Re: [PATCH 7/7] KVM: selftests: Add "delete" testcase to set_memory_region_test

[Peter Xu <peterx@redhat.com>]

On Fri, Mar 20, 2020 at 01:55:46PM -0700, Sean Christopherson wrote:
> Add coverate for running a guest with no memslots, and for deleting
> memslots while the guest is running.  Enhance the test to use, and
> expect, a unique value for MMIO reads, e.g. to verify each stage of
> the test.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> ---
>  .../kvm/x86_64/set_memory_region_test.c       | 122 ++++++++++++++++--
>  1 file changed, 108 insertions(+), 14 deletions(-)
> 
> diff --git a/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c b/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
> index c6691cff4e19..44aed8ac932b 100644
> --- a/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
> +++ b/tools/testing/selftests/kvm/x86_64/set_memory_region_test.c
> @@ -26,42 +26,109 @@
>  #define MEM_REGION_SIZE		0x200000
>  #define MEM_REGION_SLOT		10
>  
> -static void guest_code(void)
> +static const uint64_t MMIO_VAL = 0xbeefull;
> +
> +extern const uint64_t final_rip_start;
> +extern const uint64_t final_rip_end;
> +
> +static inline uint64_t guest_spin_on_val(uint64_t spin_val)
>  {
>  	uint64_t val;
>  
>  	do {
>  		val = READ_ONCE(*((uint64_t *)MEM_REGION_GPA));
> -	} while (!val);
> +	} while (val == spin_val);
> +	return val;
> +}
>  
> -	if (val != 1)
> -		ucall(UCALL_ABORT, 1, val);
> +static void guest_code(void)
> +{
> +	uint64_t val;
>  
> -	GUEST_DONE();
> +	/*
> +	 * Spin until the memory region is moved to a misaligned address.  This
> +	 * may or may not trigger MMIO, as the window where the memslot is
> +	 * invalid is quite small.
> +	 */
> +	val = guest_spin_on_val(0);
> +	GUEST_ASSERT(val == 1 || val == MMIO_VAL);
> +
> +	/* Spin until the memory region is realigned. */
> +	GUEST_ASSERT(guest_spin_on_val(MMIO_VAL) == 1);

IIUC ideally we should do GUEST_SYNC() after each GUEST_ASSERT() to
make sure the two threads are in sync.  Otherwise e.g. there's no
guarantee that the main thread won't run too fast to quickly remove
the memslot and re-add it back before the guest_spin_on_val() starts
above, then the assert could trigger when it reads the value as zero.

> +
> +	/* Spin until the memory region is deleted. */
> +	GUEST_ASSERT(guest_spin_on_val(1) == MMIO_VAL);
> +
> +	/* Spin until the memory region is recreated. */
> +	GUEST_ASSERT(guest_spin_on_val(MMIO_VAL) == 0);
> +
> +	/* Spin until the memory region is deleted. */
> +	GUEST_ASSERT(guest_spin_on_val(0) == MMIO_VAL);
> +
> +	asm("1:\n\t"
> +	    ".pushsection .rodata\n\t"
> +	    ".global final_rip_start\n\t"
> +	    "final_rip_start: .quad 1b\n\t"
> +	    ".popsection");
> +
> +	/* Spin indefinitely (until the code memslot is deleted). */
> +	guest_spin_on_val(MMIO_VAL);
> +
> +	asm("1:\n\t"
> +	    ".pushsection .rodata\n\t"
> +	    ".global final_rip_end\n\t"
> +	    "final_rip_end: .quad 1b\n\t"
> +	    ".popsection");
> +
> +	GUEST_ASSERT(0);
>  }
>  
>  static void *vcpu_worker(void *data)
>  {
>  	struct kvm_vm *vm = data;
> +	struct kvm_regs regs;
>  	struct kvm_run *run;
>  	struct ucall uc;
> -	uint64_t cmd;
>  
>  	/*
>  	 * Loop until the guest is done.  Re-enter the guest on all MMIO exits,
> -	 * which will occur if the guest attempts to access a memslot while it
> -	 * is being moved.
> +	 * which will occur if the guest attempts to access a memslot after it
> +	 * has been deleted or while it is being moved .
>  	 */
>  	run = vcpu_state(vm, VCPU_ID);
> -	do {
> +
> +	memcpy(run->mmio.data, &MMIO_VAL, 8);
> +	while (1) {
>  		vcpu_run(vm, VCPU_ID);
> -	} while (run->exit_reason == KVM_EXIT_MMIO);
> +		if (run->exit_reason != KVM_EXIT_MMIO)
> +			break;
>  
> -	TEST_ASSERT(run->exit_reason == KVM_EXIT_IO,
> +		TEST_ASSERT(!run->mmio.is_write, "Unexpected exit mmio write");
> +		TEST_ASSERT(run->mmio.len == 8,
> +			    "Unexpected exit mmio size = %u", run->mmio.len);
> +
> +		TEST_ASSERT(run->mmio.phys_addr == MEM_REGION_GPA,
> +			    "Unexpected exit mmio address = 0x%llx",
> +			    run->mmio.phys_addr);
> +	}
> +
> +	if (run->exit_reason == KVM_EXIT_IO) {
> +		(void)get_ucall(vm, VCPU_ID, &uc);
> +		TEST_FAIL("%s at %s:%ld",
> +			  (const char *)uc.args[0], __FILE__, uc.args[1]);
> +	}
> +
> +	TEST_ASSERT(run->exit_reason == KVM_EXIT_SHUTDOWN ||
> +		    run->exit_reason == KVM_INTERNAL_ERROR_EMULATION,
>  		    "Unexpected exit reason = %d", run->exit_reason);
>  
> -	cmd = get_ucall(vm, VCPU_ID, &uc);
> -	TEST_ASSERT(cmd == UCALL_DONE, "Unexpected val in guest = %lu", uc.args[0]);
> +	vcpu_regs_get(vm, VCPU_ID, &regs);
> +
> +	TEST_ASSERT(regs.rip >= final_rip_start &&
> +		    regs.rip < final_rip_end,
> +		    "Bad rip, expected 0x%lx - 0x%lx, got 0x%llx\n",
> +		    final_rip_start, final_rip_end, regs.rip);
> +
>  	return NULL;
>  }
>  
> @@ -72,6 +139,13 @@ static void test_move_memory_region(void)
>  	uint64_t *hva;
>  	uint64_t gpa;
>  
> +	vm = vm_create(VM_MODE_DEFAULT, 0, O_RDWR);
> +	vm_vcpu_add(vm, VCPU_ID);
> +	/* Fails with ENOSPC because the MMU can't create pages (no slots). */
> +	TEST_ASSERT(_vcpu_run(vm, VCPU_ID) == -1 && errno == ENOSPC,
> +		    "Unexpected error code = %d", errno);
> +	kvm_vm_free(vm);
> +
>  	vm = vm_create_default(VCPU_ID, 0, guest_code);
>  
>  	vcpu_set_cpuid(vm, VCPU_ID, kvm_get_supported_cpuid());
> @@ -105,7 +179,6 @@ static void test_move_memory_region(void)
>  	 */
>  	vm_mem_region_move(vm, MEM_REGION_SLOT, MEM_REGION_GPA - 4096);
>  	WRITE_ONCE(*hva, 2);
> -
>  	usleep(100000);
>  
>  	/*
> @@ -116,6 +189,27 @@ static void test_move_memory_region(void)
>  
>  	/* Restore the original base, the guest should see "1". */
>  	vm_mem_region_move(vm, MEM_REGION_SLOT, MEM_REGION_GPA);
> +	usleep(100000);
> +
> +	/* Delete the memory region, the guest should not die. */
> +	vm_mem_region_delete(vm, MEM_REGION_SLOT);
> +	usleep(100000);
> +
> +	/* Recreate the memory region.  The guest should see "0". */
> +	vm_userspace_mem_region_add(vm, VM_MEM_SRC_ANONYMOUS_THP,
> +				    MEM_REGION_GPA, MEM_REGION_SLOT,
> +				    MEM_REGION_SIZE / getpagesize(), 0);
> +	usleep(100000);
> +
> +	/* Delete the region again so that there's only one memslot left. */
> +	vm_mem_region_delete(vm, MEM_REGION_SLOT);
> +	usleep(100000);
> +
> +	/*
> +	 * Delete the primary memslot.  This should cause an emulation error or
> +	 * shutdown due to the page tables getting nuked.
> +	 */
> +	vm_mem_region_delete(vm, VM_PRIMARY_MEM_SLOT);
>  
>  	pthread_join(vcpu_thread, NULL);
>  
> -- 
> 2.24.1
> 

-- 
Peter Xu