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Commit fc25151d authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

xen/debug: WARN_ON when identity PFN has no _PAGE_IOMAP flag set. 



Only enabled if XEN_DEBUG is enabled. We print a warning
when:

 pfn_to_mfn(pfn) == pfn, but no VM_IO (_PAGE_IOMAP) flag set
	(and pfn is an identity mapped pfn)
 pfn_to_mfn(pfn) != pfn, and VM_IO flag is set.
	(ditto, pfn is an identity mapped pfn)

[v2: Make it dependent on CONFIG_XEN_DEBUG instead of ..DEBUG_FS]
[v3: Fix compiler warning]

Reviewed-by: default avatarIan Campbell <ian.campbell@citrix.com>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 2222e71b

arch/x86/xen/Kconfig

+8 −0
Original line number Diff line number Diff line
@@ -48,3 +48,11 @@ config XEN_DEBUG_FS 
	help

	  Enable statistics output and various tuning options in debugfs.

	  Enabling this option may incur a significant performance overhead.



config XEN_DEBUG

	bool "Enable Xen debug checks"

	depends on XEN

	default n

	help

	  Enable various WARN_ON checks in the Xen MMU code.

	  Enabling this option WILL incur a significant performance overhead.

arch/x86/xen/mmu.c

+38 −0
Original line number Diff line number Diff line
@@ -547,6 +547,41 @@ pte_t xen_make_pte(pteval_t pte) 
}

PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte);



#ifdef CONFIG_XEN_DEBUG

pte_t xen_make_pte_debug(pteval_t pte)

{

	phys_addr_t addr = (pte & PTE_PFN_MASK);

	phys_addr_t other_addr;

	bool io_page = false;

	pte_t _pte;



	if (pte & _PAGE_IOMAP)

		io_page = true;



	_pte = xen_make_pte(pte);



	if (!addr)

		return _pte;



	if (io_page &&

	    (xen_initial_domain() || addr >= ISA_END_ADDRESS)) {

		other_addr = pfn_to_mfn(addr >> PAGE_SHIFT) << PAGE_SHIFT;

		WARN(addr != other_addr,

			"0x%lx is using VM_IO, but it is 0x%lx!\n",

			(unsigned long)addr, (unsigned long)other_addr);

	} else {

		pteval_t iomap_set = (_pte.pte & PTE_FLAGS_MASK) & _PAGE_IOMAP;

		other_addr = (_pte.pte & PTE_PFN_MASK);

		WARN((addr == other_addr) && (!io_page) && (!iomap_set),

			"0x%lx is missing VM_IO (and wasn't fixed)!\n",

			(unsigned long)addr);

	}



	return _pte;

}

PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte_debug);

#endif



pgd_t xen_make_pgd(pgdval_t pgd)

{

	pgd = pte_pfn_to_mfn(pgd);
@@ -1957,6 +1992,9 @@ __init void xen_ident_map_ISA(void) 


static __init void xen_post_allocator_init(void)

{

#ifdef CONFIG_XEN_DEBUG

	pv_mmu_ops.make_pte = PV_CALLEE_SAVE(xen_make_pte_debug);

#endif

	pv_mmu_ops.set_pte = xen_set_pte;

	pv_mmu_ops.set_pmd = xen_set_pmd;

	pv_mmu_ops.set_pud = xen_set_pud;