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Date: Tue, 21 Dec 2010 14:41:23 -0800
From: Jeremy Fitzhardinge <jeremy@...p.org>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC: linux-kernel@...r.kernel.org, hpa@...or.com,
Jan Beulich <JBeulich@...ell.com>,
xen-devel@...ts.xensource.com,
Konrad Rzeszutek Wilk <konrad@...nel.org>
Subject: Re: [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@...nel.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@...cle.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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