Re: [PATCH v3 13/21] KVM: arm64: Convert write-protect operation to generic page-table API

Gavin Shan
2020-09-03T04:49:35Z

Hi Will,

On 8/25/20 7:39 PM, Will Deacon wrote:
> From: Quentin Perret <qperret@google.com>
>
> Convert stage2_wp_range() to call the kvm_pgtable_stage2_wrprotect()
> function of the generic page-table code instead of walking the page-table
> directly.
>
> Cc: Marc Zyngier <maz@kernel.org>
> Signed-off-by: Quentin Perret <qperret@google.com>
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
> arch/arm64/kvm/mmu.c | 25 ++++---------------------
> 1 file changed, 4 insertions(+), 21 deletions(-)
>

Reviewed-by: Gavin Shan <gshan@redhat.com>

> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index d3db8e00ce0a..ca2c37c91e0b 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -66,6 +66,9 @@ static bool is_iomap(unsigned long flags)
> ret; \
> })
>
> +#define stage2_apply_range_resched(kvm, addr, end, fn) \
> + stage2_apply_range(kvm, addr, end, fn, true)
> +
> static bool memslot_is_logging(struct kvm_memory_slot *memslot)
> {
> return memslot->dirty_bitmap && !(memslot->flags & KVM_MEM_READONLY);
> @@ -1294,27 +1297,7 @@ static void stage2_wp_p4ds(struct kvm_s2_mmu *mmu, pgd_t *pgd,
> static void stage2_wp_range(struct kvm_s2_mmu *mmu, phys_addr_t addr, phys_addr_t end)
> {
> struct kvm *kvm = mmu->kvm;
> - pgd_t *pgd;
> - phys_addr_t next;
> -
> - pgd = mmu->pgd + stage2_pgd_index(kvm, addr);
> - do {
> - /*
> - * 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.
> - */
> - cond_resched_lock(&kvm->mmu_lock);
> - if (!READ_ONCE(mmu->pgd))
> - break;
> - next = stage2_pgd_addr_end(kvm, addr, end);
> - if (stage2_pgd_present(kvm, *pgd))
> - stage2_wp_p4ds(mmu, pgd, addr, next);
> - } while (pgd++, addr = next, addr != end);
> + stage2_apply_range_resched(kvm, addr, end, kvm_pgtable_stage2_wrprotect);
> }
>
> /**
>

Thanks,
Gavin