Jan Beulich wrote:
Don't rely on kmalloc(PAGE_SIZE) returning PAGE_SIZE aligned memory
(Xen requires GDT *and* LDT to be page-aligned).
Can kmalloc return non-page-aligned PAGE_SIZE allocations?
Using the page
allocator interface also removes the (albeit small) slab allocator
overhead.
Runtime or space overhead? Given that they're once-off allocations, the
time part isn't a big factor. And apparently LDT is completely unused.
Seems like a reasonable change either way.
The same change being done for 64-bits for consistency.
Further, the Xen hypercall interface expects the LDT address to be
virtual, not machine.
Shows how much the LDT gets used then... Hm, but I didn't make that
code up; I wonder where it came from? But certainly, passing the mfn of
the first page of a vmalloc area doesn't make any sense.
Signed-off-by: Jan Beulich <[EMAIL PROTECTED]>
Cc: Ingo Molnar <[EMAIL PROTECTED]>
Acked-by: Jeremy Fitzhardinge <[EMAIL PROTECTED]>
---
arch/x86/kernel/ldt_32.c | 7 +++----
arch/x86/kernel/ldt_64.c | 7 +++----
arch/x86/xen/enlighten.c | 9 +--------
3 files changed, 7 insertions(+), 16 deletions(-)
--- linux-2.6.24-rc7/arch/x86/kernel/ldt_32.c 2008-01-10 16:53:54.000000000
+0100
+++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_32.c 2008-01-09
13:59:50.000000000 +0100
@@ -9,7 +9,6 @@
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/vmalloc.h>
-#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/system.h>
@@ -38,7 +37,7 @@ static int alloc_ldt(mm_context_t *pc, i
if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
else
- newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
+ newldt = (void *)__get_free_page(GFP_KERNEL);
if (!newldt)
return -ENOMEM;
@@ -69,7 +68,7 @@ static int alloc_ldt(mm_context_t *pc, i
if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(oldldt);
else
- kfree(oldldt);
+ put_page(virt_to_page(oldldt));
}
return 0;
}
@@ -114,7 +113,7 @@ void destroy_context(struct mm_struct *m
if (mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(mm->context.ldt);
else
- kfree(mm->context.ldt);
+ put_page(virt_to_page(mm->context.ldt));
mm->context.size = 0;
}
}
--- linux-2.6.24-rc7/arch/x86/kernel/ldt_64.c 2008-01-10 16:53:54.000000000
+0100
+++ 2.6.24-rc7-x86-xen-ldt/arch/x86/kernel/ldt_64.c 2008-01-09
13:59:50.000000000 +0100
@@ -12,7 +12,6 @@
#include <linux/mm.h>
#include <linux/smp.h>
#include <linux/vmalloc.h>
-#include <linux/slab.h>
#include <asm/uaccess.h>
#include <asm/system.h>
@@ -41,7 +40,7 @@ static int alloc_ldt(mm_context_t *pc, u
if (mincount*LDT_ENTRY_SIZE > PAGE_SIZE)
newldt = vmalloc(mincount*LDT_ENTRY_SIZE);
else
- newldt = kmalloc(mincount*LDT_ENTRY_SIZE, GFP_KERNEL);
+ newldt = (void *)__get_free_page(GFP_KERNEL);
if (!newldt)
return -ENOMEM;
@@ -73,7 +72,7 @@ static int alloc_ldt(mm_context_t *pc, u
if (oldsize*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(oldldt);
else
- kfree(oldldt);
+ put_page(virt_to_page(oldldt));
}
return 0;
}
@@ -117,7 +116,7 @@ void destroy_context(struct mm_struct *m
if ((unsigned)mm->context.size*LDT_ENTRY_SIZE > PAGE_SIZE)
vfree(mm->context.ldt);
else
- kfree(mm->context.ldt);
+ put_page(virt_to_page(mm->context.ldt));
mm->context.size = 0;
}
}
--- linux-2.6.24-rc7/arch/x86/xen/enlighten.c 2008-01-10 16:53:55.000000000
+0100
+++ 2.6.24-rc7-x86-xen-ldt/arch/x86/xen/enlighten.c 2008-01-09
14:00:51.000000000 +0100
@@ -275,19 +275,12 @@ static unsigned long xen_store_tr(void)
static void xen_set_ldt(const void *addr, unsigned entries)
{
- unsigned long linear_addr = (unsigned long)addr;
struct mmuext_op *op;
struct multicall_space mcs = xen_mc_entry(sizeof(*op));
op = mcs.args;
op->cmd = MMUEXT_SET_LDT;
- if (linear_addr) {
- /* ldt my be vmalloced, use arbitrary_virt_to_machine */
- xmaddr_t maddr;
- maddr = arbitrary_virt_to_machine((unsigned long)addr);
- linear_addr = (unsigned long)maddr.maddr;
- }
- op->arg1.linear_addr = linear_addr;
+ op->arg1.linear_addr = (unsigned long)addr;
op->arg2.nr_ents = entries;
MULTI_mmuext_op(mcs.mc, op, 1, NULL, DOMID_SELF);
--
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