75 lines
2.4 KiB
Diff
75 lines
2.4 KiB
Diff
From 851ffb4eea917e2708c912291dea4d133026c0ac Mon Sep 17 00:00:00 2001
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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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Date: Fri, 20 Nov 2015 12:16:02 -0500
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Subject: [PATCH 2/3] blktap2: Use RING_COPY_REQUEST
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Instead of RING_GET_REQUEST. Using a local copy of the
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ring (and also with proper memory barriers) will mean
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we can do not have to worry about the compiler optimizing
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the code and doing a double-fetch in the shared memory space.
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This is part of XSA155.
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Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
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---
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v2: Fix compile issues with tapdisk-vbd
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---
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tools/blktap2/drivers/block-log.c | 3 ++-
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tools/blktap2/drivers/tapdisk-vbd.c | 8 ++++----
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2 files changed, 6 insertions(+), 5 deletions(-)
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diff --git a/tools/blktap2/drivers/block-log.c b/tools/blktap2/drivers/block-log.c
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index 5330cdc..5f3bd35 100644
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--- a/tools/blktap2/drivers/block-log.c
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+++ b/tools/blktap2/drivers/block-log.c
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@@ -494,11 +494,12 @@ static int ctl_kick(struct tdlog_state* s, int fd)
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reqstart = s->bring.req_cons;
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reqend = s->sring->req_prod;
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+ xen_mb();
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BDPRINTF("ctl: ring kicked (start = %u, end = %u)", reqstart, reqend);
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while (reqstart != reqend) {
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/* XXX actually submit these! */
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- memcpy(&req, RING_GET_REQUEST(&s->bring, reqstart), sizeof(req));
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+ RING_COPY_REQUEST(&s->bring, reqstart, &req);
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BDPRINTF("ctl: read request %"PRIu64":%u", req.sector, req.count);
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s->bring.req_cons = ++reqstart;
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diff --git a/tools/blktap2/drivers/tapdisk-vbd.c b/tools/blktap2/drivers/tapdisk-vbd.c
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index 6d1d94a..89ef9ed 100644
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--- a/tools/blktap2/drivers/tapdisk-vbd.c
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+++ b/tools/blktap2/drivers/tapdisk-vbd.c
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@@ -1555,7 +1555,7 @@ tapdisk_vbd_pull_ring_requests(td_vbd_t *vbd)
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int idx;
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RING_IDX rp, rc;
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td_ring_t *ring;
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- blkif_request_t *req;
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+ blkif_request_t req;
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td_vbd_request_t *vreq;
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ring = &vbd->ring;
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@@ -1566,16 +1566,16 @@ tapdisk_vbd_pull_ring_requests(td_vbd_t *vbd)
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xen_rmb();
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for (rc = ring->fe_ring.req_cons; rc != rp; rc++) {
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- req = RING_GET_REQUEST(&ring->fe_ring, rc);
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+ RING_COPY_REQUEST(&ring->fe_ring, rc, &req);
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++ring->fe_ring.req_cons;
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- idx = req->id;
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+ idx = req.id;
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vreq = &vbd->request_list[idx];
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ASSERT(list_empty(&vreq->next));
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ASSERT(vreq->secs_pending == 0);
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- memcpy(&vreq->req, req, sizeof(blkif_request_t));
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+ memcpy(&vreq->req, &req, sizeof(blkif_request_t));
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vbd->received++;
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vreq->vbd = vbd;
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--
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2.1.4
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