[Xen-devel] [PATCH v11 04/12] xen/pvh: Don't setup P2M tree.

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

P2M is not available for PVH. Fortunatly for us the
P2M code already has mostly the support for auto-xlat guest thanks to
commit 3d24bbd7dddbea54358a9795abaf051b0f18973c
"grant-table: call set_phys_to_machine after mapping grant refs"
which: "
introduces set_phys_to_machine calls for auto_translated guests
(even on x86) in gnttab_map_refs and gnttab_unmap_refs.
translated by swiotlb-xen... " so we don't need to muck much.

But we still have to inhibit the building of the P2M tree.
That had been done in the past by not calling
xen_build_dynamic_phys_to_machine (which setups the P2M tree
and gives us virtual address to access them). But we are missing
a check for xen_build_mfn_list_list - which was continuing to setup
the P2M tree and would blow up at trying to get the virtual
address of p2m_missing (which would have been setup by
xen_build_dynamic_phys_to_machine).

Hence a check is needed to not call xen_build_mfn_list_list when
running in auto-xlat mode.

Instead of replicating the check for auto-xlat in enlighten.c
do it in the p2m.c code. The reason is that the xen_build_mfn_list_list
is called also in xen_arch_post_suspend without any checks for
auto-xlat. So for PVH or PV with auto-xlat - we would needlessly
allocate space for an P2M tree.

Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
---
 arch/x86/xen/enlighten.c |  3 +--
 arch/x86/xen/p2m.c       | 12 ++++++++++--
 2 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 3b21c82..c7341d0 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1493,8 +1493,7 @@ asmlinkage void __init xen_start_kernel(void)
        x86_configure_nx();
 
        /* Get mfn list */
-       if (!xen_feature(XENFEAT_auto_translated_physmap))
-               xen_build_dynamic_phys_to_machine();
+       xen_build_dynamic_phys_to_machine();
 
        /*
         * Set up kernel GDT and segment registers, mainly so that
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 2ae8699..fb7ee0a 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -280,6 +280,9 @@ void __ref xen_build_mfn_list_list(void)
 {
        unsigned long pfn;
 
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               return;
+
        /* Pre-initialize p2m_top_mfn to be completely missing */
        if (p2m_top_mfn == NULL) {
                p2m_mid_missing_mfn = extend_brk(PAGE_SIZE, PAGE_SIZE);
@@ -346,10 +349,15 @@ void xen_setup_mfn_list_list(void)
 /* Set up p2m_top to point to the domain-builder provided p2m pages */
 void __init xen_build_dynamic_phys_to_machine(void)
 {
-       unsigned long *mfn_list = (unsigned long *)xen_start_info->mfn_list;
-       unsigned long max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
+       unsigned long *mfn_list;
+       unsigned long max_pfn;
        unsigned long pfn;
 
+        if (xen_feature(XENFEAT_auto_translated_physmap))
+               return;
+
+       mfn_list = (unsigned long *)xen_start_info->mfn_list;
+       max_pfn = min(MAX_DOMAIN_PAGES, xen_start_info->nr_pages);
        xen_max_p2m_pfn = max_pfn;
 
        p2m_missing = extend_brk(PAGE_SIZE, PAGE_SIZE);
-- 
1.8.3.1


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