* Re: [PATCH] kvm:x86:Call BUG_ON marco if calls to x86_set_memory_region fail in kvm_arch_destroy
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@ 2015-08-07 8:54 ` Paolo Bonzini
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From: Paolo Bonzini @ 2015-08-07 8:54 UTC (permalink / raw)
To: Nicholas Krause, gleb; +Cc: x86, kvm, linux-kernel
On 06/08/2015 16:13, Nicholas Krause wrote:
> This fixes the calls to x86_memory_region to trigger a kernel
> oopes for tracing if a bug arises in the function kvm_arch_destroy
> due to the failing of any of its internal calls to x86_set_memory_region.
>
> Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
> ---
> arch/x86/kvm/x86.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 5ef2560..3866cf3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -7745,6 +7745,7 @@ EXPORT_SYMBOL_GPL(x86_set_memory_region);
>
> void kvm_arch_destroy_vm(struct kvm *kvm)
> {
> + int ret;
> if (current->mm == kvm->mm) {
> /*
> * Free memory regions allocated on behalf of userspace,
> @@ -7754,13 +7755,16 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
> struct kvm_userspace_memory_region mem;
> memset(&mem, 0, sizeof(mem));
> mem.slot = APIC_ACCESS_PAGE_PRIVATE_MEMSLOT;
> - x86_set_memory_region(kvm, &mem);
> + ret = x86_set_memory_region(kvm, &mem);
> + BUG_ON(ret);
>
> mem.slot = IDENTITY_PAGETABLE_PRIVATE_MEMSLOT;
> - x86_set_memory_region(kvm, &mem);
> + ret = x86_set_memory_region(kvm, &mem);
> + BUG_ON(ret);
>
> mem.slot = TSS_PRIVATE_MEMSLOT;
> - x86_set_memory_region(kvm, &mem);
> + ret = x86_set_memory_region(kvm, &mem);
> + BUG_ON(ret);
> }
> kvm_iommu_unmap_guest(kvm);
> kfree(kvm->arch.vpic);
>
No, not at all! Leaking 12k of RAM is not a reason to crash the
machine. WARN_ON would be acceptable.
Paolo
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