Commit ef4c9f4f authored by David Matlack's avatar David Matlack Committed by Paolo Bonzini
Browse files

KVM: selftests: Fix 32-bit truncation of vm_get_max_gfn() 



vm_get_max_gfn() casts vm->max_gfn from a uint64_t to an unsigned int,
which causes the upper 32-bits of the max_gfn to get truncated.

Nobody noticed until now likely because vm_get_max_gfn() is only used
as a mechanism to create a memslot in an unused region of the guest
physical address space (the top), and the top of the 32-bit physical
address space was always good enough.

This fix reveals a bug in memslot_modification_stress_test which was
trying to create a dummy memslot past the end of guest physical memory.
Fix that by moving the dummy memslot lower.

Fixes: 52200d0d ("KVM: selftests: Remove duplicate guest mode handling")
Reviewed-by: default avatarVenkatesh Srinivas <venkateshs@chromium.org>
Signed-off-by: default avatarDavid Matlack <dmatlack@google.com>
Message-Id: <20210521173828.1180619-1-dmatlack@google.com>
Reviewed-by: default avatarAndrew Jones <drjones@redhat.com>
Reviewed-by: default avatarPeter Xu <peterx@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent cad347fa

tools/testing/selftests/kvm/include/kvm_util.h

+1 −1
Original line number Diff line number Diff line
@@ -302,7 +302,7 @@ bool vm_is_unrestricted_guest(struct kvm_vm *vm); 


unsigned int vm_get_page_size(struct kvm_vm *vm);

unsigned int vm_get_page_shift(struct kvm_vm *vm);

unsigned int vm_get_max_gfn(struct kvm_vm *vm);

uint64_t vm_get_max_gfn(struct kvm_vm *vm);

int vm_get_fd(struct kvm_vm *vm);



unsigned int vm_calc_num_guest_pages(enum vm_guest_mode mode, size_t size);

tools/testing/selftests/kvm/lib/kvm_util.c

+1 −1
Original line number Diff line number Diff line
@@ -2117,7 +2117,7 @@ unsigned int vm_get_page_shift(struct kvm_vm *vm) 
	return vm->page_shift;

}



unsigned int vm_get_max_gfn(struct kvm_vm *vm)

uint64_t vm_get_max_gfn(struct kvm_vm *vm)

{

	return vm->max_gfn;

}

tools/testing/selftests/kvm/lib/perf_test_util.c

+3 −1
Original line number Diff line number Diff line
@@ -2,6 +2,7 @@ 
/*

 * Copyright (C) 2020, Google LLC.

 */

#include <inttypes.h>



#include "kvm_util.h"

#include "perf_test_util.h"
@@ -80,7 +81,8 @@ struct kvm_vm *perf_test_create_vm(enum vm_guest_mode mode, int vcpus, 
	 */

	TEST_ASSERT(guest_num_pages < vm_get_max_gfn(vm),

		    "Requested more guest memory than address space allows.\n"

		    "    guest pages: %lx max gfn: %x vcpus: %d wss: %lx]\n",

		    "    guest pages: %" PRIx64 " max gfn: %" PRIx64

		    " vcpus: %d wss: %" PRIx64 "]\n",

		    guest_num_pages, vm_get_max_gfn(vm), vcpus,

		    vcpu_memory_bytes);

tools/testing/selftests/kvm/memslot_modification_stress_test.c

+11 −7
Original line number Diff line number Diff line
@@ -71,14 +71,22 @@ struct memslot_antagonist_args { 
};



static void add_remove_memslot(struct kvm_vm *vm, useconds_t delay,

			      uint64_t nr_modifications, uint64_t gpa)

			       uint64_t nr_modifications)

{

	const uint64_t pages = 1;

	uint64_t gpa;

	int i;



	/*

	 * Add the dummy memslot just below the perf_test_util memslot, which is

	 * at the top of the guest physical address space.

	 */

	gpa = guest_test_phys_mem - pages * vm_get_page_size(vm);



	for (i = 0; i < nr_modifications; i++) {

		usleep(delay);

		vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS, gpa,

					    DUMMY_MEMSLOT_INDEX, 1, 0);

					    DUMMY_MEMSLOT_INDEX, pages, 0);



		vm_mem_region_delete(vm, DUMMY_MEMSLOT_INDEX);

	}
@@ -120,11 +128,7 @@ static void run_test(enum vm_guest_mode mode, void *arg) 
	pr_info("Started all vCPUs\n");



	add_remove_memslot(vm, p->memslot_modification_delay,

			   p->nr_memslot_modifications,

			   guest_test_phys_mem +

			   (guest_percpu_mem_size * nr_vcpus) +

			   perf_test_args.host_page_size +

			   perf_test_args.guest_page_size);

			   p->nr_memslot_modifications);



	run_vcpus = false;