| Message ID | 20230117220914.2062125-21-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | migration: Support hugetlb doublemaps | expand |
Peter Xu <peterx@redhat.com> wrote: > Teach QEMU to be able to handle page faults using UFFDIO_CONTINUE for > hugetlbfs double mapped ranges. > > To copy the data, we need to use the mirror buffer created per ramblock by > a raw memcpy(), then we can kick the faulted threads using UFFDIO_CONTINUE > by installing the pgtables. > > Move trace_postcopy_place_page(host) upper so that it'll dump something for > either UFFDIO_COPY or UFFDIO_CONTINUE. > > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > migration/postcopy-ram.c | 55 ++++++++++++++++++++++++++++++++++++++-- > migration/trace-events | 4 +-- > 2 files changed, 55 insertions(+), 4 deletions(-) > > diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c > index 8a2259581e..c4bd338e22 100644 > --- a/migration/postcopy-ram.c > +++ b/migration/postcopy-ram.c > @@ -1350,6 +1350,43 @@ int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset) > return 0; > } > > +/* Returns the mirror_host addr for a specific host address in ramblock */ > +static inline void *migration_ram_get_mirror_addr(RAMBlock *rb, void *host) > +{ > + return (void *)((__u64)rb->host_mirror + ((__u64)host - (__u64)rb->host)); This is gross :-( I hate this C miss-feature. What about: return (char *)rb->host_mirror + (char*)host - (char*)rb->host; But I don't know if it (much) clearer. And no, I don't remember if we ever need more parents. gcc used to do "the right" thing on void * arithmetic, but it is not in the standard, and I don't know what is worse. > +} > + > +static int > +qemu_uffd_continue(MigrationIncomingState *mis, RAMBlock *rb, void *host, > + void *from) > +{ > + void *mirror_addr = migration_ram_get_mirror_addr(rb, host); > + /* Doublemap uses small host page size */ > + uint64_t psize = qemu_real_host_page_size(); > + struct uffdio_continue req; > + > + /* > + * Copy data first into the mirror host pointer; we can't directly copy > + * data into rb->host because otherwise our thread will get trapped too. > + */ > + memcpy(mirror_addr, from, psize); > + > + /* Kick off the faluted threads to fetch data from the page cache ^^^^^^^ > */ Faulted > + req.range.start = (__u64)host; > + req.range.len = psize; > + req.mode = 0; > + if (ioctl(mis->userfault_fd, UFFDIO_CONTINUE, &req)) { > + error_report("%s: UFFDIO_CONTINUE failed for start=%p" > + " len=0x%"PRIx64": %s\n", __func__, host, > + psize, strerror(-req.mapped)); > + return req.mapped; > + } > + > + postcopy_mark_received(mis, rb, host, psize / qemu_target_page_size()); > + > + return 0; > +} > + > /* > * Place a host page (from) at (host) atomically > * returns 0 on success > @@ -1359,6 +1396,18 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, > { > size_t pagesize = migration_ram_pagesize(rb); > > + trace_postcopy_place_page(rb->idstr, (uint8_t *)host - rb->host, host); > + > + if (postcopy_use_minor_fault(rb)) { > + /* > + * If minor fault used, we use UFFDIO_CONTINUE instead. > + * > + * TODO: support shared uffds (e.g. vhost-user). Currently we're > + * skipping them. > + */ > + return qemu_uffd_continue(mis, rb, host, from); > + } > + > /* copy also acks to the kernel waking the stalled thread up > * TODO: We can inhibit that ack and only do it if it was requested > * which would be slightly cheaper, but we'd have to be careful > @@ -1372,7 +1421,6 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, > return -e; > } > > - trace_postcopy_place_page(host); > return postcopy_notify_shared_wake(rb, > qemu_ram_block_host_offset(rb, host)); > } > @@ -1385,10 +1433,13 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, > RAMBlock *rb) > { > size_t pagesize = migration_ram_pagesize(rb); > - trace_postcopy_place_page_zero(host); > + trace_postcopy_place_page_zero(rb->idstr, (uint8_t *)host - rb->host, host); It is me, or to be standard compliant, you need to cast also rb->host? > /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE > * but it's not available for everything (e.g. hugetlbpages) > + * > + * NOTE: when hugetlb double-map enabled, then this ramblock will never > + * have RAM_UF_ZEROPAGE, so it'll always go to postcopy_place_page(). > */ > if (qemu_ram_is_uf_zeroable(rb)) { > if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) { > diff --git a/migration/trace-events b/migration/trace-events > index 6b418a0e9e..7baf235d22 100644 > --- a/migration/trace-events > +++ b/migration/trace-events > @@ -265,8 +265,8 @@ postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned > postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" > postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" > postcopy_nhp_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" > -postcopy_place_page(void *host_addr) "host=%p" > -postcopy_place_page_zero(void *host_addr) "host=%p" > +postcopy_place_page(const char *id, size_t offset, void *host_addr) "id=%s offset=0x%zx host=%p" > +postcopy_place_page_zero(const char *id, size_t offset, void *host_addr) "id=%s offset=0x%zx host=%p" > postcopy_ram_enable_notify(void) "" > mark_postcopy_blocktime_begin(uint64_t addr, void *dd, uint32_t time, int cpu, int received) "addr: 0x%" PRIx64 ", dd: %p, time: %u, cpu: %d, already_received: %d" > mark_postcopy_blocktime_end(uint64_t addr, void *dd, uint32_t time, int affected_cpu) "addr: 0x%" PRIx64 ", dd: %p, time: %u, affected_cpu: %d" I think that you can split the part of the patch that changes the traces. But again, it is up to you.
Juan Quintela <quintela@redhat.com> wrote: > Peter Xu <peterx@redhat.com> wrote: >> Teach QEMU to be able to handle page faults using UFFDIO_CONTINUE for >> hugetlbfs double mapped ranges. >> >> To copy the data, we need to use the mirror buffer created per ramblock by >> a raw memcpy(), then we can kick the faulted threads using UFFDIO_CONTINUE >> by installing the pgtables. >> >> Move trace_postcopy_place_page(host) upper so that it'll dump something for >> either UFFDIO_COPY or UFFDIO_CONTINUE. >> >> Signed-off-by: Peter Xu <peterx@redhat.com> > >> --- >> migration/postcopy-ram.c | 55 ++++++++++++++++++++++++++++++++++++++-- >> migration/trace-events | 4 +-- >> 2 files changed, 55 insertions(+), 4 deletions(-) >> >> diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c >> index 8a2259581e..c4bd338e22 100644 >> --- a/migration/postcopy-ram.c >> +++ b/migration/postcopy-ram.c >> @@ -1350,6 +1350,43 @@ int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset) >> return 0; >> } >> >> +/* Returns the mirror_host addr for a specific host address in ramblock */ >> +static inline void *migration_ram_get_mirror_addr(RAMBlock *rb, void *host) >> +{ >> + return (void *)((__u64)rb->host_mirror + ((__u64)host - (__u64)rb->host)); > > This is gross :-( > I hate this C miss-feature. > > What about: > return (char *)rb->host_mirror + (char*)host - (char*)rb->host; This was a generic suggestion. But after looking at ramblock.h and realizing that rb->host is not void*. return (uint8_t *)rb->host_mirror + (uint8_t *)host - rb->host; Sorry for looking too late. BTW, once here, why is the type of host_mirror different than the one from host? I don't know what is more confusing anymore. Later, Juan.
diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c index 8a2259581e..c4bd338e22 100644 --- a/migration/postcopy-ram.c +++ b/migration/postcopy-ram.c @@ -1350,6 +1350,43 @@ int postcopy_notify_shared_wake(RAMBlock *rb, uint64_t offset) return 0; } +/* Returns the mirror_host addr for a specific host address in ramblock */ +static inline void *migration_ram_get_mirror_addr(RAMBlock *rb, void *host) +{ + return (void *)((__u64)rb->host_mirror + ((__u64)host - (__u64)rb->host)); +} + +static int +qemu_uffd_continue(MigrationIncomingState *mis, RAMBlock *rb, void *host, + void *from) +{ + void *mirror_addr = migration_ram_get_mirror_addr(rb, host); + /* Doublemap uses small host page size */ + uint64_t psize = qemu_real_host_page_size(); + struct uffdio_continue req; + + /* + * Copy data first into the mirror host pointer; we can't directly copy + * data into rb->host because otherwise our thread will get trapped too. + */ + memcpy(mirror_addr, from, psize); + + /* Kick off the faluted threads to fetch data from the page cache */ + req.range.start = (__u64)host; + req.range.len = psize; + req.mode = 0; + if (ioctl(mis->userfault_fd, UFFDIO_CONTINUE, &req)) { + error_report("%s: UFFDIO_CONTINUE failed for start=%p" + " len=0x%"PRIx64": %s\n", __func__, host, + psize, strerror(-req.mapped)); + return req.mapped; + } + + postcopy_mark_received(mis, rb, host, psize / qemu_target_page_size()); + + return 0; +} + /* * Place a host page (from) at (host) atomically * returns 0 on success @@ -1359,6 +1396,18 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, { size_t pagesize = migration_ram_pagesize(rb); + trace_postcopy_place_page(rb->idstr, (uint8_t *)host - rb->host, host); + + if (postcopy_use_minor_fault(rb)) { + /* + * If minor fault used, we use UFFDIO_CONTINUE instead. + * + * TODO: support shared uffds (e.g. vhost-user). Currently we're + * skipping them. + */ + return qemu_uffd_continue(mis, rb, host, from); + } + /* copy also acks to the kernel waking the stalled thread up * TODO: We can inhibit that ack and only do it if it was requested * which would be slightly cheaper, but we'd have to be careful @@ -1372,7 +1421,6 @@ int postcopy_place_page(MigrationIncomingState *mis, void *host, void *from, return -e; } - trace_postcopy_place_page(host); return postcopy_notify_shared_wake(rb, qemu_ram_block_host_offset(rb, host)); } @@ -1385,10 +1433,13 @@ int postcopy_place_page_zero(MigrationIncomingState *mis, void *host, RAMBlock *rb) { size_t pagesize = migration_ram_pagesize(rb); - trace_postcopy_place_page_zero(host); + trace_postcopy_place_page_zero(rb->idstr, (uint8_t *)host - rb->host, host); /* Normal RAMBlocks can zero a page using UFFDIO_ZEROPAGE * but it's not available for everything (e.g. hugetlbpages) + * + * NOTE: when hugetlb double-map enabled, then this ramblock will never + * have RAM_UF_ZEROPAGE, so it'll always go to postcopy_place_page(). */ if (qemu_ram_is_uf_zeroable(rb)) { if (qemu_ufd_copy_ioctl(mis, host, NULL, pagesize, rb)) { diff --git a/migration/trace-events b/migration/trace-events index 6b418a0e9e..7baf235d22 100644 --- a/migration/trace-events +++ b/migration/trace-events @@ -265,8 +265,8 @@ postcopy_discard_send_range(const char *ramblock, unsigned long start, unsigned postcopy_cleanup_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" postcopy_init_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" postcopy_nhp_range(const char *ramblock, void *host_addr, size_t offset, size_t length) "%s: %p offset=0x%zx length=0x%zx" -postcopy_place_page(void *host_addr) "host=%p" -postcopy_place_page_zero(void *host_addr) "host=%p" +postcopy_place_page(const char *id, size_t offset, void *host_addr) "id=%s offset=0x%zx host=%p" +postcopy_place_page_zero(const char *id, size_t offset, void *host_addr) "id=%s offset=0x%zx host=%p" postcopy_ram_enable_notify(void) "" mark_postcopy_blocktime_begin(uint64_t addr, void *dd, uint32_t time, int cpu, int received) "addr: 0x%" PRIx64 ", dd: %p, time: %u, cpu: %d, already_received: %d" mark_postcopy_blocktime_end(uint64_t addr, void *dd, uint32_t time, int affected_cpu) "addr: 0x%" PRIx64 ", dd: %p, time: %u, affected_cpu: %d"
Teach QEMU to be able to handle page faults using UFFDIO_CONTINUE for hugetlbfs double mapped ranges. To copy the data, we need to use the mirror buffer created per ramblock by a raw memcpy(), then we can kick the faulted threads using UFFDIO_CONTINUE by installing the pgtables. Move trace_postcopy_place_page(host) upper so that it'll dump something for either UFFDIO_COPY or UFFDIO_CONTINUE. Signed-off-by: Peter Xu <peterx@redhat.com> --- migration/postcopy-ram.c | 55 ++++++++++++++++++++++++++++++++++++++-- migration/trace-events | 4 +-- 2 files changed, 55 insertions(+), 4 deletions(-)