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Date: Fri, 07 Oct 2022 08:59:27 +0200
From: Niklas Schnelle <schnelle@...ux.ibm.com>
To: Matthew Rosato <mjrosato@...ux.ibm.com>,
Pierre Morel <pmorel@...ux.ibm.com>, iommu@...ts.linux.dev
Cc: linux-s390@...r.kernel.org, borntraeger@...ux.ibm.com,
hca@...ux.ibm.com, gor@...ux.ibm.com,
gerald.schaefer@...ux.ibm.com, agordeev@...ux.ibm.com,
svens@...ux.ibm.com, joro@...tes.org, will@...nel.org,
robin.murphy@....com, jgg@...dia.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 6/6] iommu/s390: Implement map_pages()/unmap_pages()
instead of map()/unmap()
On Thu, 2022-10-06 at 17:03 -0400, Matthew Rosato wrote:
> On 10/6/22 10:47 AM, Niklas Schnelle wrote:
> > While s390-iommu currently implements the map_page()/unmap_page()
> > operations which only map/unmap a single page at a time the internal
> > s390_iommu_update_trans() API already supports mapping/unmapping a range
> > of pages at once. Take advantage of this by implementing the
> > map_pages()/unmap_pages() operations instead thus allowing users of the
> > IOMMU drivers to map multiple pages in a single call followed by
> > a single I/O TLB flush if needed.
> >
> > Signed-off-by: Niklas Schnelle <schnelle@...ux.ibm.com>
> > ---
> > drivers/iommu/s390-iommu.c | 48 +++++++++++++++++++++++++-------------
> > 1 file changed, 32 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/iommu/s390-iommu.c b/drivers/iommu/s390-iommu.c
> > index ac200f0b81fa..7b92855135ac 100644
> > --- a/drivers/iommu/s390-iommu.c
> > +++ b/drivers/iommu/s390-iommu.c
> > @@ -189,20 +189,15 @@ static void s390_iommu_release_device(struct device *dev)
> >
> > static int s390_iommu_update_trans(struct s390_domain *s390_domain,
> > phys_addr_t pa, dma_addr_t dma_addr,
> > - size_t size, int flags)
> > + unsigned long nr_pages, int flags)
> > {
> > phys_addr_t page_addr = pa & PAGE_MASK;
> > dma_addr_t start_dma_addr = dma_addr;
> > - unsigned long irq_flags, nr_pages, i;
> > + unsigned long irq_flags, i;
> > struct zpci_dev *zdev;
> > unsigned long *entry;
> > int rc = 0;
> >
> > - if (dma_addr < s390_domain->domain.geometry.aperture_start ||
> > - (dma_addr + size - 1) > s390_domain->domain.geometry.aperture_end)
> > - return -EINVAL;
> > -
> > - nr_pages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > if (!nr_pages)
> > return 0;
> >
> > @@ -245,11 +240,24 @@ static int s390_iommu_update_trans(struct s390_domain *s390_domain,
> > return rc;
> > }
> >
> > -static int s390_iommu_map(struct iommu_domain *domain, unsigned long iova,
> > - phys_addr_t paddr, size_t size, int prot, gfp_t gfp)
> > +static int s390_iommu_map_pages(struct iommu_domain *domain,
> > + unsigned long iova, phys_addr_t paddr,
> > + size_t pgsize, size_t pgcount,
> > + int prot, gfp_t gfp, size_t *mapped)
> > {
> > struct s390_domain *s390_domain = to_s390_domain(domain);
> > int flags = ZPCI_PTE_VALID, rc = 0;
> > + size_t size = pgcount << __ffs(pgsize);
> > +
> > + if (pgsize != SZ_4K)
> > + return -EINVAL;
> > +
> > + if (iova < s390_domain->domain.geometry.aperture_start ||
> > + (iova + size - 1) > s390_domain->domain.geometry.aperture_end)
> > + return -EINVAL;
> > +
> > + if (!IS_ALIGNED(iova | paddr, pgsize))
> > + return -EINVAL;
> >
> > if (!(prot & IOMMU_READ))
> > return -EINVAL;
> > @@ -258,7 +266,9 @@ static int s390_iommu_map(struct iommu_domain *domain, unsigned long iova,
> > flags |= ZPCI_TABLE_PROTECTED;
> >
> > rc = s390_iommu_update_trans(s390_domain, paddr, iova,
> > - size, flags);
> > + pgcount, flags);
> > + if (!rc)
> > + *mapped = size;
> >
> > return rc;
> > }
> > @@ -294,21 +304,27 @@ static phys_addr_t s390_iommu_iova_to_phys(struct iommu_domain *domain,
> > return phys;
> > }
> >
> > -static size_t s390_iommu_unmap(struct iommu_domain *domain,
> > - unsigned long iova, size_t size,
> > - struct iommu_iotlb_gather *gather)
> > +static size_t s390_iommu_unmap_pages(struct iommu_domain *domain,
> > + unsigned long iova,
> > + size_t pgsize, size_t pgcount,
> > + struct iommu_iotlb_gather *gather)
> > {
> > struct s390_domain *s390_domain = to_s390_domain(domain);
> > + size_t size = pgcount << __ffs(pgsize);
> > int flags = ZPCI_PTE_INVALID;
> > phys_addr_t paddr;
> > int rc;
> >
> > + if (iova < s390_domain->domain.geometry.aperture_start ||
> > + (iova + size - 1) > s390_domain->domain.geometry.aperture_end)
> > + return 0;
> > +
>
> Overall this LGTM and runs well with my testing. But I'm curious why we silently ignore an egregiously bad unmap request here? We've already done an -EINVAL for an attempt to map_pages() something outside of the aperture. If something still tries to unmap_pages() outside of the aperture, that seems like a bug? Maybe this should be surrounded by a if (WARN_ON(... || ...) to signify the unexpected behavior and then still return 0?
>
Well, the problem here is that .unmap_pages() returns size_t so
0 is kind of the only invalid value.But yes, a WARN_ON() seems
warranted.
> Otherwise:
> Reviewed-by: Matthew Rosato <mjrosato@...ux.ibm.com>
>
> > paddr = s390_iommu_iova_to_phys(domain, iova);
> > if (!paddr)
> > return 0;
> >
> > rc = s390_iommu_update_trans(s390_domain, paddr, iova,
> > - size, flags);
> > + pgcount, flags);
> > if (rc)
> > return 0;
> >
> > @@ -354,8 +370,8 @@ static const struct iommu_ops s390_iommu_ops = {
> > .default_domain_ops = &(const struct iommu_domain_ops) {
> > .attach_dev = s390_iommu_attach_device,
> > .detach_dev = s390_iommu_detach_device,
> > - .map = s390_iommu_map,
> > - .unmap = s390_iommu_unmap,
> > + .map_pages = s390_iommu_map_pages,
> > + .unmap_pages = s390_iommu_unmap_pages,
> > .iova_to_phys = s390_iommu_iova_to_phys,
> > .free = s390_domain_free,
> > }
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