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Message-ID: <1426030609.25026.88.camel@redhat.com>
Date: Tue, 10 Mar 2015 17:36:49 -0600
From: Alex Williamson <alex.williamson@...hat.com>
To: Alexey Kardashevskiy <aik@...abs.ru>
Cc: linuxppc-dev@...ts.ozlabs.org,
Benjamin Herrenschmidt <benh@...nel.crashing.org>,
Paul Mackerras <paulus@...ba.org>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 07/29] vfio: powerpc/spapr: Moving pinning/unpinning
to helpers
On Tue, 2015-03-10 at 01:07 +1100, 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.
>
> Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
> ---
> drivers/vfio/vfio_iommu_spapr_tce.c | 70 ++++++++++++++++++++++++++++---------
> 1 file changed, 54 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/vfio/vfio_iommu_spapr_tce.c b/drivers/vfio/vfio_iommu_spapr_tce.c
> index d3ab34f..ca396e5 100644
> --- a/drivers/vfio/vfio_iommu_spapr_tce.c
> +++ b/drivers/vfio/vfio_iommu_spapr_tce.c
> @@ -204,7 +204,6 @@ static void tce_iommu_release(void *iommu_data)
> struct iommu_table *tbl = container->tbl;
>
> WARN_ON(tbl && !tbl->it_group);
> - tce_iommu_disable(container);
>
> if (tbl) {
> tce_iommu_clear(container, tbl, tbl->it_offset, tbl->it_size);
> @@ -212,63 +211,102 @@ static void tce_iommu_release(void *iommu_data)
> if (tbl->it_group)
> tce_iommu_detach_group(iommu_data, 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;
> +
> + /*
> + * VFIO cannot map/unmap when a container is not enabled so
> + * we would not need this check but KVM could map/unmap and if
> + * this happened, we must not put pages as KVM does not get them as
> + * it expects memory pre-registation to do this part.
> + */
> + if (!container->enabled)
> + return;
> +
> + page = pfn_to_page(__pa(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, (unsigned long) __va(oldtce));
> }
>
> return 0;
> }
>
> +static unsigned long tce_get_hva(struct tce_container *container,
> + unsigned page_shift, unsigned long tce)
> +{
> + long ret;
> + struct page *page = NULL;
> + unsigned long hva;
> + enum dma_data_direction direction = iommu_tce_direction(tce);
> +
> + ret = get_user_pages_fast(tce & PAGE_MASK, 1,
> + direction != DMA_TO_DEVICE, &page);
> + if (unlikely(ret != 1))
> + return -1;
> +
> + hva = (unsigned long) page_address(page);
> +
> + return hva;
> +}
It's a bit crude to return -1 for an unsigned long function. You might
want to later think about cleaning this up to return int with a proper
error code and return hva via a pointer. We don't really need to store
'ret' here either.
> +
> 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;
> + struct page *page;
> unsigned long hva;
> enum dma_data_direction direction = iommu_tce_direction(tce);
>
> for (i = 0; i < pages; ++i) {
> - ret = get_user_pages_fast(tce & PAGE_MASK, 1,
> - direction != DMA_TO_DEVICE, &page);
> - if (unlikely(ret != 1)) {
> + hva = tce_get_hva(container, tbl->it_page_shift, tce);
> + if (hva == -1) {
> ret = -EFAULT;
> break;
> }
>
> + page = pfn_to_page(__pa(hva) >> PAGE_SHIFT);
> if (!tce_page_is_contained(page, tbl->it_page_shift)) {
> ret = -EPERM;
> break;
> }
>
> - hva = (unsigned long) page_address(page) +
> - (tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK);
> + /* Preserve offset within IOMMU page */
> + hva |= tce & IOMMU_PAGE_MASK(tbl) & ~PAGE_MASK;
>
> ret = iommu_tce_build(tbl, entry + i, hva, direction);
> if (ret) {
> - put_page(page);
> + tce_iommu_unuse_page(container, hva);
> pr_err("iommu_tce: %s failed ioba=%lx, tce=%lx, ret=%ld\n",
> __func__, entry << tbl->it_page_shift,
> tce, ret);
--
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