linux-kernel - [PATCH] KVM: arm/arm64: release kvm->mmu

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Date:   Wed, 15 Apr 2020 10:42:29 +0200
From:   Jiang Yi <giangyi@...zon.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     Jiang Yi <giangyi@...zon.com>, James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
        linux-kernel@...r.kernel.org
Subject: [PATCH] KVM: arm/arm64: release kvm->mmu_lock in loop to prevent starvation

Do cond_resched_lock() in stage2_flush_memslot() like what is done in
unmap_stage2_range() and other places holding mmu_lock while processing
a possibly large range of memory.

Signed-off-by: Jiang Yi <giangyi@...zon.com>
---
 virt/kvm/arm/mmu.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
index e3b9ee268823..7315af2c52f8 100644
--- a/virt/kvm/arm/mmu.c
+++ b/virt/kvm/arm/mmu.c
@@ -417,16 +417,19 @@ static void stage2_flush_memslot(struct kvm *kvm,
 	phys_addr_t next;
 	pgd_t *pgd;
 
 	pgd = kvm->arch.pgd + stage2_pgd_index(kvm, addr);
 	do {
 		next = stage2_pgd_addr_end(kvm, addr, end);
 		if (!stage2_pgd_none(kvm, *pgd))
 			stage2_flush_puds(kvm, pgd, addr, next);
+
+		if (next != end)
+			cond_resched_lock(&kvm->mmu_lock);
 	} while (pgd++, addr = next, addr != end);
 }
 
 /**
  * stage2_flush_vm - Invalidate cache for pages mapped in stage 2
  * @kvm: The struct kvm pointer
  *
  * Go through the stage 2 page tables and invalidate any cache lines
-- 
2.17.1