[PATCH 2/6] x86: Improvements to ler debugging

From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Xen-devel <xen-devel@lists.xen.org>
Cc: "Kevin Tian" <kevin.tian@intel.com>,
	"Wei Liu" <wei.liu2@citrix.com>,
	"Jan Beulich" <JBeulich@suse.com>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Jun Nakajima" <jun.nakajima@intel.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: [PATCH 2/6] x86: Improvements to ler debugging
Date: Mon, 28 May 2018 15:27:54 +0100	[thread overview]
Message-ID: <1527517678-1779-3-git-send-email-andrew.cooper3@citrix.com> (raw)
In-Reply-To: <1527517678-1779-1-git-send-email-andrew.cooper3@citrix.com>

 * 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>
---
CC: Jan Beulich <JBeulich@suse.com>
CC: Jun Nakajima <jun.nakajima@intel.com>
CC: Kevin Tian <kevin.tian@intel.com>
CC: Wei Liu <wei.liu2@citrix.com>
CC: Roger Pau Monné <roger.pau@citrix.com>
---
 docs/misc/xen-command-line.markdown | 6 ++++++
 xen/arch/x86/hvm/vmx/vmx.c          | 7 +------
 xen/arch/x86/x86_64/traps.c         | 7 ++++++-
 xen/include/asm-x86/x86_64/page.h   | 8 ++++++++
 4 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-command-line.markdown
index 8712a83..1212ebd 100644
--- a/docs/misc/xen-command-line.markdown
+++ b/docs/misc/xen-command-line.markdown
@@ -1245,6 +1245,12 @@ if left disabled by the BIOS.
 ### ler (x86)
 > `= <boolean>`
 
+> Default: 0
+
+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 33d39f6..8049264 100644
--- a/xen/arch/x86/hvm/vmx/vmx.c
+++ b/xen/arch/x86/hvm/vmx/vmx.c
@@ -4183,12 +4183,7 @@ 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 b040185..ed02b78 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 05a0334..4fe0205 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>
-- 
2.1.4


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