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tools: Make restore work properly with PV superpage flag
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For PV guests, the superpage flag means to unconditionally allocate all
pages as superpages, which is required for Linux hugepages to work.  Support
for this on restore was not supported.  This patch adds proper support for
the superpage flag on restore.

For HVM guests, the superpage flag has been used to mean attempt to allocate
superpages if possible on restore.  This functionality has been preserved.

Signed-off-by: Dave McCracken <dave.mccracken@oracle.com>
Acked-by: George Dunlap <george.dunlap@eu.citrix.com>
Committed-by: Ian Campbell <ian.campbell@citrix.com>
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@dcmccracken
dcmccracken committed Nov 12, 2012
1 parent 6bdf54c commit 022ad16
Showing 1 changed file with 101 additions and 29 deletions.
130 changes: 101 additions & 29 deletions tools/libxc/xc_domain_restore.c
View file
Expand Up @@ -23,6 +23,19 @@
*
*/

/*
* The superpages flag in restore has two different meanings depending on
* the type of domain.
*
* For an HVM domain, the flag means to look for properly aligned contiguous
* pages and try to allocate a superpage to satisfy it. If that fails,
* fall back to small pages.
*
* For a PV domain, the flag means allocate all memory as superpages. If that
* fails, the restore fails. This behavior is required for PV guests who
* want to use superpages.
*/

#include <stdlib.h>
#include <unistd.h>

Expand All @@ -41,6 +54,9 @@ struct restore_ctx {
xen_pfn_t *live_p2m; /* Live mapping of the table mapping each PFN to its current MFN. */
xen_pfn_t *p2m; /* A table mapping each PFN to its new MFN. */
xen_pfn_t *p2m_batch; /* A table of P2M mappings in the current region. */
xen_pfn_t *p2m_saved_batch; /* Copy of p2m_batch array for pv superpage alloc */
int superpages; /* Superpage allocation has been requested */
int hvm; /* This is an hvm domain */
int completed; /* Set when a consistent image is available */
int last_checkpoint; /* Set when we should commit to the current checkpoint when it completes. */
int compressing; /* Set when sender signals that pages would be sent compressed (for Remus) */
Expand All @@ -49,11 +65,6 @@ struct restore_ctx {

#define HEARTBEAT_MS 1000

#define SUPERPAGE_PFN_SHIFT 9
#define SUPERPAGE_NR_PFNS (1UL << SUPERPAGE_PFN_SHIFT)

#define SUPER_PAGE_START(pfn) (((pfn) & (SUPERPAGE_NR_PFNS-1)) == 0 )

#ifndef __MINIOS__
static ssize_t rdexact(xc_interface *xch, struct restore_ctx *ctx,
int fd, void* buf, size_t size)
Expand Down Expand Up @@ -103,6 +114,49 @@ static ssize_t rdexact(xc_interface *xch, struct restore_ctx *ctx,
#else
#define RDEXACT read_exact
#endif

#define SUPERPAGE_PFN_SHIFT 9
#define SUPERPAGE_NR_PFNS (1UL << SUPERPAGE_PFN_SHIFT)
#define SUPERPAGE(_pfn) ((_pfn) & (~(SUPERPAGE_NR_PFNS-1)))
#define SUPER_PAGE_START(pfn) (((pfn) & (SUPERPAGE_NR_PFNS-1)) == 0 )

/*
** When we're restoring into a pv superpage-allocated guest, we take
** a copy of the p2m_batch array to preserve the pfn, then allocate the
** corresponding superpages. We then fill in the p2m array using the saved
** pfns.
*/
static int alloc_superpage_mfns(
xc_interface *xch, uint32_t dom, struct restore_ctx *ctx, int nr_mfns)
{
int i, j, max = 0;
unsigned long pfn, base_pfn, mfn;

for (i = 0; i < nr_mfns; i++)
{
pfn = ctx->p2m_batch[i];
base_pfn = SUPERPAGE(pfn);
if (ctx->p2m[base_pfn] != (INVALID_P2M_ENTRY-2))
{
ctx->p2m_saved_batch[max] = base_pfn;
ctx->p2m_batch[max] = base_pfn;
max++;
ctx->p2m[base_pfn] = INVALID_P2M_ENTRY-2;
}
}
if (xc_domain_populate_physmap_exact(xch, dom, max, SUPERPAGE_PFN_SHIFT,
0, ctx->p2m_batch) != 0)
return 1;

for (i = 0; i < max; i++)
{
mfn = ctx->p2m_batch[i];
pfn = ctx->p2m_saved_batch[i];
for (j = 0; j < SUPERPAGE_NR_PFNS; j++)
ctx->p2m[pfn++] = mfn++;
}
return 0;
}
/*
** In the state file (or during transfer), all page-table pages are
** converted into a 'canonical' form where references to actual mfns
Expand All @@ -113,7 +167,7 @@ static ssize_t rdexact(xc_interface *xch, struct restore_ctx *ctx,
static int uncanonicalize_pagetable(
xc_interface *xch, uint32_t dom, struct restore_ctx *ctx, void *page)
{
int i, pte_last, nr_mfns = 0;
int i, rc, pte_last, nr_mfns = 0;
unsigned long pfn;
uint64_t pte;
struct domain_info_context *dinfo = &ctx->dinfo;
Expand Down Expand Up @@ -152,13 +206,20 @@ static int uncanonicalize_pagetable(
}

/* Allocate the requisite number of mfns. */
if ( nr_mfns &&
(xc_domain_populate_physmap_exact(xch, dom, nr_mfns, 0, 0,
ctx->p2m_batch) != 0) )
{
ERROR("Failed to allocate memory for batch.!\n");
errno = ENOMEM;
return 0;
if (nr_mfns)
{
if (!ctx->hvm && ctx->superpages)
rc = alloc_superpage_mfns(xch, dom, ctx, nr_mfns);
else
rc = xc_domain_populate_physmap_exact(xch, dom, nr_mfns, 0, 0,
ctx->p2m_batch);

if (rc)
{
ERROR("Failed to allocate memory for batch.!\n");
errno = ENOMEM;
return 0;
}
}

/* Second pass: uncanonicalize each present PTE */
Expand Down Expand Up @@ -1018,8 +1079,8 @@ static int pagebuf_get(xc_interface *xch, struct restore_ctx *ctx,

static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
xen_pfn_t* region_mfn, unsigned long* pfn_type, int pae_extended_cr3,
unsigned int hvm, struct xc_mmu* mmu,
pagebuf_t* pagebuf, int curbatch, int superpages)
struct xc_mmu* mmu,
pagebuf_t* pagebuf, int curbatch)
{
int i, j, curpage, nr_mfns;
int k, scount;
Expand Down Expand Up @@ -1061,7 +1122,7 @@ static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
/* Is this the next expected continuation? */
if ( pfn == superpage_start + scount )
{
if ( !superpages )
if ( !ctx->superpages )
{
ERROR("Unexpexted codepath with no superpages");
return -1;
Expand Down Expand Up @@ -1114,16 +1175,17 @@ static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
}

/* Are we ready to start a new superpage candidate? */
if ( superpages && SUPER_PAGE_START(pfn) )
if ( ctx->hvm && ctx->superpages && SUPER_PAGE_START(pfn) )
{
superpage_start=pfn;
scount++;
continue;
}

/* Add the current pfn to pfn_batch */
ctx->p2m_batch[nr_mfns++] = pfn;
ctx->p2m[pfn]--;
else
{
/* Add the current pfn to pfn_batch */
ctx->p2m_batch[nr_mfns++] = pfn;
ctx->p2m[pfn]--;
}
}
}

Expand All @@ -1144,9 +1206,14 @@ static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
{
DPRINTF("Mapping order 0, %d; first pfn %lx\n", nr_mfns, ctx->p2m_batch[0]);

if(xc_domain_populate_physmap_exact(xch, dom, nr_mfns, 0,
0, ctx->p2m_batch) != 0)
{
if (!ctx->hvm && ctx->superpages)
rc = alloc_superpage_mfns(xch, dom, ctx, nr_mfns);
else
rc = xc_domain_populate_physmap_exact(xch, dom, nr_mfns, 0, 0,
ctx->p2m_batch);

if (rc)
{
ERROR("Failed to allocate memory for batch.!\n");
errno = ENOMEM;
return -1;
Expand Down Expand Up @@ -1175,7 +1242,7 @@ static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
|| pagetype == XEN_DOMCTL_PFINFO_XALLOC )
region_mfn[i] = ~0UL; /* map will fail but we don't care */
else
region_mfn[i] = hvm ? pfn : ctx->p2m[pfn];
region_mfn[i] = ctx->hvm ? pfn : ctx->p2m[pfn];
}

/* Map relevant mfns */
Expand Down Expand Up @@ -1298,7 +1365,7 @@ static int apply_batch(xc_interface *xch, uint32_t dom, struct restore_ctx *ctx,
}
}

if ( !hvm &&
if ( !ctx->hvm &&
xc_add_mmu_update(xch, mmu,
(((unsigned long long)mfn) << PAGE_SHIFT)
| MMU_MACHPHYS_UPDATE, pfn) )
Expand Down Expand Up @@ -1389,6 +1456,9 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,

memset(ctx, 0, sizeof(*ctx));

ctx->superpages = superpages;
ctx->hvm = hvm;

ctxt = xc_hypercall_buffer_alloc(xch, ctxt, sizeof(*ctxt));

if ( ctxt == NULL )
Expand Down Expand Up @@ -1452,6 +1522,9 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,

region_mfn = malloc(ROUNDUP(MAX_BATCH_SIZE * sizeof(xen_pfn_t), PAGE_SHIFT));
ctx->p2m_batch = malloc(ROUNDUP(MAX_BATCH_SIZE * sizeof(xen_pfn_t), PAGE_SHIFT));
if (!ctx->hvm && ctx->superpages)
ctx->p2m_saved_batch =
malloc(ROUNDUP(MAX_BATCH_SIZE * sizeof(xen_pfn_t), PAGE_SHIFT));

if ( (ctx->p2m == NULL) || (pfn_type == NULL) ||
(region_mfn == NULL) || (ctx->p2m_batch == NULL) )
Expand Down Expand Up @@ -1575,8 +1648,7 @@ int xc_domain_restore(xc_interface *xch, int io_fd, uint32_t dom,
int brc;

brc = apply_batch(xch, dom, ctx, region_mfn, pfn_type,
pae_extended_cr3, hvm, mmu, &pagebuf, curbatch,
superpages);
pae_extended_cr3, mmu, &pagebuf, curbatch);
if ( brc < 0 )
goto out;

Expand Down

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