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: Ian Campbell <ian.campbell@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
arch/x86/xen/Kconfig | 8 ++++++++
arch/x86/xen/mmu.c | 38 ++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+), 0 deletions(-)
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index 5b54892..e4343fe 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -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.
diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index b13b6ca..0c376a2 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -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;
--
1.7.1
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