x86: clarify shadow paging Dom0 support

Classic PV shadow paging Dom0 has been broken for years, and can't
possibly be configured after 4045953.

PVH shadow paging Dom0 should still be possible.

Change the code and documentation to clarify that.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Andrew Cooper <andrew.cooper@citrix.com>

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index bdbdb8a53beab37a24727a594477219f9c287397..9eb85d68b59b1c0f330e8296117dcc9433d2c216 100644 (file)
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -652,11 +652,6 @@ restrictions set up here. Note that the values to be specified here are
 ACPI PXM ones, not Xen internal node numbers. `relaxed` sets up vCPU
 affinities to prefer but be not limited to the specified node(s).
 
-### dom0\_shadow
-> `= <boolean>`
-
-This option is deprecated, please use `dom0=shadow` instead.
-
 ### dom0\_vcpus\_pin
 > `= <boolean>`
 
@@ -679,7 +674,8 @@ Flag that makes a dom0 boot in PVHv2 mode.
 
 > Default: `false`
 
-Flag that makes a dom0 use shadow paging.
+Flag that makes a dom0 use shadow paging. Only works when "pvh" is
+enabled.
 
 ### dtuart (ARM)
 > `= path [:options]`

diff --git a/xen/arch/x86/dom0_build.c b/xen/arch/x86/dom0_build.c
index 20221b5e3287d8247cee66ce1b1457791cf7d795..cc8acad688d6aed32749574a91bf1ed37554dfcd 100644 (file)
--- a/xen/arch/x86/dom0_build.c
+++ b/xen/arch/x86/dom0_build.c
@@ -174,7 +174,6 @@ struct vcpu *__init alloc_dom0_vcpu0(struct domain *dom0)
 
 #ifdef CONFIG_SHADOW_PAGING
 bool __initdata opt_dom0_shadow;
-boolean_param("dom0_shadow", opt_dom0_shadow);
 #endif
 bool __initdata dom0_pvh;
 
@@ -252,8 +251,8 @@ unsigned long __init dom0_compute_nr_pages(
             avail -= max_pdx >> s;
     }
 
-    need_paging = is_hvm_domain(d) ? !iommu_hap_pt_share || !paging_mode_hap(d)
-                                   : opt_dom0_shadow;
+    need_paging = is_hvm_domain(d) &&
+        (!iommu_hap_pt_share || !paging_mode_hap(d));
     for ( ; ; need_paging = 0 )
     {
         nr_pages = dom0_nrpages;
@@ -456,6 +455,14 @@ int __init construct_dom0(struct domain *d, const module_t *image,
 
     process_pending_softirqs();
 
+#ifdef CONFIG_SHADOW_PAGING
+    if ( opt_dom0_shadow && !dom0_pvh )
+    {
+        opt_dom0_shadow = false;
+        printk(XENLOG_WARNING "Shadow Dom0 requires PVH. Option ignored.\n");
+    }
+#endif
+
     return (is_hvm_domain(d) ? dom0_construct_pvh : dom0_construct_pv)
            (d, image, image_headroom, initrd,bootstrap_map, cmdline);
 }

diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index 65cd2c5019b3d47a9f5409aa478faaac83f07187..18c19a256f507cbebac024d987dbdc443a373131 100644 (file)
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -870,11 +870,6 @@ int __init dom0_construct_pv(struct domain *d,
     regs->rsi = vstartinfo_start;
     regs->eflags = X86_EFLAGS_IF;
 
-#ifdef CONFIG_SHADOW_PAGING
-    if ( opt_dom0_shadow && paging_enable(d, PG_SH_enable) == 0 )
-        paging_update_paging_modes(v);
-#endif
-
     if ( test_bit(XENFEAT_supervisor_mode_kernel, parms.f_required) )
         panic("Dom0 requires supervisor-mode execution");