[PATCH 11/15] KVM: PPC: e500: Support large page mappings of PFNMAP vmas.

Alexander Graf
2011-06-17T14:50:04Z

From: Scott Wood <scottwood@freescale.com>

This allows large pages to be used on guest mappings backed by things like
/dev/mem, resulting in a significant speedup when guest memory
is mapped this way (it's useful for directly-assigned MMIO, too).

This is not a substitute for hugetlbfs integration, but is useful for
configurations where devices are directly assigned on chips without an
IOMMU -- in these cases, we need guest physical and true physical to
match, and be contiguous, so static reservation and mapping via /dev/mem
is the most straightforward way to set things up.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
---
arch/powerpc/kvm/e500_tlb.c | 103 +++++++++++++++++++++++++++++++++++++++----
1 files changed, 94 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kvm/e500_tlb.c b/arch/powerpc/kvm/e500_tlb.c
index 0291c3c..7f808c5 100644
--- a/arch/powerpc/kvm/e500_tlb.c
+++ b/arch/powerpc/kvm/e500_tlb.c
@@ -270,28 +270,113 @@ static inline void kvmppc_e500_deliver_tlb_miss(struct kvm_vcpu *vcpu,
static inline void kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
u64 gvaddr, gfn_t gfn, struct tlbe *gtlbe, int tlbsel, int esel)
{
+ struct kvm_memory_slot *slot;
struct tlbe *stlbe;
- unsigned long pfn;
+ unsigned long pfn, hva;
+ int pfnmap = 0;
+ int tsize = BOOK3E_PAGESZ_4K;

stlbe = &vcpu_e500->shadow_tlb[tlbsel][esel];

/*
* Translate guest physical to true physical, acquiring
* a page reference if it is normal, non-reserved memory.
+ *
+ * gfn_to_memslot() must succeed because otherwise we wouldn't
+ * have gotten this far. Eventually we should just pass the slot
+ * pointer through from the first lookup.
*/
- pfn = gfn_to_pfn(vcpu_e500->vcpu.kvm, gfn);
- if (is_error_pfn(pfn)) {
- printk(KERN_ERR "Couldn't get real page for gfn %lx!\n",
- (long)gfn);
- kvm_release_pfn_clean(pfn);
- return;
+ slot = gfn_to_memslot(vcpu_e500->vcpu.kvm, gfn);
+ hva = gfn_to_hva_memslot(slot, gfn);
+
+ if (tlbsel == 1) {
+ struct vm_area_struct *vma;
+ down_read(&current->mm->mmap_sem);
+
+ vma = find_vma(current->mm, hva);
+ if (vma && hva >= vma->vm_start &&
+ (vma->vm_flags & VM_PFNMAP)) {
+ /*
+ * This VMA is a physically contiguous region (e.g.
+ * /dev/mem) that bypasses normal Linux page
+ * management. Find the overlap between the
+ * vma and the memslot.
+ */
+
+ unsigned long start, end;
+ unsigned long slot_start, slot_end;
+
+ pfnmap = 1;
+
+ start = vma->vm_pgoff;
+ end = start +
+ ((vma->vm_end - vma->vm_start) >> PAGE_SHIFT);
+
+ pfn = start + ((hva - vma->vm_start) >> PAGE_SHIFT);
+
+ slot_start = pfn - (gfn - slot->base_gfn);
+ slot_end = slot_start + slot->npages;
+
+ if (start < slot_start)
+ start = slot_start;
+ if (end > slot_end)
+ end = slot_end;
+
+ tsize = (gtlbe->mas1 & MAS1_TSIZE_MASK) >>
+ MAS1_TSIZE_SHIFT;
+
+ /*
+ * e500 doesn't implement the lowest tsize bit,
+ * or 1K pages.
+ */
+ tsize = max(BOOK3E_PAGESZ_4K, tsize & ~1);
+
+ /*
+ * Now find the largest tsize (up to what the guest
+ * requested) that will cover gfn, stay within the
+ * range, and for which gfn and pfn are mutually
+ * aligned.
+ */
+
+ for (; tsize > BOOK3E_PAGESZ_4K; tsize -= 2) {
+ unsigned long gfn_start, gfn_end, tsize_pages;
+ tsize_pages = 1 << (tsize - 2);
+
+ gfn_start = gfn & ~(tsize_pages - 1);
+ gfn_end = gfn_start + tsize_pages;
+
+ if (gfn_start + pfn - gfn < start)
+ continue;
+ if (gfn_end + pfn - gfn > end)
+ continue;
+ if ((gfn & (tsize_pages - 1)) !=
+ (pfn & (tsize_pages - 1)))
+ continue;
+
+ gvaddr &= ~((tsize_pages << PAGE_SHIFT) - 1);
+ pfn &= ~(tsize_pages - 1);
+ break;
+ }
+ }
+
+ up_read(&current->mm->mmap_sem);
+ }
+
+ if (likely(!pfnmap)) {
+ pfn = gfn_to_pfn_memslot(vcpu_e500->vcpu.kvm, slot, gfn);
+ if (is_error_pfn(pfn)) {
+ printk(KERN_ERR "Couldn't get real page for gfn %lx!\n",
+ (long)gfn);
+ kvm_release_pfn_clean(pfn);
+ return;
+ }
}

/* Drop reference to old page. */
kvmppc_e500_shadow_release(vcpu_e500, tlbsel, esel);

- /* Force TS=1 IPROT=0 TSIZE=4KB for all guest mappings. */
- stlbe->mas1 = MAS1_TSIZE(BOOK3E_PAGESZ_4K)
+ /* Force TS=1 IPROT=0 for all guest mappings. */
+ stlbe->mas1 = MAS1_TSIZE(tsize)
| MAS1_TID(get_tlb_tid(gtlbe)) | MAS1_TS | MAS1_VALID;
stlbe->mas2 = (gvaddr & MAS2_EPN)
| e500_shadow_mas2_attrib(gtlbe->mas2,
--
1.6.0.2