[kvm-devel] [PATCH] use slots_lock to protect writes to the wall clock

[Glauber Costa]

As Marcelo pointed out, we need slots_lock to protect
against slots changing under our nose during wall clock
writing.

This patch address this issue.

Signed-off-by: Glauber Costa <[EMAIL PROTECTED]>
CC: Marcelo Tosatti <[EMAIL PROTECTED]>
---
 arch/x86/kvm/x86.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1ef56ad..9e4c6f2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -500,21 +500,21 @@ static void kvm_write_wall_clock(struct 
        if (!wall_clock)
                return;
 
-       mutex_lock(&kvm->lock);
-
        version++;
+       
+       down_read(&kvm->slots_lock);
        kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
 
        wc_ts = current_kernel_time();
        wc.wc_sec = wc_ts.tv_sec;
        wc.wc_nsec = wc_ts.tv_nsec;
        wc.wc_version = version;
+
        kvm_write_guest(kvm, wall_clock, &wc, sizeof(wc));
 
        version++;
        kvm_write_guest(kvm, wall_clock, &version, sizeof(version));
-
-       mutex_unlock(&kvm->lock);
+       up_read(&kvm->slots_lock);
 }
 
 static void kvm_write_guest_time(struct kvm_vcpu *v)
@@ -608,8 +608,10 @@ int kvm_set_msr_common(struct kvm_vcpu *
                vcpu->arch.hv_clock.tsc_shift = 22;
 
                down_read(&current->mm->mmap_sem);
+               down_read(&vcpu->kvm->slots_lock);
                vcpu->arch.time_page =
                                gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT);
+               up_read(&vcpu->kvm->slots_lock);
                up_read(&current->mm->mmap_sem);
 
                if (is_error_page(vcpu->arch.time_page)) {
-- 
1.4.2


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