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Date: Tue, 30 Jul 2019 16:57:33 +0200
From: Christian Borntraeger <borntraeger@...ibm.com>
To: Thomas Huth <thuth@...hat.com>, kvm@...r.kernel.org,
Janosch Frank <frankja@...ux.ibm.com>
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-s390@...r.kernel.org, David Hildenbrand <david@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Radim Krčmář <rkrcmar@...hat.com>,
Shuah Khan <shuah@...nel.org>, Peter Xu <peterx@...hat.com>
Subject: Re: [PATCH 2/2] KVM: selftests: Enable dirty_log_test on s390x
On 30.07.19 12:01, Thomas Huth wrote:
> To run the dirty_log_test on s390x, we have to make sure that we
> access the dirty log bitmap with little endian byte ordering and
> we have to properly align the memslot of the guest.
> Also all dirty bits of a segment are set once on s390x when one
> of the pages of a segment are written to for the first time, so
> we have to make sure that we touch all pages during the first
> iteration to keep the test in sync here.
While this fixes the test (and the migration does work fine), it still
means that s390x overindicates the dirty bit for sparsely populated
1M segments. It is just a performance issue, but maybe we should try
to get this fixed. Not sure what to do here to remember us about this,
adding this as expected fail?
>
> Signed-off-by: Thomas Huth <thuth@...hat.com>
> ---
> tools/testing/selftests/kvm/Makefile | 1 +
> tools/testing/selftests/kvm/dirty_log_test.c | 70 ++++++++++++++++++--
> 2 files changed, 66 insertions(+), 5 deletions(-)
>
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index ba7849751989..ac7e63e00fee 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -33,6 +33,7 @@ TEST_GEN_PROGS_aarch64 += dirty_log_test
> TEST_GEN_PROGS_aarch64 += kvm_create_max_vcpus
>
> TEST_GEN_PROGS_s390x += s390x/sync_regs_test
> +TEST_GEN_PROGS_s390x += dirty_log_test
> TEST_GEN_PROGS_s390x += kvm_create_max_vcpus
>
> TEST_GEN_PROGS += $(TEST_GEN_PROGS_$(UNAME_M))
> diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
> index ceb52b952637..7a1223ad0ff3 100644
> --- a/tools/testing/selftests/kvm/dirty_log_test.c
> +++ b/tools/testing/selftests/kvm/dirty_log_test.c
> @@ -26,9 +26,22 @@
> /* The memory slot index to track dirty pages */
> #define TEST_MEM_SLOT_INDEX 1
>
> +#ifdef __s390x__
> +
> +/*
> + * On s390x, the ELF program is sometimes linked at 0x80000000, so we can
> + * not use 0x40000000 here without overlapping into that region. Thus let's
> + * use 0xc0000000 as base address there instead.
> + */
> +#define DEFAULT_GUEST_TEST_MEM 0xc0000000
> +
> +#else
> +
> /* Default guest test memory offset, 1G */
> #define DEFAULT_GUEST_TEST_MEM 0x40000000
>
> +#endif
> +
> /* How many pages to dirty for each guest loop */
> #define TEST_PAGES_PER_LOOP 1024
>
> @@ -38,6 +51,27 @@
> /* Interval for each host loop (ms) */
> #define TEST_HOST_LOOP_INTERVAL 10UL
>
> +/* Dirty bitmaps are always little endian, so we need to swap on big endian */
> +#if defined(__s390x__)
> +# define BITOP_LE_SWIZZLE ((BITS_PER_LONG-1) & ~0x7)
> +# define test_bit_le(nr, addr) \
> + test_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
> +# define set_bit_le(nr, addr) \
> + set_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
> +# define clear_bit_le(nr, addr) \
> + clear_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
> +# define test_and_set_bit_le(nr, addr) \
> + test_and_set_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
> +# define test_and_clear_bit_le(nr, addr) \
> + test_and_clear_bit((nr) ^ BITOP_LE_SWIZZLE, addr)
> +#else
> +# define test_bit_le test_bit
> +# define set_bit_le set_bit
> +# define clear_bit_le clear_bit
> +# define test_and_set_bit_le test_and_set_bit
> +# define test_and_clear_bit_le test_and_clear_bit
> +#endif
> +
> /*
> * Guest/Host shared variables. Ensure addr_gva2hva() and/or
> * sync_global_to/from_guest() are used when accessing from
> @@ -69,11 +103,25 @@ static uint64_t guest_test_virt_mem = DEFAULT_GUEST_TEST_MEM;
> */
> static void guest_code(void)
> {
> + uint64_t addr;
> int i;
>
> +#ifdef __s390x__
> + /*
> + * On s390x, all pages of a 1M segment are initially marked as dirty
> + * when a page of the segment is written to for the very first time.
> + * To compensate this specialty in this test, we need to touch all
> + * pages during the first iteration.
> + */
> + for (i = 0; i < guest_num_pages; i++) {
> + addr = guest_test_virt_mem + i * guest_page_size;
> + *(uint64_t *)addr = READ_ONCE(iteration);
> + }
> +#endif
> +
> while (true) {
> for (i = 0; i < TEST_PAGES_PER_LOOP; i++) {
> - uint64_t addr = guest_test_virt_mem;
> + addr = guest_test_virt_mem;
> addr += (READ_ONCE(random_array[i]) % guest_num_pages)
> * guest_page_size;
> addr &= ~(host_page_size - 1);
> @@ -158,15 +206,15 @@ static void vm_dirty_log_verify(unsigned long *bmap)
> value_ptr = host_test_mem + page * host_page_size;
>
> /* If this is a special page that we were tracking... */
> - if (test_and_clear_bit(page, host_bmap_track)) {
> + if (test_and_clear_bit_le(page, host_bmap_track)) {
> host_track_next_count++;
> - TEST_ASSERT(test_bit(page, bmap),
> + TEST_ASSERT(test_bit_le(page, bmap),
> "Page %"PRIu64" should have its dirty bit "
> "set in this iteration but it is missing",
> page);
> }
>
> - if (test_bit(page, bmap)) {
> + if (test_bit_le(page, bmap)) {
> host_dirty_count++;
> /*
> * If the bit is set, the value written onto
> @@ -209,7 +257,7 @@ static void vm_dirty_log_verify(unsigned long *bmap)
> * should report its dirtyness in the
> * next run
> */
> - set_bit(page, host_bmap_track);
> + set_bit_le(page, host_bmap_track);
> }
> }
> }
> @@ -293,6 +341,10 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
> * case where the size is not aligned to 64 pages.
> */
> guest_num_pages = (1ul << (30 - guest_page_shift)) + 16;
> +#ifdef __s390x__
> + /* Round up to multiple of 1M (segment size) */
> + guest_num_pages = (guest_num_pages + 0xff) & ~0xffUL;
> +#endif
> host_page_size = getpagesize();
> host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
> !!((guest_num_pages * guest_page_size) % host_page_size);
> @@ -304,6 +356,11 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
> guest_test_phys_mem = phys_offset;
> }
>
> +#ifdef __s390x__
> + /* Align to 1M (segment size) */
> + guest_test_phys_mem &= ~((1 << 20) - 1);
> +#endif
> +
> DEBUG("guest physical test memory offset: 0x%lx\n", guest_test_phys_mem);
>
> bmap = bitmap_alloc(host_num_pages);
> @@ -454,6 +511,9 @@ int main(int argc, char *argv[])
> vm_guest_mode_params_init(VM_MODE_P48V48_64K, true, true);
> }
> #endif
> +#ifdef __s390x__
> + vm_guest_mode_params_init(VM_MODE_P40V48_4K, true, true);
> +#endif
>
> while ((opt = getopt(argc, argv, "hi:I:p:m:")) != -1) {
> switch (opt) {
>
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