From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52531) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1chJ4c-00057P-94 for qemu-devel@nongnu.org; Fri, 24 Feb 2017 11:50:27 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1chJ4Y-0005XP-7p for qemu-devel@nongnu.org; Fri, 24 Feb 2017 11:50:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:59580) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1chJ4X-0005Wr-Uq for qemu-devel@nongnu.org; Fri, 24 Feb 2017 11:50:22 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 0EA4B80462 for ; Fri, 24 Feb 2017 16:50:22 +0000 (UTC) Date: Fri, 24 Feb 2017 16:50:17 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20170224165016.GO8830@work-vm> References: <20170206173306.20603-1-dgilbert@redhat.com> <20170206173306.20603-5-dgilbert@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Subject: Re: [Qemu-devel] [PATCH v2 04/16] exec: ram_block_discard_range List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Laurent Vivier Cc: qemu-devel@nongnu.org, quintela@redhat.com, aarcange@redhat.com * Laurent Vivier (lvivier@redhat.com) wrote: > On 06/02/2017 18:32, Dr. David Alan Gilbert (git) wrote: > > From: "Dr. David Alan Gilbert" > > > > Create ram_block_discard_range in exec.c to replace > > postcopy_ram_discard_range and most of ram_discard_range. > > > > Those two routines are a bit of a weird combination, and > > ram_discard_range is about to get more complex for hugepages. > > It's OS dependent code (so shouldn't be in migration/ram.c) but > > it needs quite a bit of the innards of RAMBlock so doesn't belong in > > the os*.c. > > > > Signed-off-by: Dr. David Alan Gilbert > > --- > > exec.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++ > > include/exec/cpu-common.h | 1 + > > 2 files changed, 60 insertions(+) > > > > diff --git a/exec.c b/exec.c > > index 8b9ed73..e040cdf 100644 > > --- a/exec.c > > +++ b/exec.c > > @@ -45,6 +45,12 @@ > > #include "exec/address-spaces.h" > > #include "sysemu/xen-mapcache.h" > > #include "trace-root.h" > > + > > +#ifdef CONFIG_FALLOCATE_PUNCH_HOLE > > +#include > > +#include > > +#endif > > + > > #endif > > #include "exec/cpu-all.h" > > #include "qemu/rcu_queue.h" > > @@ -3286,4 +3292,57 @@ int qemu_ram_foreach_block(RAMBlockIterFunc func, void *opaque) > > rcu_read_unlock(); > > return ret; > > } > > + > > +/* > > + * Unmap pages of memory from start to start+length such that > > + * they a) read as 0, b) Trigger whatever fault mechanism > > + * the OS provides for postcopy. > > + * The pages must be unmapped by the end of the function. > > + * Returns: 0 on success, none-0 on failure > > + * > > + */ > > +int ram_block_discard_range(RAMBlock *rb, uint64_t start, size_t length) > > +{ > > + int ret = -1; > > + > > + rcu_read_lock(); > > + uint8_t *host_startaddr = rb->host + start; > > + > > + if ((uintptr_t)host_startaddr & (rb->page_size - 1)) { > > + error_report("ram_block_discard_range: Unaligned start address: %p", > > + host_startaddr); > > + goto err; > > + } > > + > > + if ((start + length) <= rb->used_length) { > > + uint8_t *host_endaddr = host_startaddr + length; > > + if ((uintptr_t)host_endaddr & (rb->page_size - 1)) { > > + error_report("ram_block_discard_range: Unaligned end address: %p", > > + host_endaddr); > > + goto err; > > + } > > + > > + errno = ENOTSUP; /* If we are missing MADVISE etc */ > > + > > +#if defined(CONFIG_MADVISE) > > + ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED); > > +#endif > > + if (ret) { > > + ret = -errno; > > + error_report("ram_block_discard_range: Failed to discard range " > > + "%s:%" PRIx64 " +%zx (%d)", > > + rb->idstr, start, length, ret); > > + } > > + } else { > > + error_report("ram_block_discard_range: Overrun block '%s' (%" PRIu64 > > + "/%zx/" RAM_ADDR_FMT")", > > + rb->idstr, start, length, rb->used_length); > > + } > > + > > +err: > > + rcu_read_unlock(); > > + > > + return ret; > > +} > > I really looks like a copy'n'paste from ram_discard_range(). It could be > clearer if you remove the code from ram_discard_range() and call this > function instead. Yes, flattened into the latter commit. > I think you don't need the "#if defined(CONFIG_MADVISE)" as you use > qemu_madvise() (or you should use madvise() directly if you want to > avoid the posix_madvise()). Yes, changed to CONFIG_MADVISE + madvise() I need to avoid posix_madvise because it doesn't do the same thing. > [perhaps qemu_madvise() should set errno to ENOTSUP instead of EINVAL] The difficulty is with how it fiddles with it's QEMU_MADV_* macros, when it finds one that doesn't exist it gets defined as -1 or the like which then fails that way. Dave > > Laurent -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK