From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48667) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XqK1R-0004xq-3S for qemu-devel@nongnu.org; Mon, 17 Nov 2014 05:59:11 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XqK1K-0007W2-Va for qemu-devel@nongnu.org; Mon, 17 Nov 2014 05:59:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42232) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XqK1K-0007Vr-PB for qemu-devel@nongnu.org; Mon, 17 Nov 2014 05:58:58 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id sAHAwvRK023820 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Mon, 17 Nov 2014 05:58:57 -0500 Date: Mon, 17 Nov 2014 10:58:53 +0000 From: "Dr. David Alan Gilbert" Message-ID: <20141117105852.GC2237@work-vm> References: <1415785203-26938-1-git-send-email-mst@redhat.com> <1415785203-26938-3-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415785203-26938-3-git-send-email-mst@redhat.com> Subject: Re: [Qemu-devel] [PATCH 2/4] exec: add wrapper for host pointer access List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Michael S. Tsirkin" Cc: Paolo Bonzini , quintela@redhat.com, qemu-devel@nongnu.org, dgilbert@redhat.com * Michael S. Tsirkin (mst@redhat.com) wrote: > host pointer accesses force pointer math, let's > add a wrapper to make them safer. > > Signed-off-by: Michael S. Tsirkin > --- > include/exec/cpu-all.h | 5 +++++ > exec.c | 10 +++++----- > 2 files changed, 10 insertions(+), 5 deletions(-) > > diff --git a/include/exec/cpu-all.h b/include/exec/cpu-all.h > index c085804..9d8d408 100644 > --- a/include/exec/cpu-all.h > +++ b/include/exec/cpu-all.h > @@ -313,6 +313,11 @@ typedef struct RAMBlock { > int fd; > } RAMBlock; > > +static inline void *ramblock_ptr(RAMBlock *block, ram_addr_t offset) > +{ > + return (char *)block->host + offset; > +} I'm a bit surprised you don't need to pass a length to this to be able to tell how much you can access. > typedef struct RAMList { > QemuMutex mutex; > /* Protected by the iothread lock. */ > diff --git a/exec.c b/exec.c > index ad5cf12..9648669 100644 > --- a/exec.c > +++ b/exec.c > @@ -840,7 +840,7 @@ static void tlb_reset_dirty_range_all(ram_addr_t start, ram_addr_t length) > > block = qemu_get_ram_block(start); > assert(block == qemu_get_ram_block(end - 1)); > - start1 = (uintptr_t)block->host + (start - block->offset); > + start1 = (uintptr_t)ramblock_ptr(block, start - block->offset); > cpu_tlb_reset_dirty_all(start1, length); > } > > @@ -1500,7 +1500,7 @@ void qemu_ram_remap(ram_addr_t addr, ram_addr_t length) > QTAILQ_FOREACH(block, &ram_list.blocks, next) { > offset = addr - block->offset; > if (offset < block->length) { > - vaddr = block->host + offset; > + vaddr = ramblock_ptr(block, offset); > if (block->flags & RAM_PREALLOC) { > ; > } else if (xen_enabled()) { > @@ -1551,7 +1551,7 @@ void *qemu_get_ram_block_host_ptr(ram_addr_t addr) > { > RAMBlock *block = qemu_get_ram_block(addr); > > - return block->host; > + return ramblock_ptr(block, 0); > } > > /* Return a host pointer to ram allocated with qemu_ram_alloc. > @@ -1578,7 +1578,7 @@ void *qemu_get_ram_ptr(ram_addr_t addr) > xen_map_cache(block->offset, block->length, 1); > } > } > - return block->host + (addr - block->offset); > + return ramblock_ptr(block, addr - block->offset); > } which then makes me wonder if all the uses of this are safe near the end of the block. > /* Return a host pointer to guest's ram. Similar to qemu_get_ram_ptr > @@ -1597,7 +1597,7 @@ static void *qemu_ram_ptr_length(ram_addr_t addr, hwaddr *size) > if (addr - block->offset < block->length) { > if (addr - block->offset + *size > block->length) > *size = block->length - addr + block->offset; > - return block->host + (addr - block->offset); > + return ramblock_ptr(block, addr - block->offset); > } but then this sounds like it's going to have partial duplication, it already looks like it's only going to succeed if it finds itself a block that the access fits in. Dave > } > > -- > MST > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK