoid explosions if the tree hasn't been fully
+ * initialized, i.e. if the inode is being destroyed before
+ * guest_memfd can set the external lock, lockdep would find
+ * that the tree's internal ma_lock was not held.
+ */
+ if (!mtree_empty(&gi->attributes)) {
+ /*
+ * Acquire the invalidation lock purely to make lockdep happy,
+ * the inode is unreachable at this point.
+ */
+ filemap_invalidate_lock(inode->i_mapping);
+ __mt_destroy(&gi->attributes);
+ filemap_invalidate_unlock(inode->i_mapping);
+ }
}
static void kvm_gmem_free_inode(struct inode *inode)
--
2.53.0.851.ga537e3e6e9-goog
^ permalink raw reply related
* [PATCH RFC v3 00/43] guest_memfd: In-place conversion support
From: Ackerley Tng @ 2026-03-13 6:12 UTC (permalink / raw)
To: aik, andrew.jones, binbin.wu, brauner, chao.p.peng, david,
ira.weiny, jmattson, jroedel, jthoughton, michael.roth, oupton,
pankaj.gupta, qperret, rick.p.edgecombe, rientjes, shivankg,
steven.price, tabba, willy, wyihan, yan.y.zhao, forkloop,
pratyush, suzuki.poulose, aneesh.kumar, Paolo Bonzini,
Sean Christopherson, Thomas Gleixner, Ingo Molnar,
Borislav Petkov, Dave Hansen, x86, H. Peter Anvin, Steven Rostedt,
Masami Hiramatsu, Mathieu Desnoyers, Jonathan Corbet, Shuah Khan,
Shuah Khan, Vishal Annapurve, Jason Gunthorpe, Vlastimil Babka
Cc: kvm, linux-kernel, linux-trace-kernel, linux-doc, linux-kselftest,
Ackerley Tng
Hi,
(Here's the motivation for this series, which I realized was missing from
the earlier revisions of this series)
Up till now, guest_memfd supports the entire inode worth of memory being
used as all-shared, or all-private. CoCo VMs may request guest memory to be
converted between private and shared states, and the only way to support
that currently would be to have the userspace VMM provide two sources of
backing memory from completely different areas of physical memory.
pKVM has a use case for in-place sharing: the guest and host may be
cooperating on given data, and pKVM doesn't protect data through
encryption, so copying that given data between different areas of physical
memory as part of conversions would be unnecessary work.
This series also serves as a foundation for guest_memfd huge page
support. Now, guest_memfd only supports PAGE_SIZE pages, so if two sources
of backing memory are used, the userspace VMM could maintain a steady total
memory utilized by punching out the pages that are not used. When huge
pages are available in guest_memfd, even if the backing memory source
supports hole punching within a huge page, punching out pages to maintain
the total memory utilized by a VM would be introducing lots of
fragmentation.
In-place conversion avoids fragmentation by allowing the same physical
memory to be used for both shared and private memory, with guest_memfd
tracks the shared/private status of all the pages at a per-page
granularity.
The central principle, which guest_memfd continues to uphold, is that any
guest-private page will not be mappable to host userspace. All pages will
be mmap()-able in host userspace, but accesses to guest-private pages (as
tracked by guest_memfd) will result in a SIGBUS.
This series introduces a guest_memfd ioctl (not kvm, vm or vcpu, but
guest_memfd ioctl) that allows userspace to set memory
attributes (shared/private) directly through the guest_memfd. This is the
appropriate interface because shared/private-ness is a property of memory
and hence the request should be sent directly to the memory provider -
guest_memfd.
I'm intending RFC (v3) as a basis for discussion of flags/content
modes (name TBD) to allow userspace to request guarantees on how the memory
contents will look like after setting memory attributes. The last 6 patches
implement content mode support. These patches will be reordered, and some
of them could be absorbed into earlier patches, in later revisions.
Here are the discussion points I can think of (please add on):
1. (Might hopefully resolve soon?) Should ZERO be supported on shared to
private conversions? Discussion is at [6].
2. Do we need a CAP for userspace to query the flags/modes supported?
It seems like there won't be anything dynamic about the flags/modes
supported.
The userspace code can check what platform it is running on, and then
decide ZERO or PRESERVE based on the platform:
If the VM is running on TDX, it would want to specify ZERO all the
time. If the VM were running on pKVM it would want to specify PRESERVE
if it wants to enable in-place sharing, and ZERO if it wants to zero the
memory.
If someday TDX supports PRESERVE, then there's room for discovery of
which algorithm to choose when running the guest. Perhaps that's when
the CAP should be introduced?
3. What do people think of the structure of how various content modes are
checked for support or applied? I used overridable weak functions for
architectures that haven't defined support, and defined overrides for
x86 to show how I think it would work. For CoCo platforms, I only
implemented TDX for illustration purposes and might need help with the
other platforms. Should I have used kvm_x86_ops? I tried and found
myself defining lots of boilerplate.
4. enum for ZERO and PRESERVE?
Pros:
* No way to define both ZERO and PRESERVE (make impossible states
unrepresentable)
* e.g. enum kvm_device_type in __u32 type in struct
kvm_create_device
* But maybe someday some modes can be used together?
* Content modes is a defined axis/aspect of setting memory attributes,
having a separate field avoids having different axes of configuration
in one field. e.g. MAP_HUGETLB for mmap() is on a different axis from
MAP_PRIVATE for example
* I just used flags for this RFC since it's the most common
approach.
TODOs:
+ Let architectures override content mode handlers on a per-inode basis
since per-folio overrides means even no-ops, like ZERO on TDX, would
require iterating all the folios.
Also, in RFC v3, TEST_EXPECT_SIGBUS() is updated to assert that the default
signal handler is installed, so that developers get a clear, explicit
failure if/when something goes wrong.
This series is based on kvm/next, and here's the tree for your convenience:
https://github.com/googleprodkernel/linux-cc/commits/guest_memfd-inplace-conversion-v3
Older series:
+ RFCv2 is at [5]
+ RFCv1 is at [4]
+ Previous versions of this feature, part of other series, are available at
[1][2][3].
[1] https://lore.kernel.org/all/bd163de3118b626d1005aa88e71ef2fb72f0be0f.1726009989.git.ackerleytng@google.com/
[2] https://lore.kernel.org/all/20250117163001.2326672-6-tabba@google.com/
[3] https://lore.kernel.org/all/b784326e9ccae6a08388f1bf39db70a2204bdc51.1747264138.git.ackerleytng@google.com/
[4] https://lore.kernel.org/all/cover.1760731772.git.ackerleytng@google.com/T/
[5] https://lore.kernel.org/all/cover.1770071243.git.ackerleytng@google.com/T/
[6] https://lore.kernel.org/all/CAEvNRgFUc+9xCoN9Yo5NThHrvbccWAhPwp9nNM2fvx7QqrcJsg@mail.gmail.com/
Signed-off-by: Ackerley Tng <ackerleytng@google.com>
---
Ackerley Tng (25):
KVM: guest_memfd: Update kvm_gmem_populate() to use gmem attributes
KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2
KVM: guest_memfd: Add support for KVM_SET_MEMORY_ATTRIBUTES2
KVM: guest_memfd: Handle lru_add fbatch refcounts during conversion safety check
KVM: selftests: Update framework to use KVM_SET_MEMORY_ATTRIBUTES2
KVM: selftests: Test using guest_memfd for guest private memory
KVM: selftests: Test basic single-page conversion flow
KVM: selftests: Test conversion flow when INIT_SHARED
KVM: selftests: Test indexing in guest_memfd
KVM: selftests: Test conversion before allocation
KVM: selftests: Convert with allocated folios in different layouts
KVM: selftests: Test precision of conversion
KVM: selftests: Test that truncation does not change shared/private status
KVM: selftests: Test conversion with elevated page refcount
KVM: selftests: Reset shared memory after hole-punching
KVM: selftests: Provide function to look up guest_memfd details from gpa
KVM: selftests: Make TEST_EXPECT_SIGBUS thread-safe
KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd
KVM: selftests: Add script to exercise private_mem_conversions_test
KVM: guest_memfd: Introduce default handlers for content modes
KVM: guest_memfd: Apply content modes while setting memory attributes
KVM: x86: Add support for applying content modes
KVM: x86: Support content mode ZERO for TDX
KVM: selftests: Allow flags to be specified in set_memory_attributes functions
KVM: selftests: Update tests to use flag-enabled library functions
Sean Christopherson (18):
KVM: guest_memfd: Introduce per-gmem attributes, use to guard user mappings
KVM: Rename KVM_GENERIC_MEMORY_ATTRIBUTES to KVM_VM_MEMORY_ATTRIBUTES
KVM: Enumerate support for PRIVATE memory iff kvm_arch_has_private_mem is defined
KVM: Stub in ability to disable per-VM memory attribute tracking
KVM: guest_memfd: Wire up kvm_get_memory_attributes() to per-gmem attributes
KVM: guest_memfd: Enable INIT_SHARED on guest_memfd for x86 Coco VMs
KVM: Move KVM_VM_MEMORY_ATTRIBUTES config definition to x86
KVM: Let userspace disable per-VM mem attributes, enable per-gmem attributes
KVM: selftests: Create gmem fd before "regular" fd when adding memslot
KVM: selftests: Rename guest_memfd{,_offset} to gmem_{fd,offset}
KVM: selftests: Add support for mmap() on guest_memfd in core library
KVM: selftests: Add selftests global for guest memory attributes capability
KVM: selftests: Add helpers for calling ioctls on guest_memfd
KVM: selftests: Test that shared/private status is consistent across processes
KVM: selftests: Provide common function to set memory attributes
KVM: selftests: Check fd/flags provided to mmap() when setting up memslot
KVM: selftests: Update pre-fault test to work with per-guest_memfd attributes
KVM: selftests: Update private memory exits test work with per-gmem attributes
Documentation/virt/kvm/api.rst | 112 ++++-
arch/x86/include/asm/kvm_host.h | 2 +-
arch/x86/kvm/Kconfig | 15 +-
arch/x86/kvm/mmu/mmu.c | 4 +-
arch/x86/kvm/x86.c | 86 +++-
include/linux/kvm_host.h | 62 ++-
include/trace/events/kvm.h | 4 +-
include/uapi/linux/kvm.h | 21 +
tools/testing/selftests/kvm/.gitignore | 1 +
tools/testing/selftests/kvm/Makefile.kvm | 1 +
.../selftests/kvm/guest_memfd_conversions_test.c | 496 +++++++++++++++++++++
tools/testing/selftests/kvm/guest_memfd_test.c | 57 ++-
tools/testing/selftests/kvm/include/kvm_util.h | 136 +++++-
tools/testing/selftests/kvm/include/test_util.h | 32 +-
tools/testing/selftests/kvm/lib/kvm_util.c | 130 +++---
tools/testing/selftests/kvm/lib/test_util.c | 7 -
.../testing/selftests/kvm/pre_fault_memory_test.c | 2 +-
.../kvm/x86/private_mem_conversions_test.c | 54 ++-
.../kvm/x86/private_mem_conversions_test.py | 152 +++++++
.../selftests/kvm/x86/private_mem_kvm_exits_test.c | 36 +-
virt/kvm/Kconfig | 3 +-
virt/kvm/guest_memfd.c | 488 +++++++++++++++++++-
virt/kvm/kvm_main.c | 104 ++++-
23 files changed, 1831 insertions(+), 174 deletions(-)
---
base-commit: d2ea4ff1ce50787a98a3900b3fb1636f3620b7cf
change-id: 20260225-gmem-inplace-conversion-bd0dbd39753a
Best regards,
--
Ackerley Tng <ackerleytng@google.com>
^ permalink raw reply
* Re: [PATCH 06/15] cpufreq: Use trace_invoke_##name() at guarded tracepoint call sites
From: Viresh Kumar @ 2026-03-13 6:07 UTC (permalink / raw)
To: Vineeth Pillai (Google)
Cc: Steven Rostedt, Peter Zijlstra, Huang Rui, Gautham R. Shenoy,
Mario Limonciello, Perry Yuan, Rafael J. Wysocki,
Srinivas Pandruvada, Len Brown, linux-pm, linux-kernel,
linux-trace-kernel
In-Reply-To: <20260312150523.2054552-7-vineeth@bitbyteword.org>
On 12-03-26, 11:05, Vineeth Pillai (Google) wrote:
> Replace trace_foo() with the new trace_invoke_foo() at sites already
> guarded by trace_foo_enabled(), avoiding a redundant
> static_branch_unlikely() re-evaluation inside the tracepoint.
> trace_invoke_foo() calls the tracepoint callbacks directly without
> utilizing the static branch again.
>
> Suggested-by: Steven Rostedt <rostedt@goodmis.org>
> Suggested-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Vineeth Pillai (Google) <vineeth@bitbyteword.org>
> Assisted-by: Claude:claude-sonnet-4-6
> ---
> drivers/cpufreq/amd-pstate.c | 10 +++++-----
> drivers/cpufreq/cpufreq.c | 2 +-
> drivers/cpufreq/intel_pstate.c | 2 +-
> 3 files changed, 7 insertions(+), 7 deletions(-)
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
--
viresh
^ permalink raw reply
* [PATCH] bootconfig: Add bootconfig tests about braces
From: Masami Hiramatsu (Google) @ 2026-03-13 4:18 UTC (permalink / raw)
To: Masami Hiramatsu, Steven Rostedt
Cc: Andrew Morton, Josh Law, linux-kernel, linux-trace-kernel
In-Reply-To: <20260312191143.28719-1-objecting@objecting.org>
From: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Add more bootconfig tests for checking the error message of
non closing brace and max number of nested braces.
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
---
.../bootconfig/samples/bad-non-closed-brace.bconf | 4 ++++
tools/bootconfig/samples/bad-over-max-brace.bconf | 19 +++++++++++++++++++
.../bootconfig/samples/exp-good-nested-brace.bconf | 1 +
tools/bootconfig/samples/good-nested-brace.bconf | 18 ++++++++++++++++++
tools/bootconfig/test-bootconfig.sh | 9 +++++++++
5 files changed, 51 insertions(+)
create mode 100644 tools/bootconfig/samples/bad-non-closed-brace.bconf
create mode 100644 tools/bootconfig/samples/bad-over-max-brace.bconf
create mode 100644 tools/bootconfig/samples/exp-good-nested-brace.bconf
create mode 100644 tools/bootconfig/samples/good-nested-brace.bconf
diff --git a/tools/bootconfig/samples/bad-non-closed-brace.bconf b/tools/bootconfig/samples/bad-non-closed-brace.bconf
new file mode 100644
index 000000000000..6ed9f3363dde
--- /dev/null
+++ b/tools/bootconfig/samples/bad-non-closed-brace.bconf
@@ -0,0 +1,4 @@
+foo {
+ bar {
+ buz
+ }
diff --git a/tools/bootconfig/samples/bad-over-max-brace.bconf b/tools/bootconfig/samples/bad-over-max-brace.bconf
new file mode 100644
index 000000000000..74b5dc9e21dc
--- /dev/null
+++ b/tools/bootconfig/samples/bad-over-max-brace.bconf
@@ -0,0 +1,19 @@
+key1 {
+key2 {
+key3 {
+key4 {
+key5 {
+key6 {
+key7 {
+key8 {
+key9 {
+key10 {
+key11 {
+key12 {
+key13 {
+key14 {
+key15 {
+key16 {
+key17 {
+}}}}}}}}}}}}}}}}}
+
diff --git a/tools/bootconfig/samples/exp-good-nested-brace.bconf b/tools/bootconfig/samples/exp-good-nested-brace.bconf
new file mode 100644
index 000000000000..19e0f51b4553
--- /dev/null
+++ b/tools/bootconfig/samples/exp-good-nested-brace.bconf
@@ -0,0 +1 @@
+key1.key2.key3.key4.key5.key6.key7.key8.key9.key10.key11.key12.key13.key14.key15.key16;
diff --git a/tools/bootconfig/samples/good-nested-brace.bconf b/tools/bootconfig/samples/good-nested-brace.bconf
new file mode 100644
index 000000000000..980d094f296e
--- /dev/null
+++ b/tools/bootconfig/samples/good-nested-brace.bconf
@@ -0,0 +1,18 @@
+key1 {
+key2 {
+key3 {
+key4 {
+key5 {
+key6 {
+key7 {
+key8 {
+key9 {
+key10 {
+key11 {
+key12 {
+key13 {
+key14 {
+key15 {
+key16 {
+}}}}}}}}}}}}}}}}
+
diff --git a/tools/bootconfig/test-bootconfig.sh b/tools/bootconfig/test-bootconfig.sh
index be9bd18b1d56..fc69f815ce4a 100755
--- a/tools/bootconfig/test-bootconfig.sh
+++ b/tools/bootconfig/test-bootconfig.sh
@@ -171,6 +171,15 @@ $BOOTCONF $INITRD > $OUTFILE
xfail grep -q 'val[[:space:]]' $OUTFILE
xpass grep -q 'val2[[:space:]]' $OUTFILE
+echo "Showing correct line:column of no closing brace"
+cat > $TEMPCONF << EOF
+foo {
+bar {
+}
+EOF
+$BOOTCONF -a $TEMPCONF $INITRD 2> $OUTFILE
+xpass grep -q "1:1" $OUTFILE
+
echo "=== expected failure cases ==="
for i in samples/bad-* ; do
xfail $BOOTCONF -a $i $INITRD
^ permalink raw reply related
* Re: [PATCH v2 2/3] lib/bootconfig: check bounds before writing in __xbc_open_brace()
From: Masami Hiramatsu @ 2026-03-13 4:18 UTC (permalink / raw)
To: Josh Law
Cc: Andrew Morton, Steven Rostedt, Masami Hiramatsu, Josh Law,
linux-kernel, linux-trace-kernel
In-Reply-To: <1bd0e36d-0ea0-4a79-bbee-e38de553f1ea@gmail.com>
On Thu, 12 Mar 2026 21:30:10 +0000
Josh Law <hlcj1234567@gmail.com> wrote:
> 12 Mar 2026 21:28:11 Andrew Morton <akpm@linux-foundation.org>:
>
> > On Thu, 12 Mar 2026 21:09:52 +0000 Josh Law <hlcj1234567@gmail.com> wrote:
> >
> >>> That's a fair point, Steve. Given that brace_index isn't touched elsewhere and the current check effectively prevents the overflow, I agree this isn't strictly necessary. I'll drop this patch and stick with the fix for the off-by-one reporting error instead. Thanks for the feedback!
> >>
> >> Wait Steve,
> >> Thanks for the look. I see your point that it's currently redundant given the call patterns. It looks like Andrew has already merged this into the -mm tree, likely as a 'belt-and-suspenders' safety measure. I'll keep your feedback in mind for future cleanup, but I'm glad we got the other off-by-one fix in as well!
> >
> > Please wordwrap the emails.
> >
> >> And in my opinion, merging it is a decent idea.
> >
> > You've changed your position without explaining why?
>
> Sorry, I think it should be merged because it's better to be safe than sorry, I know there is different methods of implementation, but this one still works... I know it's churn (and I'm sorry)
I would like to keep this original >= because it is safer.
Andrew, I will pick these patches with my test patch.
Thank you,
--
Masami Hiramatsu (Google) <mhiramat@kernel.org>
^ permalink raw reply
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