Patchwork [11/35] kvm: x86: Prevent sign extension of DR7 in guest debugging mode

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Submitter Marcelo Tosatti
Date Jan. 6, 2011, 5:56 p.m.
Message ID <8c5468319bca02b1c4ab1a65a1ac3f5e800413b5.1294336601.git.mtosatti@redhat.com>
Download mbox | patch
Permalink /patch/77759/
State New
Headers show

Comments

Marcelo Tosatti - Jan. 6, 2011, 5:56 p.m.
From: Jan Kiszka <jan.kiszka@siemens.com>

This unbreaks guest debugging when the 4th hardware breakpoint used for
guest debugging is a watchpoint of 4 or 8 byte lenght. The 31st bit of
DR7 is set in that case and used to cause a sign extension to the high
word which was breaking the guest state (vm entry failure).

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
---
 target-i386/kvm.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

Patch

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 7e5982b..85edacc 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -1686,7 +1686,7 @@  void kvm_arch_update_guest_debug(CPUState *env, struct kvm_guest_debug *dbg)
             dbg->arch.debugreg[n] = hw_breakpoint[n].addr;
             dbg->arch.debugreg[7] |= (2 << (n * 2)) |
                 (type_code[hw_breakpoint[n].type] << (16 + n*4)) |
-                (len_code[hw_breakpoint[n].len] << (18 + n*4));
+                ((uint32_t)len_code[hw_breakpoint[n].len] << (18 + n*4));
         }
     }
     /* Legal xcr0 for loading */