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kvm: x86: Prevent sign extension of DR7 in guest debugging mode

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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>
This commit is contained in:
Jan Kiszka 2010-12-27 15:58:23 +01:00 committed by Marcelo Tosatti
parent 3980e3024b
commit 95c077c919
1 changed files with 1 additions and 1 deletions
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2
target-i386/kvm.c
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@ -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 */