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SubjectRe: [PATCH kernel v10 11/34] vfio: powerpc/spapr: Moving pinning/unpinning to helpers
On Tue, May 12, 2015 at 01:39:00AM +1000, Alexey Kardashevskiy wrote:
>This is a pretty mechanical patch to make next patches simpler.
>
>New tce_iommu_unuse_page() helper does put_page() now but it might skip
>that after the memory registering patch applied.
>
>As we are here, this removes unnecessary checks for a value returned
>by pfn_to_page() as it cannot possibly return NULL.
>
>This moves tce_iommu_disable() later to let tce_iommu_clear() know if
>the container has been enabled because if it has not been, then
>put_page() must not be called on TCEs from the TCE table. This situation
>is not yet possible but it will after KVM acceleration patchset is
>applied.
>
>This changes code to work with physical addresses rather than linear
>mapping addresses for better code readability. Following patches will
>add an xchg() callback for an IOMMU table which will accept/return
>physical addresses (unlike current tce_build()) which will eliminate
>redundant conversions.
>
>Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
>[aw: for the vfio related changes]
>Acked-by: Alex Williamson <alex.williamson@redhat.com>
>Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

Reviewed-by: Gavin Shan <gwshan@linux.vnet.ibm.com>

>---
>Changes:
>v9:
>* changed helpers to work with physical addresses rather than linear
>(for simplicity - later ::xchg() will receive physical and avoid
>additional convertions)
>
>v6:
>* tce_get_hva() returns hva via a pointer
>---
> drivers/vfio/vfio_iommu_spapr_tce.c | 61 +++++++++++++++++++++++++------------
> 1 file changed, 41 insertions(+), 20 deletions(-)
>
>diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
>index e21479c..115d5e6 100644
>--- a/drivers/vfio/vfio_iommu_spapr_tce.c
>+++ b/drivers/vfio/vfio_iommu_spapr_tce.c
>@@ -191,69 +191,90 @@ static void tce_iommu_release(void *iommu_data)
> struct tce_container *container = iommu_data;
>
> WARN_ON(container->tbl && !container->tbl->it_group);
>- tce_iommu_disable(container);
>
> if (container->tbl && container->tbl->it_group)
> tce_iommu_detach_group(iommu_data, container->tbl->it_group);
>
>+ tce_iommu_disable(container);
> mutex_destroy(&container->lock);
>
> kfree(container);
> }
>
>+static void tce_iommu_unuse_page(struct tce_container *container,
>+ unsigned long oldtce)
>+{
>+ struct page *page;
>+
>+ if (!(oldtce & (TCE_PCI_READ | TCE_PCI_WRITE)))
>+ return;
>+

It might be worthy to have a global helper function in iommu.h to check
if the given TCE entry is empty or not, for better readability. I would
think the helper function is used here and there :-)

Thanks,
Gavin

>+ page = pfn_to_page(oldtce >> PAGE_SHIFT);
>+
>+ if (oldtce & TCE_PCI_WRITE)
>+ SetPageDirty(page);
>+
>+ put_page(page);
>+}
>+
> static int tce_iommu_clear(struct tce_container *container,
> struct iommu_table *tbl,
> unsigned long entry, unsigned long pages)
> {
> unsigned long oldtce;
>- struct page *page;
>
> for ( ; pages; --pages, ++entry) {
> oldtce = iommu_clear_tce(tbl, entry);
> if (!oldtce)
> continue;
>
>- page = pfn_to_page(oldtce >> PAGE_SHIFT);
>- WARN_ON(!page);
>- if (page) {
>- if (oldtce & TCE_PCI_WRITE)
>- SetPageDirty(page);
>- put_page(page);
>- }
>+ tce_iommu_unuse_page(container, oldtce);
> }
>
> return 0;
> }
>
>+static int tce_iommu_use_page(unsigned long tce, unsigned long *hpa)
>+{
>+ struct page *page = NULL;
>+ enum dma_data_direction direction = iommu_tce_direction(tce);
>+
>+ if (get_user_pages_fast(tce & PAGE_MASK, 1,
>+ direction != DMA_TO_DEVICE, &page) != 1)
>+ return -EFAULT;
>+
>+ *hpa = __pa((unsigned long) page_address(page));
>+
>+ return 0;
>+}
>+
> static long tce_iommu_build(struct tce_container *container,
> struct iommu_table *tbl,
> unsigned long entry, unsigned long tce, unsigned long pages)
> {
> long i, ret = 0;
>- struct page *page = NULL;
>- unsigned long hva;
>+ struct page *page;
>+ unsigned long hpa;
> enum dma_data_direction direction = iommu_tce_direction(tce);
>
> for (i = 0; i < pages; ++i) {
> unsigned long offset = tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK;
>
>- ret = get_user_pages_fast(tce & PAGE_MASK, 1,
>- direction != DMA_TO_DEVICE, &page);
>- if (unlikely(ret != 1)) {
>- ret = -EFAULT;
>+ ret = tce_iommu_use_page(tce, &hpa);
>+ if (ret)
> break;
>- }
>
>+ page = pfn_to_page(hpa >> PAGE_SHIFT);
> if (!tce_page_is_contained(page, tbl->it_page_shift)) {
> ret = -EPERM;
> break;
> }
>
>- hva = (unsigned long) page_address(page) + offset;
>-
>- ret = iommu_tce_build(tbl, entry + i, hva, direction);
>+ hpa |= offset;
>+ ret = iommu_tce_build(tbl, entry + i, (unsigned long) __va(hpa),
>+ direction);
> if (ret) {
>- put_page(page);
>+ tce_iommu_unuse_page(container, hpa);
> pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx, ret=%ld\n",
> __func__, entry << tbl->it_page_shift,
> tce, ret);
>--
>2.4.0.rc3.8.gfb3e7d5
>



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