From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Will Deacon <will@kernel.org>, kvmarm@lists.cs.columbia.edu
Cc: Marc Zyngier <maz@kernel.org>,
kernel-team@android.com, linux-arm-kernel@lists.infradead.org,
Catalin Marinas <catalin.marinas@arm.com>
Subject: Re: [PATCH v3 09/21] KVM: arm64: Convert unmap_stage2_range() to generic page-table API
Date: Wed, 2 Sep 2020 19:44:51 +0100 [thread overview]
Message-ID: <10c6ca9b-c0f8-ae12-223c-42f1172b588a@arm.com> (raw)
In-Reply-To: <1f2e88b7-0265-195f-3bd8-4e1d5b8694e3@arm.com>
Hi Will,
I think I have answered my own question (again).
On 9/2/20 5:23 PM, Alexandru Elisei wrote:
> Hello,
>
> On 8/25/20 10:39 AM, Will Deacon wrote:
>> Convert unmap_stage2_range() to use kvm_pgtable_stage2_unmap() instead
>> of walking the page-table directly.
>>
>> Cc: Marc Zyngier <maz@kernel.org>
>> Cc: Quentin Perret <qperret@google.com>
>> Signed-off-by: Will Deacon <will@kernel.org>
>> ---
>> arch/arm64/kvm/mmu.c | 57 +++++++++++++++++++++++++-------------------
>> 1 file changed, 32 insertions(+), 25 deletions(-)
>>
>> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
>> index 704b471a48ce..751ce2462765 100644
>> --- a/arch/arm64/kvm/mmu.c
>> +++ b/arch/arm64/kvm/mmu.c
>> @@ -39,6 +39,33 @@ static bool is_iomap(unsigned long flags)
>> return flags & KVM_S2PTE_FLAG_IS_IOMAP;
>> }
>>
>> +/*
>> + * Release kvm_mmu_lock periodically if the memory region is large. Otherwise,
>> + * we may see kernel panics with CONFIG_DETECT_HUNG_TASK,
>> + * CONFIG_LOCKUP_DETECTOR, CONFIG_LOCKDEP. Additionally, holding the lock too
>> + * long will also starve other vCPUs. We have to also make sure that the page
>> + * tables are not freed while we released the lock.
>> + */
>> +#define stage2_apply_range(kvm, addr, end, fn, resched) \
>> +({ \
>> + int ret; \
>> + struct kvm *__kvm = (kvm); \
>> + bool __resched = (resched); \
>> + u64 next, __addr = (addr), __end = (end); \
>> + do { \
>> + struct kvm_pgtable *pgt = __kvm->arch.mmu.pgt; \
>> + if (!pgt) \
>> + break; \
> I'm 100% sure there's a reason why we've dropped the READ_ONCE, but it still looks
> to me like the compiler might decide to optimize by reading pgt once at the start
> of the loop and stashing it in a register. Would you mind explaining what I am
> missing?
I think the reason is that kvm_pgtable_stage2_unmap() has access to pgt via the
back pointer to mmu, and the function is in a different compilation unit now, so
the compiler cannot infer anything about pgt staying the same between function
calls. Is that correct?
Thanks,
Alex
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next prev parent reply other threads:[~2020-09-02 18:45 UTC|newest]
Thread overview: 86+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-25 9:39 [PATCH v3 00/21] KVM: arm64: Rewrite page-table code and fault handling Will Deacon
2020-08-25 9:39 ` [PATCH v3 01/21] KVM: arm64: Remove kvm_mmu_free_memory_caches() Will Deacon
2020-08-25 9:39 ` [PATCH v3 02/21] KVM: arm64: Add stand-alone page-table walker infrastructure Will Deacon
2020-08-27 16:27 ` Alexandru Elisei
2020-08-28 15:43 ` Alexandru Elisei
2020-09-02 10:36 ` Will Deacon
2020-08-28 15:51 ` Alexandru Elisei
2020-09-02 10:49 ` Will Deacon
2020-09-02 6:31 ` Gavin Shan
2020-09-02 11:02 ` Will Deacon
2020-09-03 1:11 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 03/21] KVM: arm64: Add support for creating kernel-agnostic stage-1 page tables Will Deacon
2020-08-28 15:35 ` Alexandru Elisei
2020-09-02 10:06 ` Will Deacon
2020-08-25 9:39 ` [PATCH v3 04/21] KVM: arm64: Use generic allocator for hyp stage-1 page-tables Will Deacon
2020-08-28 16:32 ` Alexandru Elisei
2020-09-02 11:35 ` Will Deacon
2020-09-02 14:48 ` Alexandru Elisei
2020-08-25 9:39 ` [PATCH v3 05/21] KVM: arm64: Add support for creating kernel-agnostic stage-2 page tables Will Deacon
2020-09-02 6:40 ` Gavin Shan
2020-09-02 11:30 ` Will Deacon
2020-08-25 9:39 ` [PATCH v3 06/21] KVM: arm64: Add support for stage-2 map()/unmap() in generic page-table Will Deacon
2020-09-01 16:24 ` Alexandru Elisei
2020-09-02 11:46 ` Will Deacon
2020-09-03 2:57 ` Gavin Shan
2020-09-03 5:27 ` Gavin Shan
2020-09-03 11:18 ` Gavin Shan
2020-09-03 12:30 ` Will Deacon
2020-09-03 16:15 ` Will Deacon
2020-09-04 0:47 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 07/21] KVM: arm64: Convert kvm_phys_addr_ioremap() to generic page-table API Will Deacon
2020-09-01 17:08 ` Alexandru Elisei
2020-09-02 11:48 ` Will Deacon
2020-09-03 3:57 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 08/21] KVM: arm64: Convert kvm_set_spte_hva() " Will Deacon
2020-09-02 15:37 ` Alexandru Elisei
2020-09-03 16:37 ` Will Deacon
2020-09-03 4:13 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 09/21] KVM: arm64: Convert unmap_stage2_range() " Will Deacon
2020-09-02 16:23 ` Alexandru Elisei
2020-09-02 18:44 ` Alexandru Elisei [this message]
2020-09-03 17:57 ` Will Deacon
2020-09-08 13:07 ` Alexandru Elisei
2020-09-09 10:57 ` Alexandru Elisei
2020-09-03 4:19 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 10/21] KVM: arm64: Add support for stage-2 page-aging in generic page-table Will Deacon
2020-09-03 4:33 ` Gavin Shan
2020-09-03 16:48 ` Will Deacon
2020-09-04 1:01 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 11/21] KVM: arm64: Convert page-aging and access faults to generic page-table API Will Deacon
2020-09-03 4:37 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 12/21] KVM: arm64: Add support for stage-2 write-protect in generic page-table Will Deacon
2020-09-03 4:47 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 13/21] KVM: arm64: Convert write-protect operation to generic page-table API Will Deacon
2020-09-03 4:48 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 14/21] KVM: arm64: Add support for stage-2 cache flushing in generic page-table Will Deacon
2020-09-03 4:51 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 15/21] KVM: arm64: Convert memslot cache-flushing code to generic page-table API Will Deacon
2020-09-03 4:52 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 16/21] KVM: arm64: Add support for relaxing stage-2 perms in generic page-table code Will Deacon
2020-09-03 4:55 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 17/21] KVM: arm64: Convert user_mem_abort() to generic page-table API Will Deacon
2020-09-03 6:05 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 18/21] KVM: arm64: Check the pgt instead of the pgd when modifying page-table Will Deacon
2020-09-03 5:00 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 19/21] KVM: arm64: Remove unused page-table code Will Deacon
2020-09-03 6:02 ` Gavin Shan
2020-08-25 9:39 ` [PATCH v3 20/21] KVM: arm64: Remove unused 'pgd' field from 'struct kvm_s2_mmu' Will Deacon
2020-09-03 5:07 ` Gavin Shan
2020-09-03 16:50 ` Will Deacon
2020-09-04 0:59 ` Gavin Shan
2020-09-04 10:02 ` Marc Zyngier
2020-08-25 9:39 ` [PATCH v3 21/21] KVM: arm64: Don't constrain maximum IPA size based on host configuration Will Deacon
2020-09-03 5:09 ` Gavin Shan
2020-08-27 16:26 ` [PATCH v3 00/21] KVM: arm64: Rewrite page-table code and fault handling Alexandru Elisei
2020-09-01 16:15 ` Will Deacon
2020-09-03 7:34 ` Gavin Shan
2020-09-03 11:13 ` Gavin Shan
2020-09-03 11:48 ` Gavin Shan
2020-09-03 12:16 ` Will Deacon
2020-09-04 0:51 ` Gavin Shan
2020-09-04 10:07 ` Marc Zyngier
2020-09-05 3:56 ` Gavin Shan
2020-09-05 9:33 ` Marc Zyngier
2020-09-07 9:27 ` Will Deacon
2020-09-03 18:52 ` Will Deacon
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