[Xen-changelog] [xen master] x86: check feature flags after resume

[patchbot@xxxxxxx]

commit bb502a8ca59252dfd5a7170cc59321b59ac8c2b7
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Mon Apr 16 14:10:33 2018 +0200
Commit:     Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Mon Apr 16 14:10:33 2018 +0200

    x86: check feature flags after resume
    
    Make sure no previously present features are missing after resume (and
    the re-loading of microcode), to avoid later crashes or (likely silent)
    hangs / live locks. This doesn't go beyond checking x86_capability[],
    but this should be good enough for the immediate need of making sure
    that the BIT mitigation MSRs are still available.
    
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Release-acked-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/arch/x86/acpi/power.c   |  3 +++
 xen/arch/x86/cpu/common.c   |  3 +++
 xen/arch/x86/cpuid.c        | 22 ++++++++++++++++++++++
 xen/arch/x86/smpboot.c      | 18 +++++++++++++++---
 xen/include/asm-x86/cpuid.h |  3 +++
 5 files changed, 46 insertions(+), 3 deletions(-)

diff --git a/xen/arch/x86/acpi/power.c b/xen/arch/x86/acpi/power.c
index 44de9c71d0..0763846548 100644
--- a/xen/arch/x86/acpi/power.c
+++ b/xen/arch/x86/acpi/power.c
@@ -254,6 +254,9 @@ static int enter_state(u32 state)
 
     microcode_resume_cpu(0);
 
+    if ( !recheck_cpu_features(0) )
+        panic("Missing previously available feature(s).");
+
     ci->bti_ist_info = default_bti_ist_info;
     asm volatile (ALTERNATIVE("", "wrmsr", X86_FEATURE_XEN_IBRS_SET)
                   :: "a" (SPEC_CTRL_IBRS), "c" (MSR_SPEC_CTRL), "d" (0)
diff --git a/xen/arch/x86/cpu/common.c b/xen/arch/x86/cpu/common.c
index 0a452aea2c..6a4e4a357f 100644
--- a/xen/arch/x86/cpu/common.c
+++ b/xen/arch/x86/cpu/common.c
@@ -501,6 +501,9 @@ void identify_cpu(struct cpuinfo_x86 *c)
        printk("\n");
 #endif
 
+       if (system_state == SYS_STATE_resume)
+               return;
+
        /*
         * On SMP, boot_cpu_data holds the common feature set between
         * all CPUs; so make sure that we indicate which features are
diff --git a/xen/arch/x86/cpuid.c b/xen/arch/x86/cpuid.c
index ac7f7af778..cff1a26043 100644
--- a/xen/arch/x86/cpuid.c
+++ b/xen/arch/x86/cpuid.c
@@ -473,6 +473,28 @@ void __init init_guest_cpuid(void)
     calculate_hvm_max_policy();
 }
 
+bool recheck_cpu_features(unsigned int cpu)
+{
+    bool okay = true;
+    struct cpuinfo_x86 c;
+    const struct cpuinfo_x86 *bsp = &boot_cpu_data;
+    unsigned int i;
+
+    identify_cpu(&c);
+
+    for ( i = 0; i < NCAPINTS; ++i )
+    {
+        if ( !(~c.x86_capability[i] & bsp->x86_capability[i]) )
+            continue;
+
+        printk(XENLOG_ERR "CPU%u: cap[%2u] is %08x (expected %08x)\n",
+               cpu, i, c.x86_capability[i], bsp->x86_capability[i]);
+        okay = false;
+    }
+
+    return okay;
+}
+
 const uint32_t *lookup_deep_deps(uint32_t feature)
 {
     static const struct {
diff --git a/xen/arch/x86/smpboot.c b/xen/arch/x86/smpboot.c
index 103d8f7142..0c38061896 100644
--- a/xen/arch/x86/smpboot.c
+++ b/xen/arch/x86/smpboot.c
@@ -90,11 +90,14 @@ void initialize_cpu_data(unsigned int cpu)
     cpu_data[cpu] = boot_cpu_data;
 }
 
-static void smp_store_cpu_info(int id)
+static bool smp_store_cpu_info(unsigned int id)
 {
     unsigned int socket;
 
-    identify_cpu(&cpu_data[id]);
+    if ( system_state != SYS_STATE_resume )
+        identify_cpu(&cpu_data[id]);
+    else if ( !recheck_cpu_features(id) )
+        return false;
 
     socket = cpu_to_socket(id);
     if ( !socket_cpumask[socket] )
@@ -102,6 +105,8 @@ static void smp_store_cpu_info(int id)
         socket_cpumask[socket] = secondary_socket_cpumask;
         secondary_socket_cpumask = NULL;
     }
+
+    return true;
 }
 
 /*
@@ -187,12 +192,19 @@ static void smp_callin(void)
     setup_local_APIC();
 
     /* Save our processor parameters. */
-    smp_store_cpu_info(cpu);
+    if ( !smp_store_cpu_info(cpu) )
+    {
+        printk("CPU%u: Failed to validate features - not coming back online\n",
+               cpu);
+        cpu_error = -ENXIO;
+        goto halt;
+    }
 
     if ( (rc = hvm_cpu_up()) != 0 )
     {
         printk("CPU%d: Failed to initialise HVM. Not coming online.\n", cpu);
         cpu_error = rc;
+    halt:
         clear_local_APIC();
         spin_debug_enable();
         cpu_exit_clear(cpu);
diff --git a/xen/include/asm-x86/cpuid.h b/xen/include/asm-x86/cpuid.h
index 74d6f123e5..4cce2686cb 100644
--- a/xen/include/asm-x86/cpuid.h
+++ b/xen/include/asm-x86/cpuid.h
@@ -253,6 +253,9 @@ static inline void cpuid_featureset_to_policy(
 extern struct cpuid_policy raw_cpuid_policy, host_cpuid_policy,
     pv_max_cpuid_policy, hvm_max_cpuid_policy;
 
+/* Check that all previously present features are still available. */
+bool recheck_cpu_features(unsigned int cpu);
+
 /* Allocate and initialise a CPUID policy suitable for the domain. */
 int init_domain_cpuid_policy(struct domain *d);
 
--
generated by git-patchbot for /home/xen/git/xen.git#master

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