2023-09-22 04:28:07

by Isaku Yamahata

Subject: [RFC PATCH v2 3/6] KVM: selftests: Add tests for punch hole on guest_memfd

From: Isaku Yamahata <[email protected]>

Punch hole implies the region is zeroed out. Add tests if the punched
region has zero.
Oppertunistically Remove unused member, pattern, in guest_run_test().

Signed-off-by: Isaku Yamahata <[email protected]>
---
.../kvm/x86_64/private_mem_conversions_test.c | 26 ++++++++++++++-----
1 file changed, 20 insertions(+), 6 deletions(-)

diff --git a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
index 50541246d6fd..c05c725645af 100644
--- a/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
+++ b/tools/testing/selftests/kvm/x86_64/private_mem_conversions_test.c
@@ -85,9 +85,10 @@ static void guest_sync_private(uint64_t gpa, uint64_t size, uint8_t pattern)
/* Arbitrary values, KVM doesn't care about the attribute flags. */
#define MAP_GPA_SHARED BIT(0)
#define MAP_GPA_DO_FALLOCATE BIT(1)
+#define MAP_GPA_FALLOCATE_ONLY BIT(2)

static void guest_map_mem(uint64_t gpa, uint64_t size, bool map_shared,
- bool do_fallocate)
+ bool do_fallocate, bool fallocate_only)
{
uint64_t flags = 0;

@@ -95,17 +96,24 @@ static void guest_map_mem(uint64_t gpa, uint64_t size, bool map_shared,
flags |= MAP_GPA_SHARED;
if (do_fallocate)
flags |= MAP_GPA_DO_FALLOCATE;
+ if (fallocate_only)
+ flags |= MAP_GPA_FALLOCATE_ONLY;
kvm_hypercall_map_gpa_range(gpa, size, flags);
}

static void guest_map_shared(uint64_t gpa, uint64_t size, bool do_fallocate)
{
- guest_map_mem(gpa, size, true, do_fallocate);
+ guest_map_mem(gpa, size, true, do_fallocate, false);
}

static void guest_map_private(uint64_t gpa, uint64_t size, bool do_fallocate)
{
- guest_map_mem(gpa, size, false, do_fallocate);
+ guest_map_mem(gpa, size, false, do_fallocate, false);
+}
+
+static void guest_punch_hole_private(uint64_t gpa, uint64_t size)
+{
+ guest_map_mem(gpa, size, true, true, true);
}

static void guest_run_test(uint64_t base_gpa, bool do_fallocate)
@@ -113,7 +121,6 @@ static void guest_run_test(uint64_t base_gpa, bool do_fallocate)
struct {
uint64_t offset;
uint64_t size;
- uint8_t pattern;
} stages[] = {
GUEST_STAGE(0, PAGE_SIZE),
GUEST_STAGE(0, SZ_2M),
@@ -156,6 +163,10 @@ static void guest_run_test(uint64_t base_gpa, bool do_fallocate)

if (size > PAGE_SIZE) {
memset((void *)gpa, p2, PAGE_SIZE);
+
+ /* Test if punch hole results in zeroing page. */
+ guest_punch_hole_private(gpa, PAGE_SIZE);
+ memcmp_g(gpa, 0, PAGE_SIZE);
goto skip;
}

@@ -229,6 +240,7 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
uint64_t size = run->hypercall.args[1] * PAGE_SIZE;
bool map_shared = run->hypercall.args[2] & MAP_GPA_SHARED;
bool do_fallocate = run->hypercall.args[2] & MAP_GPA_DO_FALLOCATE;
+ bool fallocate_only = run->hypercall.args[2] & MAP_GPA_FALLOCATE_ONLY;
struct kvm_vm *vm = vcpu->vm;

TEST_ASSERT(run->hypercall.nr == KVM_HC_MAP_GPA_RANGE,
@@ -238,8 +250,10 @@ static void handle_exit_hypercall(struct kvm_vcpu *vcpu)
if (do_fallocate)
vm_guest_mem_fallocate(vm, gpa, size, map_shared);

- vm_set_memory_attributes(vm, gpa, size,
- map_shared ? 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
+ if (!fallocate_only)
+ vm_set_memory_attributes(vm, gpa, size,
+ map_shared ?
+ 0 : KVM_MEMORY_ATTRIBUTE_PRIVATE);
run->hypercall.ret = 0;
}

--
2.25.1

2023-09-22 19:04:13

by Sean Christopherson

Subject: Re: [RFC PATCH v2 3/6] KVM: selftests: Add tests for punch hole on guest_memfd

On Thu, Sep 21, 2023, [email protected] wrote:
> From: Isaku Yamahata <[email protected]>
>
> Punch hole implies the region is zeroed out. Add tests if the punched
> region has zero.
> Oppertunistically Remove unused member, pattern, in guest_run_test().

Heh, I didn't pretty much all the same stuff, except I opted to have
SET_ATTRIBUTE instead of FALLOCATE_ONLY, e.g. in case we end up with a test that's
wants a thrid flavor (or somehow neither?).

> Signed-off-by: Isaku Yamahata <[email protected]>
> ---
> .../kvm/x86_64/private_mem_conversions_test.c | 26 ++++++++++++++-----
> 1 file changed, 20 insertions(+), 6 deletions(-)
>

...

> @@ -156,6 +163,10 @@ static void guest_run_test(uint64_t base_gpa, bool do_fallocate)
>
> if (size > PAGE_SIZE) {
> memset((void *)gpa, p2, PAGE_SIZE);
> +
> + /* Test if punch hole results in zeroing page. */
> + guest_punch_hole_private(gpa, PAGE_SIZE);
> + memcmp_g(gpa, 0, PAGE_SIZE);

I added a dedicated sub-test to provide a bit more variety in the tests. I highly
doubt my version will ever find a bug that isn't caught by this approach, but if
nothing else, it's nice to have a completely separate sub-test.