The first change is simply addressing a build issue noticed by
Andrew. The build breakage goes beyond this specific combination
though - PV_SHIM_EXCLUSIVE plus HVM is similarly an issue. This
is what the last patch tries to take care of, in a shape already
on irc noticed to be controversial. I'm submitting the change
nevertheless because for the moment there looks to be a majority
in favor of going this route. One argument not voiced there yet:
What good does it do to allow a user to enable HVM when then on
the resulting hypervisor they still can't run HVM guests (for
the hypervisor still being a dedicated PV shim one). On top of
this, the alternative approach is likely going to get ugly.

1: fix build with PV_SHIM_EXCLUSIVE and SHADOW_PAGING
2: adjust Kconfig defaults
3: don't permit HVM and PV_SHIM_EXCLUSIVE at the same time

Jan

While there's little point in enabling both, the combination ought to at
least build correctly. Drop the direct PV_SHIM_EXCLUSIVE conditionals
and instead zap PG_log_dirty to zero under the right conditions, and key
other #ifdef-s off of that.

While there also expand on ded576ce07e9 ("x86/shadow: dirty VRAM
tracking is needed for HVM only"): There was yet another is_hvm_domain()
missing, and code touching the struct fields needs to be guarded by
suitable #ifdef-s as well. While there also guard shadow-mode-only
fields accordingly.

Fixes: 8b5b49ceb3d9 ("x86: don't include domctl and alike in shim-exclusive builds")
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/mm/paging.c
+++ b/xen/arch/x86/mm/paging.c
@@ -47,7 +47,7 @@
 /* Per-CPU variable for enforcing the lock ordering */
 DEFINE_PER_CPU(int, mm_lock_level);
 
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#if PG_log_dirty
 
 /************************************************/
 /*              LOG DIRTY SUPPORT               */
@@ -630,7 +630,7 @@ void paging_log_dirty_init(struct domain
     d->arch.paging.log_dirty.ops = ops;
 }
 
-#endif /* CONFIG_PV_SHIM_EXCLUSIVE */
+#endif /* PG_log_dirty */
 
 /************************************************/
 /*           CODE FOR PAGING SUPPORT            */
@@ -671,7 +671,7 @@ void paging_vcpu_init(struct vcpu *v)
         shadow_vcpu_init(v);
 }
 
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#if PG_log_dirty
 int paging_domctl(struct domain *d, struct xen_domctl_shadow_op *sc,
                   XEN_GUEST_HANDLE_PARAM(xen_domctl_t) u_domctl,
                   bool_t resuming)
@@ -792,7 +792,7 @@ long paging_domctl_continuation(XEN_GUES
 
     return ret;
 }
-#endif /* CONFIG_PV_SHIM_EXCLUSIVE */
+#endif /* PG_log_dirty */
 
 /* Call when destroying a domain */
 int paging_teardown(struct domain *d)
@@ -808,7 +808,7 @@ int paging_teardown(struct domain *d)
     if ( preempted )
         return -ERESTART;
 
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#if PG_log_dirty
     /* clean up log dirty resources. */
     rc = paging_free_log_dirty_bitmap(d, 0);
     if ( rc == -ERESTART )
--- a/xen/arch/x86/mm/shadow/common.c
+++ b/xen/arch/x86/mm/shadow/common.c
@@ -2869,12 +2869,14 @@ void shadow_teardown(struct domain *d, b
      * calls now that we've torn down the bitmap */
     d->arch.paging.mode &= ~PG_log_dirty;
 
-    if ( d->arch.hvm.dirty_vram )
+#ifdef CONFIG_HVM
+    if ( is_hvm_domain(d) && d->arch.hvm.dirty_vram )
     {
         xfree(d->arch.hvm.dirty_vram->sl1ma);
         xfree(d->arch.hvm.dirty_vram->dirty_bitmap);
         XFREE(d->arch.hvm.dirty_vram);
     }
+#endif
 
 out:
     paging_unlock(d);
--- a/xen/arch/x86/mm/shadow/multi.c
+++ b/xen/arch/x86/mm/shadow/multi.c
@@ -618,6 +618,7 @@ _sh_propagate(struct vcpu *v,
         }
     }
 
+#ifdef CONFIG_HVM
     if ( unlikely(level == 1) && is_hvm_domain(d) )
     {
         struct sh_dirty_vram *dirty_vram = d->arch.hvm.dirty_vram;
@@ -632,6 +633,7 @@ _sh_propagate(struct vcpu *v,
                 sflags &= ~_PAGE_RW;
         }
     }
+#endif
 
     /* Read-only memory */
     if ( p2m_is_readonly(p2mt) )
@@ -1050,6 +1052,7 @@ static inline void shadow_vram_get_l1e(s
                                        mfn_t sl1mfn,
                                        struct domain *d)
 {
+#ifdef CONFIG_HVM
     mfn_t mfn = shadow_l1e_get_mfn(new_sl1e);
     int flags = shadow_l1e_get_flags(new_sl1e);
     unsigned long gfn;
@@ -1074,6 +1077,7 @@ static inline void shadow_vram_get_l1e(s
             dirty_vram->sl1ma[i] = mfn_to_maddr(sl1mfn)
                 | ((unsigned long)sl1e & ~PAGE_MASK);
     }
+#endif
 }
 
 static inline void shadow_vram_put_l1e(shadow_l1e_t old_sl1e,
@@ -1081,6 +1085,7 @@ static inline void shadow_vram_put_l1e(s
                                        mfn_t sl1mfn,
                                        struct domain *d)
 {
+#ifdef CONFIG_HVM
     mfn_t mfn = shadow_l1e_get_mfn(old_sl1e);
     int flags = shadow_l1e_get_flags(old_sl1e);
     unsigned long gfn;
@@ -1140,6 +1145,7 @@ static inline void shadow_vram_put_l1e(s
             dirty_vram->last_dirty = NOW();
         }
     }
+#endif
 }
 
 static int shadow_set_l1e(struct domain *d,
--- a/xen/include/asm-x86/paging.h
+++ b/xen/include/asm-x86/paging.h
@@ -67,8 +67,12 @@
 #define PG_translate   0
 #define PG_external    0
 #endif
+#if defined(CONFIG_HVM) || !defined(CONFIG_PV_SHIM_EXCLUSIVE)
 /* Enable log dirty mode */
 #define PG_log_dirty   (XEN_DOMCTL_SHADOW_ENABLE_LOG_DIRTY << PG_mode_shift)
+#else
+#define PG_log_dirty   0
+#endif
 
 /* All paging modes. */
 #define PG_MASK (PG_refcounts | PG_log_dirty | PG_translate | PG_external)
@@ -154,7 +158,7 @@ struct paging_mode {
 /*****************************************************************************
  * Log dirty code */
 
-#ifndef CONFIG_PV_SHIM_EXCLUSIVE
+#if PG_log_dirty
 
 /* get the dirty bitmap for a specific range of pfns */
 void paging_log_dirty_range(struct domain *d,
@@ -195,23 +199,28 @@ int paging_mfn_is_dirty(struct domain *d
 #define L4_LOGDIRTY_IDX(pfn) ((pfn_x(pfn) >> (PAGE_SHIFT + 3 + PAGETABLE_ORDER * 2)) & \
                               (LOGDIRTY_NODE_ENTRIES-1))
 
+#ifdef CONFIG_HVM
 /* VRAM dirty tracking support */
 struct sh_dirty_vram {
     unsigned long begin_pfn;
     unsigned long end_pfn;
+#ifdef CONFIG_SHADOW_PAGING
     paddr_t *sl1ma;
     uint8_t *dirty_bitmap;
     s_time_t last_dirty;
+#endif
 };
+#endif
 
-#else /* !CONFIG_PV_SHIM_EXCLUSIVE */
+#else /* !PG_log_dirty */
 
 static inline void paging_log_dirty_init(struct domain *d,
                                          const struct log_dirty_ops *ops) {}
 static inline void paging_mark_dirty(struct domain *d, mfn_t gmfn) {}
 static inline void paging_mark_pfn_dirty(struct domain *d, pfn_t pfn) {}
+static inline bool paging_mfn_is_dirty(struct domain *d, mfn_t gmfn) { return false; }
 
-#endif /* CONFIG_PV_SHIM_EXCLUSIVE */
+#endif /* PG_log_dirty */
 
 /*****************************************************************************
  * Entry points into the paging-assistance code */

Just like HVM, defaulting SHADOW_PAGING and TBOOT to Yes in shim-
exclusive mode makes no sense, as the respective code is dead there.

Also adjust the shim default config file: It needs to specifiy values
only for settings where a non-default value is wanted.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -116,9 +116,9 @@ config XEN_SHSTK
 	  compatiblity can be provided via the PV Shim mechanism.
 
 config SHADOW_PAGING
-        bool "Shadow Paging"
-        default y
-        ---help---
+	bool "Shadow Paging"
+	default y if !PV_SHIM_EXCLUSIVE
+	---help---
 
           Shadow paging is a software alternative to hardware paging support
           (Intel EPT, AMD NPT).
@@ -165,8 +165,8 @@ config HVM_FEP
 	  If unsure, say N.
 
 config TBOOT
-	def_bool y
-	prompt "Xen tboot support" if EXPERT
+	bool "Xen tboot support" if EXPERT
+	default y if !PV_SHIM_EXCLUSIVE
 	select CRYPTO
 	---help---
 	  Allows support for Trusted Boot using the Intel(R) Trusted Execution
--- a/xen/arch/x86/configs/pvshim_defconfig
+++ b/xen/arch/x86/configs/pvshim_defconfig
@@ -8,12 +8,9 @@ CONFIG_NR_CPUS=32
 CONFIG_EXPERT=y
 CONFIG_SCHED_NULL=y
 # Disable features not used by the PV shim
-# CONFIG_HVM is not set
 # CONFIG_XEN_SHSTK is not set
 # CONFIG_HYPFS is not set
-# CONFIG_SHADOW_PAGING is not set
 # CONFIG_BIGMEM is not set
-# CONFIG_TBOOT is not set
 # CONFIG_KEXEC is not set
 # CONFIG_XENOPROF is not set
 # CONFIG_XSM is not set

This combination doesn't really make sense (and there likely are more).
The alternative here would be some presumably intrusive #ifdef-ary to
get this combination to actually build again.

Signed-off-by: Jan Beulich <jbeulich@suse.com>

--- a/xen/arch/x86/Kconfig
+++ b/xen/arch/x86/Kconfig
@@ -23,7 +23,7 @@ config X86
 	select HAS_PDX
 	select HAS_SCHED_GRANULARITY
 	select HAS_UBSAN
-	select HAS_VPCI if !PV_SHIM_EXCLUSIVE && HVM
+	select HAS_VPCI if HVM
 	select NEEDS_LIBELF
 	select NUMA
 
@@ -90,8 +90,8 @@ config PV_LINEAR_PT
          If unsure, say Y.
 
 config HVM
-	def_bool !PV_SHIM_EXCLUSIVE
-	prompt "HVM support"
+	bool "HVM support"
+	depends on !PV_SHIM_EXCLUSIVE
 	---help---
 	  Interfaces to support HVM domains.  HVM domains require hardware
 	  virtualisation extensions (e.g. Intel VT-x, AMD SVM), but can boot