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    SubjectRe: [PATCH 02/10] xen/p2m: change p2m_missing_* to p2m_identity_*
    On 12/21/2010 01:37 PM, Konrad Rzeszutek Wilk wrote:
    > From: Konrad Rzeszutek Wilk <konrad@kernel.org>
    >
    > We are going to alter how we think about P2M. Most of the
    > P2M contains MFN, and areas that are not populated are
    > considered to be "missing". Missing means that the PFN
    > is either not set for this guest (not have that much memory
    > allocated) or is under the balloon driver ownership.
    >
    > We are instead now going to think of those not populated
    > areas as "identity." Meaning that that the PFN for which
    > we would get the p2m_identity we will provide the the PFN
    > value back instead of P2M_MISSING. Essentially treating
    > those regions as PFN==MFN.
    >

    This renames missing -> identity, but does it actually change the
    functionality? Doesn't it just leave it being misnamed? It would
    probably be better to fold in the actual identity implementation as well.
    > Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
    > ---
    > arch/x86/xen/mmu.c | 59 ++++++++++++++++++++++++++-------------------------
    > 1 files changed, 30 insertions(+), 29 deletions(-)
    >
    > diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
    > index 44924e5..d6d0276 100644
    > --- a/arch/x86/xen/mmu.c
    > +++ b/arch/x86/xen/mmu.c
    > @@ -209,9 +209,9 @@ unsigned long xen_max_p2m_pfn __read_mostly;
    > #define MAX_P2M_PFN (P2M_TOP_PER_PAGE * P2M_MID_PER_PAGE * P2M_PER_PAGE)
    >
    > /* Placeholders for holes in the address space */
    > -static RESERVE_BRK_ARRAY(unsigned long, p2m_missing, P2M_PER_PAGE);
    > -static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_missing, P2M_MID_PER_PAGE);
    > -static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_missing_mfn, P2M_MID_PER_PAGE);
    > +static RESERVE_BRK_ARRAY(unsigned long, p2m_identity, P2M_PER_PAGE);
    > +static RESERVE_BRK_ARRAY(unsigned long *, p2m_mid_identity, P2M_MID_PER_PAGE);
    > +static RESERVE_BRK_ARRAY(unsigned long, p2m_mid_identity_mfn, P2M_MID_PER_PAGE);
    >
    > static RESERVE_BRK_ARRAY(unsigned long **, p2m_top, P2M_TOP_PER_PAGE);
    > static RESERVE_BRK_ARRAY(unsigned long, p2m_top_mfn, P2M_TOP_PER_PAGE);
    > @@ -241,7 +241,7 @@ static void p2m_top_init(unsigned long ***top)
    > unsigned i;
    >
    > for (i = 0; i < P2M_TOP_PER_PAGE; i++)
    > - top[i] = p2m_mid_missing;
    > + top[i] = p2m_mid_identity;
    > }
    >
    > static void p2m_top_mfn_init(unsigned long *top)
    > @@ -249,7 +249,7 @@ static void p2m_top_mfn_init(unsigned long *top)
    > unsigned i;
    >
    > for (i = 0; i < P2M_TOP_PER_PAGE; i++)
    > - top[i] = virt_to_mfn(p2m_mid_missing_mfn);
    > + top[i] = virt_to_mfn(p2m_mid_identity_mfn);
    > }
    >
    > static void p2m_top_mfn_p_init(unsigned long **top)
    > @@ -257,7 +257,7 @@ static void p2m_top_mfn_p_init(unsigned long **top)
    > unsigned i;
    >
    > for (i = 0; i < P2M_TOP_PER_PAGE; i++)
    > - top[i] = p2m_mid_missing_mfn;
    > + top[i] = p2m_mid_identity_mfn;
    > }
    >
    > static void p2m_mid_init(unsigned long **mid)
    > @@ -265,7 +265,7 @@ static void p2m_mid_init(unsigned long **mid)
    > unsigned i;
    >
    > for (i = 0; i < P2M_MID_PER_PAGE; i++)
    > - mid[i] = p2m_missing;
    > + mid[i] = p2m_identity;
    > }
    >
    > static void p2m_mid_mfn_init(unsigned long *mid)
    > @@ -273,7 +273,7 @@ static void p2m_mid_mfn_init(unsigned long *mid)
    > unsigned i;
    >
    > for (i = 0; i < P2M_MID_PER_PAGE; i++)
    > - mid[i] = virt_to_mfn(p2m_missing);
    > + mid[i] = virt_to_mfn(p2m_identity);
    > }
    >
    > static void p2m_init(unsigned long *p2m)
    > @@ -300,8 +300,8 @@ void xen_build_mfn_list_list(void)
    >
    > /* Pre-initialize p2m_top_mfn to be completely missing */
    > if (p2m_top_mfn == NULL) {
    > - p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > - p2m_mid_mfn_init(p2m_mid_missing_mfn);
    > + p2m_mid_identity_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > + p2m_mid_mfn_init(p2m_mid_identity_mfn);
    >
    > p2m_top_mfn_p = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > p2m_top_mfn_p_init(p2m_top_mfn_p);
    > @@ -310,7 +310,7 @@ void xen_build_mfn_list_list(void)
    > p2m_top_mfn_init(p2m_top_mfn);
    > } else {
    > /* Reinitialise, mfn's all change after migration */
    > - p2m_mid_mfn_init(p2m_mid_missing_mfn);
    > + p2m_mid_mfn_init(p2m_mid_identity_mfn);
    > }
    >
    > for (pfn = 0; pfn < xen_max_p2m_pfn; pfn += P2M_PER_PAGE) {
    > @@ -326,15 +326,15 @@ void xen_build_mfn_list_list(void)
    > * they're just missing, just update the stored mfn,
    > * since all could have changed over a migrate.
    > */
    > - if (mid == p2m_mid_missing) {
    > + if (mid == p2m_mid_identity) {
    > BUG_ON(mididx);
    > - BUG_ON(mid_mfn_p != p2m_mid_missing_mfn);
    > - p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_missing_mfn);
    > + BUG_ON(mid_mfn_p != p2m_mid_identity_mfn);
    > + p2m_top_mfn[topidx] = virt_to_mfn(p2m_mid_identity_mfn);
    > pfn += (P2M_MID_PER_PAGE - 1) * P2M_PER_PAGE;
    > continue;
    > }
    >
    > - if (mid_mfn_p == p2m_mid_missing_mfn) {
    > + if (mid_mfn_p == p2m_mid_identity_mfn) {
    > /*
    > * XXX boot-time only! We should never find
    > * missing parts of the mfn tree after
    > @@ -370,11 +370,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
    >
    > xen_max_p2m_pfn = max_pfn;
    >
    > - p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > - p2m_init(p2m_missing);
    > + p2m_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > + p2m_init(p2m_identity);
    >
    > - p2m_mid_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > - p2m_mid_init(p2m_mid_missing);
    > + p2m_mid_identity = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > + p2m_mid_init(p2m_mid_identity);
    >
    > p2m_top = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > p2m_top_init(p2m_top);
    > @@ -388,7 +388,7 @@ void __init xen_build_dynamic_phys_to_machine(void)
    > unsigned topidx = p2m_top_index(pfn);
    > unsigned mididx = p2m_mid_index(pfn);
    >
    > - if (p2m_top[topidx] == p2m_mid_missing) {
    > + if (p2m_top[topidx] == p2m_mid_identity) {
    > unsigned long **mid = extend_brk(PAGE_SIZE, PAGE_SIZE);
    > p2m_mid_init(mid);
    >
    > @@ -443,7 +443,7 @@ static bool alloc_p2m(unsigned long pfn)
    > top_p = &p2m_top[topidx];
    > mid = *top_p;
    >
    > - if (mid == p2m_mid_missing) {
    > + if (mid == p2m_mid_identity) {
    > /* Mid level is missing, allocate a new one */
    > mid = alloc_p2m_page();
    > if (!mid)
    > @@ -451,7 +451,7 @@ static bool alloc_p2m(unsigned long pfn)
    >
    > p2m_mid_init(mid);
    >
    > - if (cmpxchg(top_p, p2m_mid_missing, mid) != p2m_mid_missing)
    > + if (cmpxchg(top_p, p2m_mid_identity, mid) != p2m_mid_identity)
    > free_p2m_page(mid);
    > }
    >
    > @@ -460,9 +460,9 @@ static bool alloc_p2m(unsigned long pfn)
    >
    > BUG_ON(virt_to_mfn(mid_mfn) != *top_mfn_p);
    >
    > - if (mid_mfn == p2m_mid_missing_mfn) {
    > + if (mid_mfn == p2m_mid_identity_mfn) {
    > /* Separately check the mid mfn level */
    > - unsigned long missing_mfn;
    > + unsigned long identity_mfn;
    > unsigned long mid_mfn_mfn;
    >
    > mid_mfn = alloc_p2m_page();
    > @@ -471,15 +471,16 @@ static bool alloc_p2m(unsigned long pfn)
    >
    > p2m_mid_mfn_init(mid_mfn);
    >
    > - missing_mfn = virt_to_mfn(p2m_mid_missing_mfn);
    > + identity_mfn = virt_to_mfn(p2m_mid_identity_mfn);
    > mid_mfn_mfn = virt_to_mfn(mid_mfn);
    > - if (cmpxchg(top_mfn_p, missing_mfn, mid_mfn_mfn) != missing_mfn)
    > + if (cmpxchg(top_mfn_p, identity_mfn, mid_mfn_mfn) !=
    > + identity_mfn)

    Don't wrap this.

    > free_p2m_page(mid_mfn);
    > else
    > p2m_top_mfn_p[topidx] = mid_mfn;
    > }
    >
    > - if (p2m_top[topidx][mididx] == p2m_missing) {
    > + if (p2m_top[topidx][mididx] == p2m_identity) {
    > /* p2m leaf page is missing */
    > unsigned long *p2m;
    >
    > @@ -489,7 +490,7 @@ static bool alloc_p2m(unsigned long pfn)
    >
    > p2m_init(p2m);
    >
    > - if (cmpxchg(&mid[mididx], p2m_missing, p2m) != p2m_missing)
    > + if (cmpxchg(&mid[mididx], p2m_identity, p2m) != p2m_identity)
    > free_p2m_page(p2m);
    > else
    > mid_mfn[mididx] = virt_to_mfn(p2m);
    > @@ -512,7 +513,7 @@ bool __set_phys_to_machine(unsigned long pfn, unsigned long mfn)
    > mididx = p2m_mid_index(pfn);
    > idx = p2m_index(pfn);
    >
    > - if (p2m_top[topidx][mididx] == p2m_missing)
    > + if (p2m_top[topidx][mididx] == p2m_identity)
    > return mfn == INVALID_P2M_ENTRY;
    >
    > p2m_top[topidx][mididx][idx] = mfn;

    Thanks,
    J


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