diff options
| author | Denys Vlasenko <dvlasenk@redhat.com> | 2019-10-24 14:54:10 +0200 |
|---|---|---|
| committer | Joerg Roedel <jroedel@suse.de> | 2019-10-30 10:19:49 +0100 |
| commit | a5bbbf37c6f8522a1afd46c37b5a0d1ce63232b7 (patch) | |
| tree | 48db3a030d7c413cfbd5c48d73abc70e6f7f34da /drivers/iommu | |
| parent | 3057fb9377eb5e73386dd0d8804bf72bdd23e391 (diff) | |
iommu/amd: Do not re-fetch iommu->cmd_buf_tail
The compiler is not smart enough to realize that iommu->cmd_buf_tail
can't be modified across memcpy:
41 8b 45 74 mov 0x74(%r13),%eax # iommu->cmd_buf_tail
44 8d 78 10 lea 0x10(%rax),%r15d # += sizeof(*cmd)
41 81 e7 ff 1f 00 00 and $0x1fff,%r15d # %= CMD_BUFFER_SIZE
49 03 45 68 add 0x68(%r13),%rax # target = iommu->cmd_buf + iommu->cmd_buf_tail
45 89 7d 74 mov %r15d,0x74(%r13) # store to iommu->cmd_buf_tail
49 8b 34 24 mov (%r12),%rsi # memcpy
49 8b 7c 24 08 mov 0x8(%r12),%rdi # memcpy
48 89 30 mov %rsi,(%rax) # memcpy
48 89 78 08 mov %rdi,0x8(%rax) # memcpy
49 8b 55 38 mov 0x38(%r13),%rdx # iommu->mmio_base
41 8b 45 74 mov 0x74(%r13),%eax # redundant load of iommu->cmd_buf_tail
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
89 82 08 20 00 00 mov %eax,0x2008(%rdx) # writel
CC: Tom Lendacky <thomas.lendacky@amd.com>
CC: Joerg Roedel <jroedel@suse.de>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Diffstat (limited to 'drivers/iommu')
| -rw-r--r-- | drivers/iommu/amd_iommu.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c index fb54df5c2e11..69458d309be0 100644 --- a/drivers/iommu/amd_iommu.c +++ b/drivers/iommu/amd_iommu.c @@ -852,17 +852,18 @@ static void copy_cmd_to_buffer(struct amd_iommu *iommu, struct iommu_cmd *cmd) { u8 *target; - - target = iommu->cmd_buf + iommu->cmd_buf_tail; - - iommu->cmd_buf_tail += sizeof(*cmd); - iommu->cmd_buf_tail %= CMD_BUFFER_SIZE; + u32 tail; /* Copy command to buffer */ + tail = iommu->cmd_buf_tail; + target = iommu->cmd_buf + tail; memcpy(target, cmd, sizeof(*cmd)); + tail = (tail + sizeof(*cmd)) % CMD_BUFFER_SIZE; + iommu->cmd_buf_tail = tail; + /* Tell the IOMMU about it */ - writel(iommu->cmd_buf_tail, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET); + writel(tail, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET); } static void build_completion_wait(struct iommu_cmd *cmd, u64 address) |