Messages in this thread | | | Date | Wed, 30 Oct 2019 10:20:14 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH] iommu/amd: Do not re-fetch iommu->cmd_buf_tail |
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On Thu, Oct 24, 2019 at 02:54:10PM +0200, Denys Vlasenko wrote: > 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> > --- > drivers/iommu/amd_iommu.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-)
Applied, thanks.
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