[Xen-devel] [PATCH v13 07/19] xen/pvh: MMU changes for PVH (v2)

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

From: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>

.. which are surprinsingly small compared to the amount for PV code.

PVH uses mostly native mmu ops, we leave the generic (native_*) for
the majority and just overwrite the baremetal with the ones we need.

At startup, we are running with pre-allocated page-tables
courtesy of the tool-stack. But we still need to graft them
in the Linux initial pagetables. However there is no need to
unpin/pin and change them to R/O or R/W.

Note that the xen_pagetable_init due to 7836fec9d0994cc9c9150c5a33f0eb0eb08a335a
"xen/mmu/p2m: Refactor the xen_pagetable_init code." does not
need any changes - we just need to make sure that xen_post_allocator_init
does not alter the pvops from the default native one.

Signed-off-by: Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 arch/x86/xen/mmu.c | 81 +++++++++++++++++++++++++++++++-----------------------
 1 file changed, 46 insertions(+), 35 deletions(-)

diff --git a/arch/x86/xen/mmu.c b/arch/x86/xen/mmu.c
index 9d74249..490ddb3 100644
--- a/arch/x86/xen/mmu.c
+++ b/arch/x86/xen/mmu.c
@@ -1757,6 +1757,10 @@ static void set_page_prot_flags(void *addr, pgprot_t 
prot, unsigned long flags)
        unsigned long pfn = __pa(addr) >> PAGE_SHIFT;
        pte_t pte = pfn_pte(pfn, prot);
 
+       /* For PVH no need to set R/O or R/W to pin them or unpin them. */
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               return;
+
        if (HYPERVISOR_update_va_mapping((unsigned long)addr, pte, flags))
                BUG();
 }
@@ -1867,6 +1871,7 @@ static void __init check_pt_base(unsigned long *pt_base, 
unsigned long *pt_end,
  * but that's enough to get __va working.  We need to fill in the rest
  * of the physical mapping once some sort of allocator has been set
  * up.
+ * NOTE: for PVH, the page tables are native.
  */
 void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
 {
@@ -1888,17 +1893,18 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, 
unsigned long max_pfn)
        /* Zap identity mapping */
        init_level4_pgt[0] = __pgd(0);
 
-       /* Pre-constructed entries are in pfn, so convert to mfn */
-       /* L4[272] -> level3_ident_pgt
-        * L4[511] -> level3_kernel_pgt */
-       convert_pfn_mfn(init_level4_pgt);
-
-       /* L3_i[0] -> level2_ident_pgt */
-       convert_pfn_mfn(level3_ident_pgt);
-       /* L3_k[510] -> level2_kernel_pgt
-        * L3_i[511] -> level2_fixmap_pgt */
-       convert_pfn_mfn(level3_kernel_pgt);
-
+       if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+               /* Pre-constructed entries are in pfn, so convert to mfn */
+               /* L4[272] -> level3_ident_pgt
+                * L4[511] -> level3_kernel_pgt */
+               convert_pfn_mfn(init_level4_pgt);
+
+               /* L3_i[0] -> level2_ident_pgt */
+               convert_pfn_mfn(level3_ident_pgt);
+               /* L3_k[510] -> level2_kernel_pgt
+                * L3_i[511] -> level2_fixmap_pgt */
+               convert_pfn_mfn(level3_kernel_pgt);
+       }
        /* We get [511][511] and have Xen's version of level2_kernel_pgt */
        l3 = m2v(pgd[pgd_index(__START_KERNEL_map)].pgd);
        l2 = m2v(l3[pud_index(__START_KERNEL_map)].pud);
@@ -1922,31 +1928,33 @@ void __init xen_setup_kernel_pagetable(pgd_t *pgd, 
unsigned long max_pfn)
        copy_page(level2_fixmap_pgt, l2);
        /* Note that we don't do anything with level1_fixmap_pgt which
         * we don't need. */
+       if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+               /* Make pagetable pieces RO */
+               set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
+               set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
+               set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
+               set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
+               set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
+               set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
+               set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
+
+               /* Pin down new L4 */
+               pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
+                                 PFN_DOWN(__pa_symbol(init_level4_pgt)));
+
+               /* Unpin Xen-provided one */
+               pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
 
-       /* Make pagetable pieces RO */
-       set_page_prot(init_level4_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level3_ident_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level3_kernel_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level3_user_vsyscall, PAGE_KERNEL_RO);
-       set_page_prot(level2_ident_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level2_kernel_pgt, PAGE_KERNEL_RO);
-       set_page_prot(level2_fixmap_pgt, PAGE_KERNEL_RO);
-
-       /* Pin down new L4 */
-       pin_pagetable_pfn(MMUEXT_PIN_L4_TABLE,
-                         PFN_DOWN(__pa_symbol(init_level4_pgt)));
-
-       /* Unpin Xen-provided one */
-       pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
-
-       /*
-        * At this stage there can be no user pgd, and no page
-        * structure to attach it to, so make sure we just set kernel
-        * pgd.
-        */
-       xen_mc_batch();
-       __xen_write_cr3(true, __pa(init_level4_pgt));
-       xen_mc_issue(PARAVIRT_LAZY_CPU);
+               /*
+                * At this stage there can be no user pgd, and no page
+                * structure to attach it to, so make sure we just set kernel
+                * pgd.
+                */
+               xen_mc_batch();
+               __xen_write_cr3(true, __pa(init_level4_pgt));
+               xen_mc_issue(PARAVIRT_LAZY_CPU);
+       } else
+               native_write_cr3(__pa(init_level4_pgt));
 
        /* We can't that easily rip out L3 and L2, as the Xen pagetables are
         * set out this way: [L4], [L1], [L2], [L3], [L1], [L1] ...  for
@@ -2107,6 +2115,9 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t 
phys, pgprot_t prot)
 
 static void __init xen_post_allocator_init(void)
 {
+       if (xen_feature(XENFEAT_auto_translated_physmap))
+               return;
+
        pv_mmu_ops.set_pte = xen_set_pte;
        pv_mmu_ops.set_pmd = xen_set_pmd;
        pv_mmu_ops.set_pud = xen_set_pud;
-- 
1.8.3.1


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