From: Andrew Cooper <andrew.cooper3@citrix.com>
Date: Thu, 24 May 2018 17:41:53 +0000 (+0000)
Subject: x86: Improvements to ler debugging
X-Git-Tag: archive/raspbian/4.14.0+80-gd101b417b7-1+rpi1^2~63^2~3702
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=3c675b32720518e87d879f47939b0965d726bab6;p=xen.git

x86: Improvements to ler debugging

 * Command line documentation for what the option does.
 * Implement a canonicalise_addr() helper and replace the opencoded use in
   sign_extend_msr()
 * Canonicalise the ler pointers and print symbol information.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
---

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 8a832c0f8b..4f75f64a90 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1247,6 +1247,12 @@ if left disabled by the BIOS.
 ### ler (x86)
 > `= <boolean>`
 
+> Default: false
+
+This option is intended for debugging purposes only.  Enable MSR_DEBUGCTL.LBR
+in hypervisor context to be able to dump the Last Interrupt/Exception To/From
+record with other registers.
+
 ### loglvl
 > `= <level>[/<rate-limited level>]` where level is `none | error | warning | info | debug | all`
 
diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
index e319bf10ba..4b08439484 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -4182,12 +4182,7 @@ static void sign_extend_msr(u32 msr, int type)
     struct vmx_msr_entry *entry;
 
     if ( (entry = vmx_find_msr(msr, type)) != NULL )
-    {
-        if ( entry->data & VADDR_TOP_BIT )
-            entry->data |= CANONICAL_MASK;
-        else
-            entry->data &= ~CANONICAL_MASK;
-    }
+        entry->data = canonicalise_addr(entry->data);
 }
 
 static void bdw_erratum_bdf14_fixup(void)
diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
index b0401850ef..ed02b788d3 100644
--- a/xen/arch/x86/x86_64/traps.c
+++ b/xen/arch/x86/x86_64/traps.c
@@ -150,7 +150,12 @@ void show_registers(const struct cpu_user_regs *regs)
 
         rdmsrl(ler_msr, from);
         rdmsrl(ler_msr + 1, to);
-        printk("ler: %016lx -> %016lx\n", from, to);
+
+        /* Upper bits may store metadata.  Re-canonicalise for printing. */
+        printk("ler: from %016"PRIx64" [%ps]\n",
+               from, _p(canonicalise_addr(from)));
+        printk("       to %016"PRIx64" [%ps]\n",
+               to, _p(canonicalise_addr(to)));
     }
 }
 
diff --git a/xen/include/asm-x86/x86_64/page.h b/xen/include/asm-x86/x86_64/page.h
index 05a0334893..4fe0205553 100644
--- a/xen/include/asm-x86/x86_64/page.h
+++ b/xen/include/asm-x86/x86_64/page.h
@@ -34,6 +34,14 @@
 
 #ifndef __ASSEMBLY__
 
+static inline unsigned long canonicalise_addr(unsigned long addr)
+{
+    if ( addr & VADDR_TOP_BIT )
+        return addr | CANONICAL_MASK;
+    else
+        return addr & ~CANONICAL_MASK;
+}
+
 #include <asm/types.h>
 
 #include <xen/pdx.h>