xen/pvshim: modify Dom0 builder in order to build a DomU

According to the PV ABI the initial virtual memory regions should
contain the xenstore and console pages after the start_info. Also set
the correct values in the start_info for DomU operation.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
---
Changes since v1:
 - Modify the position of the __init attribute in dom0_update_physmap.
 - Move the addition of sizeof(struct dom0_vga_console_info) to
   vstartinfo_end with an existing if branch.
 - Add a TODO item for fill_console_start_info in the !CONFIG_VIDEO
   case.
 - s/replace_va/replace_va_mapping/.
 - Remove call to free_domheap_pages in replace_va_mapping.
   put_page_and_type should already take care of freeing the page.
 - Use PFN_DOWN in SET_AND_MAP_PARAM macro.
 - Parenthesize va in SET_AND_MAP_PARAM macro when required.

4 files changed, 126 insertions, 10 deletions

diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index 852d00a8be..72752b8656 100644
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -31,9 +31,8 @@
 #define L3_PROT (BASE_PROT|_PAGE_DIRTY)
 #define L4_PROT (BASE_PROT|_PAGE_DIRTY)
 
-static __init void dom0_update_physmap(struct domain *d, unsigned long pfn,
-                                       unsigned long mfn,
-                                       unsigned long vphysmap_s)
+void __init dom0_update_physmap(struct domain *d, unsigned long pfn,
+                                unsigned long mfn, unsigned long vphysmap_s)
 {
     if ( !is_pv_32bit_domain(d) )
         ((unsigned long *)vphysmap_s)[pfn] = mfn;
@@ -316,6 +315,10 @@ int __init dom0_construct_pv(struct domain *d,
     unsigned long vphysmap_end;
     unsigned long vstartinfo_start;
     unsigned long vstartinfo_end;
+    unsigned long vxenstore_start = 0;
+    unsigned long vxenstore_end = 0;
+    unsigned long vconsole_start = 0;
+    unsigned long vconsole_end = 0;
     unsigned long vstack_start;
     unsigned long vstack_end;
     unsigned long vpt_start;
@@ -441,11 +444,22 @@ int __init dom0_construct_pv(struct domain *d,
     if ( parms.p2m_base != UNSET_ADDR )
         vphysmap_end = vphysmap_start;
     vstartinfo_start = round_pgup(vphysmap_end);
-    vstartinfo_end   = (vstartinfo_start +
-                        sizeof(struct start_info) +
-                        sizeof(struct dom0_vga_console_info));
+    vstartinfo_end   = vstartinfo_start + sizeof(struct start_info);
+
+    if ( pv_shim )
+    {
+        vxenstore_start  = round_pgup(vstartinfo_end);
+        vxenstore_end    = vxenstore_start + PAGE_SIZE;
+        vconsole_start   = vxenstore_end;
+        vconsole_end     = vconsole_start + PAGE_SIZE;
+        vpt_start        = vconsole_end;
+    }
+    else
+    {
+        vpt_start        = round_pgup(vstartinfo_end);
+        vstartinfo_end  += sizeof(struct dom0_vga_console_info);
+    }
 
-    vpt_start        = round_pgup(vstartinfo_end);
     for ( nr_pt_pages = 2; ; nr_pt_pages++ )
     {
         vpt_end          = vpt_start + (nr_pt_pages * PAGE_SIZE);
@@ -538,6 +552,8 @@ int __init dom0_construct_pv(struct domain *d,
            " Init. ramdisk: %p->%p\n"
            " Phys-Mach map: %p->%p\n"
            " Start info:    %p->%p\n"
+           " Xenstore ring: %p->%p\n"
+           " Console ring:  %p->%p\n"
            " Page tables:   %p->%p\n"
            " Boot stack:    %p->%p\n"
            " TOTAL:         %p->%p\n",
@@ -545,6 +561,8 @@ int __init dom0_construct_pv(struct domain *d,
            _p(vinitrd_start), _p(vinitrd_end),
            _p(vphysmap_start), _p(vphysmap_end),
            _p(vstartinfo_start), _p(vstartinfo_end),
+           _p(vxenstore_start), _p(vxenstore_end),
+           _p(vconsole_start), _p(vconsole_end),
            _p(vpt_start), _p(vpt_end),
            _p(vstack_start), _p(vstack_end),
            _p(v_start), _p(v_end));
@@ -742,7 +760,8 @@ int __init dom0_construct_pv(struct domain *d,
 
     si->shared_info = virt_to_maddr(d->shared_info);
 
-    si->flags        = SIF_PRIVILEGED | SIF_INITDOMAIN;
+    if ( !pv_shim )
+        si->flags    = SIF_PRIVILEGED | SIF_INITDOMAIN;
     if ( !vinitrd_start && initrd_len )
         si->flags   |= SIF_MOD_START_PFN;
     si->flags       |= (xen_processor_pmbits << 8) & SIF_PM_MASK;
@@ -834,15 +853,24 @@ int __init dom0_construct_pv(struct domain *d,
         strlcpy((char *)si->cmd_line, cmdline, sizeof(si->cmd_line));
 
 #ifdef CONFIG_VIDEO
-    if ( fill_console_start_info((void *)(si + 1)) )
+    if ( !pv_shim && fill_console_start_info((void *)(si + 1)) )
     {
         si->console.dom0.info_off  = sizeof(struct start_info);
         si->console.dom0.info_size = sizeof(struct dom0_vga_console_info);
     }
 #endif
 
+    /*
+     * TODO: provide an empty stub for fill_console_start_info in the
+     * !CONFIG_VIDEO case so the logic here can be simplified.
+     */
+    if ( pv_shim )
+        pv_shim_setup_dom(d, l4start, v_start, vxenstore_start, vconsole_start,
+                          vphysmap_start, si);
+
     if ( is_pv_32bit_domain(d) )
-        xlat_start_info(si, XLAT_start_info_console_dom0);
+        xlat_start_info(si, pv_shim ? XLAT_start_info_console_domU
+                                    : XLAT_start_info_console_dom0);
 
     /* Return to idle domain's page tables. */
     mapcache_override_current(NULL);
diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index 4d037355db..75365b0697 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -18,16 +18,79 @@
  *
  * Copyright (c) 2017 Citrix Systems Ltd.
  */
+#include <xen/hypercall.h>
 #include <xen/init.h>
 #include <xen/types.h>
 
 #include <asm/apic.h>
+#include <asm/dom0_build.h>
+#include <asm/guest.h>
+#include <asm/pv/mm.h>
 
 #ifndef CONFIG_PV_SHIM_EXCLUSIVE
 bool pv_shim;
 boolean_param("pv-shim", pv_shim);
 #endif
 
+#define L1_PROT (_PAGE_PRESENT|_PAGE_RW|_PAGE_ACCESSED|_PAGE_USER| \
+                 _PAGE_GUEST_KERNEL)
+#define COMPAT_L1_PROT (_PAGE_PRESENT|_PAGE_RW|_PAGE_ACCESSED)
+
+static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
+                                      unsigned long va, unsigned long mfn)
+{
+    struct page_info *page;
+    l4_pgentry_t *pl4e;
+    l3_pgentry_t *pl3e;
+    l2_pgentry_t *pl2e;
+    l1_pgentry_t *pl1e;
+
+    pl4e = l4start + l4_table_offset(va);
+    pl3e = l4e_to_l3e(*pl4e);
+    pl3e += l3_table_offset(va);
+    pl2e = l3e_to_l2e(*pl3e);
+    pl2e += l2_table_offset(va);
+    pl1e = l2e_to_l1e(*pl2e);
+    pl1e += l1_table_offset(va);
+
+    page = mfn_to_page(l1e_get_pfn(*pl1e));
+    put_page_and_type(page);
+
+    *pl1e = l1e_from_pfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
+                                                      : COMPAT_L1_PROT));
+}
+
+void __init pv_shim_setup_dom(struct domain *d, l4_pgentry_t *l4start,
+                              unsigned long va_start, unsigned long store_va,
+                              unsigned long console_va, unsigned long vphysmap,
+                              start_info_t *si)
+{
+    uint64_t param = 0;
+    long rc;
+
+#define SET_AND_MAP_PARAM(p, si, va) ({                                        \
+    rc = xen_hypercall_hvm_get_param(p, &param);                               \
+    if ( rc )                                                                  \
+        panic("Unable to get " #p "\n");                                       \
+    (si) = param;                                                              \
+    if ( va )                                                                  \
+    {                                                                          \
+        share_xen_page_with_guest(mfn_to_page(param), d, XENSHARE_writable);   \
+        replace_va_mapping(d, l4start, va, param);                             \
+        dom0_update_physmap(d, PFN_DOWN((va) - va_start), param, vphysmap);    \
+    }                                                                          \
+})
+    SET_AND_MAP_PARAM(HVM_PARAM_STORE_PFN, si->store_mfn, store_va);
+    SET_AND_MAP_PARAM(HVM_PARAM_STORE_EVTCHN, si->store_evtchn, 0);
+    if ( !pv_console )
+    {
+        SET_AND_MAP_PARAM(HVM_PARAM_CONSOLE_PFN, si->console.domU.mfn,
+                          console_va);
+        SET_AND_MAP_PARAM(HVM_PARAM_CONSOLE_EVTCHN, si->console.domU.evtchn, 0);
+    }
+#undef SET_AND_MAP_PARAM
+}
+
 /*
  * Local variables:
  * mode: C
diff --git a/xen/include/asm-x86/dom0_build.h b/xen/include/asm-x86/dom0_build.h
index d83d2b4387..d985406503 100644
--- a/xen/include/asm-x86/dom0_build.h
+++ b/xen/include/asm-x86/dom0_build.h
@@ -1,6 +1,7 @@
 #ifndef _DOM0_BUILD_H_
 #define _DOM0_BUILD_H_
 
+#include <xen/libelf.h>
 #include <xen/sched.h>
 
 #include <asm/setup.h>
@@ -29,6 +30,9 @@ int dom0_construct_pvh(struct domain *d, const module_t *image,
 unsigned long dom0_paging_pages(const struct domain *d,
                                 unsigned long nr_pages);
 
+void dom0_update_physmap(struct domain *d, unsigned long pfn,
+                         unsigned long mfn, unsigned long vphysmap_s);
+
 #endif	/* _DOM0_BUILD_H_ */
 
 /*
diff --git a/xen/include/asm-x86/pv/shim.h b/xen/include/asm-x86/pv/shim.h
index 1468cfd498..b0c361cba1 100644
--- a/xen/include/asm-x86/pv/shim.h
+++ b/xen/include/asm-x86/pv/shim.h
@@ -29,6 +29,27 @@ extern bool pv_shim;
 # define pv_shim 0
 #endif /* CONFIG_PV_SHIM{,_EXCLUSIVE} */
 
+#ifdef CONFIG_PV_SHIM
+
+void pv_shim_setup_dom(struct domain *d, l4_pgentry_t *l4start,
+                       unsigned long va_start, unsigned long store_va,
+                       unsigned long console_va, unsigned long vphysmap,
+                       start_info_t *si);
+
+#else
+
+static inline void pv_shim_setup_dom(struct domain *d, l4_pgentry_t *l4start,
+                                     unsigned long va_start,
+                                     unsigned long store_va,
+                                     unsigned long console_va,
+                                     unsigned long vphysmap,
+                                     start_info_t *si)
+{
+    ASSERT_UNREACHABLE();
+}
+
+#endif
+
 #endif /* __X86_PV_SHIM_H__ */
 
 /*