* Wei Yang (richardw.y...@linux.intel.com) wrote:
> On Tue, Oct 08, 2019 at 06:24:23PM +0100, Dr. David Alan Gilbert wrote:
> >* Wei Yang (richardw.y...@linux.intel.com) wrote:
> >> postcopy_ram_incoming_setup() and postcopy_ram_incoming_cleanup() are
> >> counterpart. It is reasonable to map/unmap large zero page in these two
> >> functions respectively.
> >>
> >> Signed-off-by: Wei Yang <richardw.y...@linux.intel.com>
> >
> >Yes, OK.
> >
> >> ---
> >> migration/postcopy-ram.c | 34 +++++++++++++++++-----------------
> >> 1 file changed, 17 insertions(+), 17 deletions(-)
> >>
> >> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
> >> index e554f93eec..813cfa5c42 100644
> >> --- a/migration/postcopy-ram.c
> >> +++ b/migration/postcopy-ram.c
> >> @@ -1142,6 +1142,22 @@ int
> >> postcopy_ram_incoming_setup(MigrationIncomingState *mis)
> >> return -1;
> >> }
> >>
> >> + /*
> >> + * Map large zero page when kernel can't use UFFDIO_ZEROPAGE for
> >> hugepages
> >> + */
> >> + mis->postcopy_tmp_zero_page = mmap(NULL, mis->largest_page_size,
> >> + PROT_READ | PROT_WRITE,
> >> + MAP_PRIVATE | MAP_ANONYMOUS,
> >> + -1, 0);
> >> + if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
> >> + int e = errno;
> >> + mis->postcopy_tmp_zero_page = NULL;
> >> + error_report("%s: Failed to map large zero page %s",
> >> + __func__, strerror(e));
> >> + return -e;
> >
> >Note this starts returning -errno where the rest of this function
> >returns 0 or -1; returning -errno is a good thing I think and it might
> >be good to change the other returns.
> >
>
> This is reasonable, while I am thinking how caller would handle this.
>
> For example, the return value would be finally returned to
> qemu_loadvm_state_main(). If we handle each errno respectively in this
> function, the code would be difficult to read and maintain.
>
> Would it be good to classify return value to different category? Like
>
> POSTCOPY_FATAL
> POSTCOPY_RETRY
> POSTCOPY_DISABLE
It's actually quite difficult because unix errno's are too simple;
an EIO has too many causes.
ideally we'd like to be able to separate out a network transport error
that occurs during the postcopy phase for recovery and make sure
that we don't confuse that with any other error.
Dave
>
> >
> >Reviewed-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> >
> >> + }
> >> + memset(mis->postcopy_tmp_zero_page, '\0', mis->largest_page_size);
> >> +
> >> /*
> >> * Ballooning can mark pages as absent while we're postcopying
> >> * that would cause false userfaults.
> >> @@ -1248,23 +1264,7 @@ int postcopy_place_page_zero(MigrationIncomingState
> >> *mis, void *host,
> >> qemu_ram_block_host_offset(rb,
> >>
> >> host));
> >> } else {
> >> - /* The kernel can't use UFFDIO_ZEROPAGE for hugepages */
> >> - if (!mis->postcopy_tmp_zero_page) {
> >> - mis->postcopy_tmp_zero_page = mmap(NULL,
> >> mis->largest_page_size,
> >> - PROT_READ | PROT_WRITE,
> >> - MAP_PRIVATE |
> >> MAP_ANONYMOUS,
> >> - -1, 0);
> >> - if (mis->postcopy_tmp_zero_page == MAP_FAILED) {
> >> - int e = errno;
> >> - mis->postcopy_tmp_zero_page = NULL;
> >> - error_report("%s: %s mapping large zero page",
> >> - __func__, strerror(e));
> >> - return -e;
> >> - }
> >> - memset(mis->postcopy_tmp_zero_page, '\0',
> >> mis->largest_page_size);
> >> - }
> >> - return postcopy_place_page(mis, host, mis->postcopy_tmp_zero_page,
> >> - rb);
> >> + return postcopy_place_page(mis, host,
> >> mis->postcopy_tmp_zero_page, rb);
> >> }
> >> }
> >>
> >> --
> >> 2.17.1
> >>
> >--
> >Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
>
> --
> Wei Yang
> Help you, Help me
--
Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
