[Xen-devel] [PATCH 02/11] xen/x86: Use memblock_reserve for sensitive areas.

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

instead of a big memblock_reserve. This way we can be more
selective in freeing regions (and it also makes it easier
to understand where is what).

[v1: Move the auto_translate_physmap to proper line]
[v2: Per Stefano suggestion add more comments]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/enlighten.c |   48 ++++++++++++++++++++++++++++++++++++++++++++++
 arch/x86/xen/p2m.c       |    5 ++++
 arch/x86/xen/setup.c     |    9 --------
 3 files changed, 53 insertions(+), 9 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index ff962d4..e532eb5 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -998,7 +998,54 @@ static int xen_write_msr_safe(unsigned int msr, unsigned 
low, unsigned high)
 
        return ret;
 }
+/*
+ * If the MFN is not in the m2p (provided to us by the hypervisor) this
+ * function won't do anything. In practice this means that the XenBus
+ * MFN won't be available for the initial domain. */
+static void __init xen_reserve_mfn(unsigned long mfn)
+{
+       unsigned long pfn;
+
+       if (!mfn)
+               return;
+       pfn = mfn_to_pfn(mfn);
+       if (phys_to_machine_mapping_valid(pfn))
+               memblock_reserve(PFN_PHYS(pfn), PAGE_SIZE);
+}
+static void __init xen_reserve_internals(void)
+{
+       unsigned long size;
+
+       if (!xen_pv_domain())
+               return;
+
+       /* xen_start_info does not exist in the M2P, hence can't use
+        * xen_reserve_mfn. */
+       memblock_reserve(__pa(xen_start_info), PAGE_SIZE);
+
+       xen_reserve_mfn(PFN_DOWN(xen_start_info->shared_info));
+       xen_reserve_mfn(xen_start_info->store_mfn);
 
+       if (!xen_initial_domain())
+               xen_reserve_mfn(xen_start_info->console.domU.mfn);
+
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               return;
+
+       /*
+        * ALIGN up to compensate for the p2m_page pointing to an array that
+        * can partially filled (look in xen_build_dynamic_phys_to_machine).
+        */
+
+       size = PAGE_ALIGN(xen_start_info->nr_pages * sizeof(unsigned long));
+
+       /* We could use xen_reserve_mfn here, but would end up looping quite
+        * a lot (and call memblock_reserve for each PAGE), so lets just use
+        * the easy way and reserve it wholesale. */
+       memblock_reserve(__pa(xen_start_info->mfn_list), size);
+
+       /* The pagetables are reserved in mmu.c */
+}
 void xen_setup_shared_info(void)
 {
        if (!xen_feature(XENFEAT_auto_translated_physmap)) {
@@ -1362,6 +1409,7 @@ asmlinkage void __init xen_start_kernel(void)
        xen_raw_console_write("mapping kernel into physical memory\n");
        pgd = xen_setup_kernel_pagetable(pgd, xen_start_info->nr_pages);
 
+       xen_reserve_internals();
        /* Allocate and initialize top and mid mfn levels for p2m structure */
        xen_build_mfn_list_list();
 
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index e4adbfb..6a2bfa4 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -388,6 +388,11 @@ void __init xen_build_dynamic_phys_to_machine(void)
        }
 
        m2p_override_init();
+
+       /* NOTE: We cannot call memblock_reserve here for the mfn_list as there
+        * isn't enough pieces to make it work (for one - we are still using the
+        * Xen provided pagetable). Do it later in xen_reserve_internals.
+        */
 }
 
 unsigned long get_phys_to_machine(unsigned long pfn)
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index a4790bf..9efca75 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -424,15 +424,6 @@ char * __init xen_memory_setup(void)
        e820_add_region(ISA_START_ADDRESS, ISA_END_ADDRESS - ISA_START_ADDRESS,
                        E820_RESERVED);
 
-       /*
-        * Reserve Xen bits:
-        *  - mfn_list
-        *  - xen_start_info
-        * See comment above "struct start_info" in <xen/interface/xen.h>
-        */
-       memblock_reserve(__pa(xen_start_info->mfn_list),
-                        xen_start_info->pt_base - xen_start_info->mfn_list);
-
        sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 
        return "Xen";
-- 
1.7.7.6


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