From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57720) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VbX1e-0001no-Mk for qemu-devel@nongnu.org; Wed, 30 Oct 2013 10:45:44 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VbX1Y-0003IN-I9 for qemu-devel@nongnu.org; Wed, 30 Oct 2013 10:45:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:63170) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VbX1Y-0003IJ-7U for qemu-devel@nongnu.org; Wed, 30 Oct 2013 10:45:32 -0400 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 r9UEjVfG029327 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Wed, 30 Oct 2013 10:45:31 -0400 From: Jeff Cody Date: Wed, 30 Oct 2013 10:44:49 -0400 Message-Id: <0f93424a1d29f6716f6de70ce975e6602d866cf5.1383143104.git.jcody@redhat.com> In-Reply-To: References: In-Reply-To: References: Subject: [Qemu-devel] [PATCH v8 12/19] block: vhdx - remove BAT file offset bit shifting List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: kwolf@redhat.com, stefanha@redhat.com Bit shifting can be fun, but in this case it was unnecessary. The upper 44 bits of the 64-bit BAT entry is specifies the File Offset, so we shifted the bits to get access to the value. However, per the spec the value is in MB. So we dutifully shifted back to the left by 20 bits, to convert to a true uint64_t file offset. This replaces those steps with just a bit mask, to get rid of the lower 20 bits instead. Signed-off-by: Jeff Cody --- block/vhdx.c | 6 ++---- block/vhdx.h | 1 - 2 files changed, 2 insertions(+), 5 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index 050f071..158edab 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -985,7 +985,7 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num, sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits; - sinfo->file_offset = s->bat[sinfo->bat_idx] >> VHDX_BAT_FILE_OFF_BITS; + sinfo->file_offset = s->bat[sinfo->bat_idx] & VHDX_BAT_FILE_OFF_MASK; sinfo->block_offset = block_offset << s->logical_sector_size_bits; @@ -999,7 +999,6 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num, * in the block, and add in the payload data block offset * in the file, in bytes, to get the final read address */ - sinfo->file_offset <<= 20; /* now in bytes, rather than 1MB units */ sinfo->file_offset += sinfo->block_offset; } @@ -1098,8 +1097,7 @@ static void vhdx_update_bat_table_entry(BlockDriverState *bs, BDRVVHDXState *s, { /* The BAT entry is a uint64, with 44 bits for the file offset in units of * 1MB, and 3 bits for the block state. */ - s->bat[sinfo->bat_idx] = ((sinfo->file_offset>>20) << - VHDX_BAT_FILE_OFF_BITS); + s->bat[sinfo->bat_idx] = sinfo->file_offset; s->bat[sinfo->bat_idx] |= state & VHDX_BAT_STATE_BIT_MASK; diff --git a/block/vhdx.h b/block/vhdx.h index f331548..d3598e0 100644 --- a/block/vhdx.h +++ b/block/vhdx.h @@ -229,7 +229,6 @@ typedef struct QEMU_PACKED VHDXLogDataSector { /* upper 44 bits are the file offset in 1MB units lower 3 bits are the state other bits are reserved */ #define VHDX_BAT_STATE_BIT_MASK 0x07 -#define VHDX_BAT_FILE_OFF_BITS (64 - 44) #define VHDX_BAT_FILE_OFF_MASK 0xFFFFFFFFFFF00000 /* upper 44 bits */ typedef uint64_t VHDXBatEntry; -- 1.8.3.1