Messages in this thread Patch in this message | | | Subject | Re: [PATCH] KVM: arm/arm64: add WARN_ON if size is not PAGE_SIZE aligned in unmap_stage2_range | From | Jia He <> | Date | Thu, 17 May 2018 20:46:50 +0800 |
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Hi Suzuki
On 5/17/2018 4:17 PM, Suzuki K Poulose Wrote: > > Hi Jia, > > On 17/05/18 07:11, Jia He wrote: >> I ever met a panic under memory pressure tests(start 20 guests and run >> memhog in the host). > > Please avoid using "I" in the commit description and preferably stick to > an objective description.
Thanks for the pointing
> >> >> The root cause might be what I fixed at [1]. But from arm kvm points of >> view, it would be better we caught the exception earlier and clearer. >> >> If the size is not PAGE_SIZE aligned, unmap_stage2_range might unmap the >> wrong(more or less) page range. Hence it caused the "BUG: Bad page >> state" > > I don't see why we should ever panic with a "positive" size value. Anyways, > the unmap requests must be in units of pages. So this check might be useful. > >
good question,
After further digging, maybe we need to harden the break condition as below? diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c index 7f6a944..dac9b2e 100644 --- a/virt/kvm/arm/mmu.c +++ b/virt/kvm/arm/mmu.c @@ -217,7 +217,7 @@ static void unmap_stage2_ptes(struct kvm *kvm, pmd_t *pmd,
put_page(virt_to_page(pte)); } - } while (pte++, addr += PAGE_SIZE, addr != end); + } while (pte++, addr += PAGE_SIZE, addr < end);
basically verified in my armv8a server
-- Cheers, Jia > Reviewed-by: Suzuki K Poulose <suzuki.poulose@arm.com> >> >> [1] https://lkml.org/lkml/2018/5/3/1042 >> >> Signed-off-by: jia.he@hxt-semitech.com >> --- >> virt/kvm/arm/mmu.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c >> index 7f6a944..8dac311 100644 >> --- a/virt/kvm/arm/mmu.c >> +++ b/virt/kvm/arm/mmu.c >> @@ -297,6 +297,8 @@ static void unmap_stage2_range(struct kvm *kvm, >> phys_addr_t start, u64 size) >> phys_addr_t next; >> assert_spin_locked(&kvm->mmu_lock); >> + WARN_ON(size & ~PAGE_MASK); >> + >> pgd = kvm->arch.pgd + stage2_pgd_index(addr); >> do { >> /* >> > >
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