xen/privcmd: improve performance of MMAPBATCH_V2
Make the IOCTL_PRIVCMD_MMAPBATCH_V2 (and older V1 version) map
multiple frames at a time rather than one at a time, despite the pages
being non-consecutive GFNs.
xen_remap_foreign_mfn_array() is added which maps an array of GFNs
(instead of a consecutive range of GFNs).
Since per-frame errors are returned in an array, privcmd must set the
MMAPBATCH_V1 error bits as part of the "report errors" phase, after
all the frames are mapped.
Migrate times are significantly improved (when using a PV toolstack
domain). For example, for an idle 12 GiB PV guest:
Before After
real 0m38.179s 0m26.868s
user 0m15.096s 0m13.652s
sys 0m28.988s 0m18.732s
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 3d536a5..29b3be2 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -2439,7 +2439,8 @@
#define REMAP_BATCH_SIZE 16
struct remap_data {
- unsigned long mfn;
+ xen_pfn_t *mfn;
+ bool contiguous;
pgprot_t prot;
struct mmu_update *mmu_update;
};
@@ -2448,7 +2449,14 @@
unsigned long addr, void *data)
{
struct remap_data *rmd = data;
- pte_t pte = pte_mkspecial(mfn_pte(rmd->mfn++, rmd->prot));
+ pte_t pte = pte_mkspecial(mfn_pte(*rmd->mfn, rmd->prot));
+
+ /* If we have a contigious range, just update the mfn itself,
+ else update pointer to be "next mfn". */
+ if (rmd->contiguous)
+ (*rmd->mfn)++;
+ else
+ rmd->mfn++;
rmd->mmu_update->ptr = virt_to_machine(ptep).maddr;
rmd->mmu_update->val = pte_val_ma(pte);
@@ -2457,26 +2465,26 @@
return 0;
}
-int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
- unsigned long addr,
- xen_pfn_t mfn, int nr,
- pgprot_t prot, unsigned domid,
- struct page **pages)
-
+static int do_remap_mfn(struct vm_area_struct *vma,
+ unsigned long addr,
+ xen_pfn_t *mfn, int nr,
+ int *err_ptr, pgprot_t prot,
+ unsigned domid,
+ struct page **pages)
{
+ int err = 0;
struct remap_data rmd;
struct mmu_update mmu_update[REMAP_BATCH_SIZE];
- int batch;
unsigned long range;
- int err = 0;
+ int mapped = 0;
BUG_ON(!((vma->vm_flags & (VM_PFNMAP | VM_IO)) == (VM_PFNMAP | VM_IO)));
if (xen_feature(XENFEAT_auto_translated_physmap)) {
#ifdef CONFIG_XEN_PVH
/* We need to update the local page tables and the xen HAP */
- return xen_xlate_remap_gfn_range(vma, addr, mfn, nr, prot,
- domid, pages);
+ return xen_xlate_remap_gfn_array(vma, addr, mfn, nr, err_ptr,
+ prot, domid, pages);
#else
return -EINVAL;
#endif
@@ -2484,9 +2492,15 @@
rmd.mfn = mfn;
rmd.prot = prot;
+ /* We use the err_ptr to indicate if there we are doing a contigious
+ * mapping or a discontigious mapping. */
+ rmd.contiguous = !err_ptr;
while (nr) {
- batch = min(REMAP_BATCH_SIZE, nr);
+ int index = 0;
+ int done = 0;
+ int batch = min(REMAP_BATCH_SIZE, nr);
+ int batch_left = batch;
range = (unsigned long)batch << PAGE_SHIFT;
rmd.mmu_update = mmu_update;
@@ -2495,23 +2509,72 @@
if (err)
goto out;
- err = HYPERVISOR_mmu_update(mmu_update, batch, NULL, domid);
- if (err < 0)
- goto out;
+ /* We record the error for each page that gives an error, but
+ * continue mapping until the whole set is done */
+ do {
+ int i;
+
+ err = HYPERVISOR_mmu_update(&mmu_update[index],
+ batch_left, &done, domid);
+
+ /*
+ * @err_ptr may be the same buffer as @mfn, so
+ * only clear it after each chunk of @mfn is
+ * used.
+ */
+ if (err_ptr) {
+ for (i = index; i < index + done; i++)
+ err_ptr[i] = 0;
+ }
+ if (err < 0) {
+ if (!err_ptr)
+ goto out;
+ err_ptr[i] = err;
+ done++; /* Skip failed frame. */
+ } else
+ mapped += done;
+ batch_left -= done;
+ index += done;
+ } while (batch_left);
nr -= batch;
addr += range;
+ if (err_ptr)
+ err_ptr += batch;
}
-
- err = 0;
out:
xen_flush_tlb_all();
- return err;
+ return err < 0 ? err : mapped;
+}
+
+int xen_remap_domain_mfn_range(struct vm_area_struct *vma,
+ unsigned long addr,
+ xen_pfn_t mfn, int nr,
+ pgprot_t prot, unsigned domid,
+ struct page **pages)
+{
+ return do_remap_mfn(vma, addr, &mfn, nr, NULL, prot, domid, pages);
}
EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_range);
+int xen_remap_domain_mfn_array(struct vm_area_struct *vma,
+ unsigned long addr,
+ xen_pfn_t *mfn, int nr,
+ int *err_ptr, pgprot_t prot,
+ unsigned domid, struct page **pages)
+{
+ /* We BUG_ON because it's a programmer error to pass a NULL err_ptr,
+ * and the consequences later is quite hard to detect what the actual
+ * cause of "wrong memory was mapped in".
+ */
+ BUG_ON(err_ptr == NULL);
+ return do_remap_mfn(vma, addr, mfn, nr, err_ptr, prot, domid, pages);
+}
+EXPORT_SYMBOL_GPL(xen_remap_domain_mfn_array);
+
+
/* Returns: 0 success */
int xen_unmap_domain_mfn_range(struct vm_area_struct *vma,
int numpgs, struct page **pages)