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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v4 3/7] xen/x86: support per-domain flag for xpti
Instead of switching XPTI globally on or off add a per-domain flag for
that purpose. This allows to modify the xpti boot parameter to support
running dom0 without Meltdown mitigations. Using "xpti=nodom0" as boot
parameter will achieve that.
Move the xpti boot parameter handling to xen/arch/x86/pv/domain.c as
it is pv-domain specific.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
---
V3:
- latch get_cpu_info() return value in variable (Jan Beulich)
- call always xpti_domain_init() for pv dom0 (Jan Beulich)
- add __init annotations (Jan Beulich)
- drop per domain XPTI message (Jan Beulich)
- document xpti=default support (Jan Beulich)
- move domain xpti flag into a padding hole (Jan Beulich)
---
docs/misc/xen-command-line.markdown | 10 ++++-
xen/arch/x86/domctl.c | 4 ++
xen/arch/x86/mm.c | 12 +++++-
xen/arch/x86/pv/dom0_build.c | 3 ++
xen/arch/x86/pv/domain.c | 79 ++++++++++++++++++++++++++++++++++++-
xen/arch/x86/setup.c | 20 +---------
xen/arch/x86/smpboot.c | 4 +-
xen/arch/x86/x86_64/entry.S | 2 +
xen/include/asm-x86/current.h | 3 +-
xen/include/asm-x86/domain.h | 3 ++
xen/include/asm-x86/pv/domain.h | 4 ++
11 files changed, 119 insertions(+), 25 deletions(-)
diff --git a/docs/misc/xen-command-line.markdown
b/docs/misc/xen-command-line.markdown
index b353352adf..79be9a6ba5 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1955,7 +1955,7 @@ clustered mode. The default, given no hint from the
**FADT**, is cluster
mode.
### xpti
-> `= <boolean>`
+> `= default | nodom0 | <boolean>`
> Default: `false` on AMD hardware
> Default: `true` everywhere else
@@ -1963,6 +1963,14 @@ mode.
Override default selection of whether to isolate 64-bit PV guest page
tables.
+`true` activates page table isolation even on AMD hardware.
+
+`false` deactivates page table isolation on all systems.
+
+`default` sets the default behaviour.
+
+`nodom0` deactivates page table isolation for dom0.
+
### xsave
> `= <boolean>`
diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
index 8fbbf3aeb3..0704f398c7 100644
--- a/xen/arch/x86/domctl.c
+++ b/xen/arch/x86/domctl.c
@@ -24,6 +24,7 @@
#include <asm/hvm/hvm.h>
#include <asm/hvm/support.h>
#include <asm/processor.h>
+#include <asm/pv/domain.h>
#include <asm/acpi.h> /* for hvm_acpi_power_button */
#include <xen/hypercall.h> /* for arch_do_domctl */
#include <xsm/xsm.h>
@@ -610,6 +611,9 @@ long arch_do_domctl(
ret = switch_compat(d);
else
ret = -EINVAL;
+
+ if ( ret == 0 )
+ xpti_domain_init(d);
break;
case XEN_DOMCTL_get_address_size:
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index f7d24a1f8b..008dcc1749 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -504,13 +504,21 @@ void make_cr3(struct vcpu *v, mfn_t mfn)
void write_ptbase(struct vcpu *v)
{
- if ( this_cpu(root_pgt) && is_pv_vcpu(v) && !is_pv_32bit_vcpu(v) )
+ struct cpu_info *cpu_info = get_cpu_info();
+
+ if ( is_pv_vcpu(v) && v->domain->arch.pv_domain.xpti )
{
- get_cpu_info()->root_pgt_changed = true;
+ cpu_info->root_pgt_changed = true;
+ cpu_info->pv_cr3 = __pa(this_cpu(root_pgt));
asm volatile ( "mov %0, %%cr3" : : "r" (v->arch.cr3) : "memory" );
}
else
+ {
+ /* Make sure to clear xen_cr3 before pv_cr3; write_cr3() serializes. */
+ cpu_info->xen_cr3 = 0;
write_cr3(v->arch.cr3);
+ cpu_info->pv_cr3 = 0;
+ }
}
/*
diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
index 0bd2f1bf90..77186c19bd 100644
--- a/xen/arch/x86/pv/dom0_build.c
+++ b/xen/arch/x86/pv/dom0_build.c
@@ -19,6 +19,7 @@
#include <asm/dom0_build.h>
#include <asm/guest.h>
#include <asm/page.h>
+#include <asm/pv/domain.h>
#include <asm/pv/mm.h>
#include <asm/setup.h>
@@ -707,6 +708,8 @@ int __init dom0_construct_pv(struct domain *d,
cpu = p->processor;
}
+ xpti_domain_init(d);
+
d->arch.paging.mode = 0;
/* Set up CR3 value for write_ptbase */
diff --git a/xen/arch/x86/pv/domain.c b/xen/arch/x86/pv/domain.c
index fd529332a3..e6bb2bac76 100644
--- a/xen/arch/x86/pv/domain.c
+++ b/xen/arch/x86/pv/domain.c
@@ -9,6 +9,8 @@
#include <xen/lib.h>
#include <xen/sched.h>
+#include <asm/cpufeature.h>
+#include <asm/msr-index.h>
#include <asm/pv/domain.h>
/* Override macros from asm/page.h to make them work with mfn_t */
@@ -17,6 +19,81 @@
#undef page_to_mfn
#define page_to_mfn(pg) _mfn(__page_to_mfn(pg))
+static __read_mostly enum {
+ XPTI_DEFAULT,
+ XPTI_ON,
+ XPTI_OFF,
+ XPTI_NODOM0
+} opt_xpti = XPTI_DEFAULT;
+
+static __init int parse_xpti(const char *s)
+{
+ int rc = 0;
+
+ switch ( parse_bool(s, NULL) )
+ {
+ case 0:
+ opt_xpti = XPTI_OFF;
+ break;
+ case 1:
+ opt_xpti = XPTI_ON;
+ break;
+ default:
+ if ( !strcmp(s, "default") )
+ opt_xpti = XPTI_DEFAULT;
+ else if ( !strcmp(s, "nodom0") )
+ opt_xpti = XPTI_NODOM0;
+ else
+ rc = -EINVAL;
+ break;
+ }
+
+ return rc;
+}
+custom_param("xpti", parse_xpti);
+
+void __init xpti_init(void)
+{
+ uint64_t caps = 0;
+
+ if ( boot_cpu_data.x86_vendor == X86_VENDOR_AMD )
+ caps = ARCH_CAPABILITIES_RDCL_NO;
+ else if ( boot_cpu_has(X86_FEATURE_ARCH_CAPS) )
+ rdmsrl(MSR_ARCH_CAPABILITIES, caps);
+
+ if ( opt_xpti != XPTI_ON && (caps & ARCH_CAPABILITIES_RDCL_NO) )
+ opt_xpti = XPTI_OFF;
+ else if ( opt_xpti == XPTI_DEFAULT )
+ opt_xpti = XPTI_ON;
+
+ if ( opt_xpti == XPTI_OFF )
+ setup_force_cpu_cap(X86_FEATURE_NO_XPTI);
+ else
+ setup_clear_cpu_cap(X86_FEATURE_NO_XPTI);
+}
+
+void xpti_domain_init(struct domain *d)
+{
+ if ( !is_pv_domain(d) || is_pv_32bit_domain(d) )
+ return;
+
+ switch ( opt_xpti )
+ {
+ case XPTI_OFF:
+ break;
+ case XPTI_ON:
+ d->arch.pv_domain.xpti = true;
+ break;
+ case XPTI_NODOM0:
+ d->arch.pv_domain.xpti = d->domain_id != 0 &&
+ d->domain_id != hardware_domid;
+ break;
+ default:
+ ASSERT_UNREACHABLE();
+ break;
+ }
+}
+
static void noreturn continue_nonidle_domain(struct vcpu *v)
{
check_wakeup_from_wait();
@@ -265,7 +342,7 @@ void toggle_guest_mode(struct vcpu *v)
}
asm volatile ( "swapgs" );
- _toggle_guest_pt(v, cpu_has_no_xpti);
+ _toggle_guest_pt(v, !v->domain->arch.pv_domain.xpti);
}
void toggle_guest_pt(struct vcpu *v)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 9591fd987b..33bb05b5d7 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -53,6 +53,7 @@
#include <asm/cpuid.h>
#include <asm/spec_ctrl.h>
#include <asm/guest.h>
+#include <asm/pv/domain.h>
/* opt_nosmp: If true, secondary processors are ignored. */
static bool __initdata opt_nosmp;
@@ -169,9 +170,6 @@ static int __init parse_smap_param(const char *s)
}
custom_param("smap", parse_smap_param);
-static int8_t __initdata opt_xpti = -1;
-boolean_param("xpti", opt_xpti);
-
bool __read_mostly acpi_disabled;
bool __initdata acpi_force;
static char __initdata acpi_param[10] = "";
@@ -1546,21 +1544,7 @@ void __init noreturn __start_xen(unsigned long mbi_p)
cr4_pv32_mask = mmu_cr4_features & XEN_CR4_PV32_BITS;
- if ( opt_xpti < 0 )
- {
- uint64_t caps = 0;
-
- if ( boot_cpu_data.x86_vendor == X86_VENDOR_AMD )
- caps = ARCH_CAPABILITIES_RDCL_NO;
- else if ( boot_cpu_has(X86_FEATURE_ARCH_CAPS) )
- rdmsrl(MSR_ARCH_CAPABILITIES, caps);
-
- opt_xpti = !(caps & ARCH_CAPABILITIES_RDCL_NO);
- }
- if ( opt_xpti )
- setup_clear_cpu_cap(X86_FEATURE_NO_XPTI);
- else
- setup_force_cpu_cap(X86_FEATURE_NO_XPTI);
+ xpti_init();
if ( cpu_has_fsgsbase )
set_in_cr4(X86_CR4_FSGSBASE);
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index b0b72ca544..346a8e8a3f 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -331,7 +331,7 @@ void start_secondary(void *unused)
spin_debug_disable();
get_cpu_info()->xen_cr3 = 0;
- get_cpu_info()->pv_cr3 = this_cpu(root_pgt) ? __pa(this_cpu(root_pgt)) : 0;
+ get_cpu_info()->pv_cr3 = 0;
load_system_tables();
@@ -1050,7 +1050,7 @@ void __init smp_prepare_cpus(unsigned int max_cpus)
panic("Error %d setting up PV root page table\n", rc);
if ( per_cpu(root_pgt, 0) )
{
- get_cpu_info()->pv_cr3 = __pa(per_cpu(root_pgt, 0));
+ get_cpu_info()->pv_cr3 = 0;
/*
* All entry points which may need to switch page tables have to start
diff --git a/xen/arch/x86/x86_64/entry.S b/xen/arch/x86/x86_64/entry.S
index 18b79be539..2a06cd1a51 100644
--- a/xen/arch/x86/x86_64/entry.S
+++ b/xen/arch/x86/x86_64/entry.S
@@ -130,6 +130,8 @@ restore_all_guest:
mov VCPU_cr3(%rbx), %r9
GET_STACK_END(dx)
mov STACK_CPUINFO_FIELD(pv_cr3)(%rdx), %rax
+ test %rax, %rax
+ jz .Lrag_cr3_end
cmpb $0, STACK_CPUINFO_FIELD(root_pgt_changed)(%rdx)
je .Lrag_copy_done
movb $0, STACK_CPUINFO_FIELD(root_pgt_changed)(%rdx)
diff --git a/xen/include/asm-x86/current.h b/xen/include/asm-x86/current.h
index f2491b4423..b2475783f8 100644
--- a/xen/include/asm-x86/current.h
+++ b/xen/include/asm-x86/current.h
@@ -44,7 +44,8 @@ struct cpu_info {
/*
* Of the two following fields the latter is being set to the CR3 value
* to be used on the given pCPU for loading whenever 64-bit PV guest
- * context is being entered. The value never changes once set.
+ * context is being entered. A value of zero indicates no setting of CR3
+ * is to be performed.
* The former is the value to restore when re-entering Xen, if any. IOW
* its value being zero means there's nothing to restore. However, its
* value can also be negative, indicating to the exit-to-Xen code that
diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
index a12ae47f1b..ed4199931a 100644
--- a/xen/include/asm-x86/domain.h
+++ b/xen/include/asm-x86/domain.h
@@ -253,6 +253,9 @@ struct pv_domain
atomic_t nr_l4_pages;
+ /* XPTI active? */
+ bool xpti;
+
/* map_domain_page() mapping cache. */
struct mapcache_domain mapcache;
diff --git a/xen/include/asm-x86/pv/domain.h b/xen/include/asm-x86/pv/domain.h
index 5e34176939..911e5dc07f 100644
--- a/xen/include/asm-x86/pv/domain.h
+++ b/xen/include/asm-x86/pv/domain.h
@@ -27,6 +27,8 @@ void pv_vcpu_destroy(struct vcpu *v);
int pv_vcpu_initialise(struct vcpu *v);
void pv_domain_destroy(struct domain *d);
int pv_domain_initialise(struct domain *d);
+void xpti_init(void);
+void xpti_domain_init(struct domain *d);
#else /* !CONFIG_PV */
@@ -36,6 +38,8 @@ static inline void pv_vcpu_destroy(struct vcpu *v) {}
static inline int pv_vcpu_initialise(struct vcpu *v) { return -EOPNOTSUPP; }
static inline void pv_domain_destroy(struct domain *d) {}
static inline int pv_domain_initialise(struct domain *d) { return -EOPNOTSUPP;
}
+static inline void xpti_init(void) {}
+static inline void xpti_domain_init(struct domain *d) {}
#endif /* CONFIG_PV */
--
2.13.6
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