Re: [Xen-devel] [Patch V2 10/15] xen: check pre-allocated page tables for conflict with memory map
From: Juergen Gross
Date: Thu Apr 09 2015 - 09:09:09 EST
On 04/09/2015 02:47 PM, David Vrabel wrote:
On 09/04/2015 07:55, Juergen Gross wrote:
Check whether the page tables built by the domain builder are at
memory addresses which are in conflict with the target memory map.
If this is the case just panic instead of running into problems
later.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
arch/x86/xen/mmu.c | 19 ++++++++++++++++---
arch/x86/xen/setup.c | 6 ++++++
arch/x86/xen/xen-ops.h | 1 +
3 files changed, 23 insertions(+), 3 deletions(-)
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 1ca5197..41aeb1c 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -116,6 +116,7 @@ static pud_t level3_user_vsyscall[PTRS_PER_PUD] __page_aligned_bss;
DEFINE_PER_CPU(unsigned long, xen_cr3); /* cr3 stored as physaddr */
DEFINE_PER_CPU(unsigned long, xen_current_cr3); /* actual vcpu cr3 */
+static phys_addr_t xen_pt_base, xen_pt_size;
These be __init, but the use of globals in this way is confusing.
How else would you want to do it?
/*
* Just beyond the highest usermode address. STACK_TOP_MAX has a
@@ -1998,7 +1999,9 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
check_pt_base(&pt_base, &pt_end, addr[i]);
/* Our (by three pages) smaller Xen pagetable that we are using */
- memblock_reserve(PFN_PHYS(pt_base), (pt_end - pt_base) * PAGE_SIZE);
+ xen_pt_base = PFN_PHYS(pt_base);
+ xen_pt_size = (pt_end - pt_base) * PAGE_SIZE;
+ memblock_reserve(xen_pt_base, xen_pt_size);
Why not provide a xen_memblock_check_and_reserve() call that has the
xen_is_e820_reserved() check and the memblock_reserve() call? This may
also be useful for patch #9 as well.
Uuh, not really. memblock_reserve() for those areas is called much
earlier than the e820 map is constructed.
Thinking more about it, I even have to modify patch 11 and 13:
relocation must be done _after_ doing the memblock_reserve() of all
pre-populated areas to avoid relocating to such an area.
Juergen
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