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    SubjectRe: [PATCH 19/34] AMD IOMMU: add functions to send IOMMU commands
    On Thu, 26 Jun 2008 21:27:55 +0200 Joerg Roedel <joerg.roedel@amd.com> wrote:

    > This patch adds generic handling function as well as all functions to send
    > specific commands to the IOMMU hardware as required by this driver.
    >
    > Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
    > ---
    > arch/x86/kernel/amd_iommu.c | 106 +++++++++++++++++++++++++++++++++++++++++++
    > 1 files changed, 106 insertions(+), 0 deletions(-)
    >
    > diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
    > index 90392c7..a24ee4a 100644
    > --- a/arch/x86/kernel/amd_iommu.c
    > +++ b/arch/x86/kernel/amd_iommu.c
    > @@ -37,4 +37,110 @@ struct command {
    > u32 data[4];
    > };
    >
    > +static int __iommu_queue_command(struct amd_iommu *iommu, struct command *cmd)
    > +{
    > + u32 tail, head;
    > + u8 *target;
    > +
    > + tail = readl(iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
    > + target = (iommu->cmd_buf + tail);
    > + memcpy_toio(target, cmd, sizeof(*cmd));
    > + tail = (tail + sizeof(*cmd)) % iommu->cmd_buf_size;
    > + head = readl(iommu->mmio_base + MMIO_CMD_HEAD_OFFSET);
    > + if (tail == head)
    > + return -ENOMEM;
    > + writel(tail, iommu->mmio_base + MMIO_CMD_TAIL_OFFSET);
    > +
    > + return 0;
    > +}
    > +
    > +static int iommu_queue_command(struct amd_iommu *iommu, struct command *cmd)
    > +{
    > + unsigned long flags;
    > + int ret;
    > +
    > + spin_lock_irqsave(&iommu->lock, flags);
    > + ret = __iommu_queue_command(iommu, cmd);
    > + spin_unlock_irqrestore(&iommu->lock, flags);
    > +
    > + return ret;
    > +}
    > +
    > +static int iommu_completion_wait(struct amd_iommu *iommu)
    > +{
    > + int ret;
    > + struct command cmd;
    > + volatile u64 ready = 0;
    > + unsigned long ready_phys = virt_to_phys(&ready);
    > +
    > + memset(&cmd, 0, sizeof(cmd));
    > + cmd.data[0] = LOW_U32(ready_phys) | CMD_COMPL_WAIT_STORE_MASK;
    > + cmd.data[1] = HIGH_U32(ready_phys);
    > + cmd.data[2] = 1; /* value written to 'ready' */
    > + CMD_SET_TYPE(&cmd, CMD_COMPL_WAIT);
    > +
    > + iommu->need_sync = 0;
    > +
    > + ret = iommu_queue_command(iommu, &cmd);
    > +
    > + if (ret)
    > + return ret;
    > +
    > + while (!ready)
    > + cpu_relax();

    I busywait is a big red flag. An uncommented one is not acceptable IMO.

    What is the maximum duration?

    Is it not possible to sleep and await an interrupt?

    Should we implement a timeout in case the hardware is busted?

    > + return 0;
    > +}
    > +
    > +static int iommu_queue_inv_dev_entry(struct amd_iommu *iommu, u16 devid)
    > +{
    > + struct command cmd;

    `command' was a poorly-chosen identifier for this structure. Too generic.

    > + BUG_ON(iommu == NULL);
    > +
    > + memset(&cmd, 0, sizeof(cmd));
    > + CMD_SET_TYPE(&cmd, CMD_INV_DEV_ENTRY);
    > + cmd.data[0] = devid;
    > +
    > + iommu->need_sync = 1;
    > +
    > + return iommu_queue_command(iommu, &cmd);
    > +}
    > +
    > +static int iommu_queue_inv_iommu_pages(struct amd_iommu *iommu,
    > + u64 address, u16 domid, int pde, int s)
    > +{
    > + struct command cmd;
    > +
    > + memset(&cmd, 0, sizeof(cmd));
    > + address &= PAGE_MASK;
    > + CMD_SET_TYPE(&cmd, CMD_INV_IOMMU_PAGES);
    > + cmd.data[1] |= domid;
    > + cmd.data[2] = LOW_U32(address);
    > + cmd.data[3] = HIGH_U32(address);
    > + if (s)
    > + cmd.data[2] |= CMD_INV_IOMMU_PAGES_SIZE_MASK;
    > + if (pde)
    > + cmd.data[2] |= CMD_INV_IOMMU_PAGES_PDE_MASK;
    > +
    > + iommu->need_sync = 1;
    > +
    > + return iommu_queue_command(iommu, &cmd);
    > +}
    > +
    > +static int iommu_flush_pages(struct amd_iommu *iommu, u16 domid,
    > + u64 address, size_t size)
    > +{
    > + int i;
    > + unsigned pages = to_pages(address, size);
    > +
    > + address &= PAGE_MASK;
    > +
    > + for (i = 0; i < pages; ++i) {
    > + iommu_queue_inv_iommu_pages(iommu, address, domid, 0, 0);
    > + address += PAGE_SIZE;
    > + }
    > +
    > + return 0;
    > +}



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