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[217.61.220.45]) by smtp.gmail.com with ESMTPSA id g41sm21629632wrg.53.2017.04.04.03.13.12 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 04 Apr 2017 03:13:12 -0700 (PDT) Date: Tue, 4 Apr 2017 12:13:16 +0200 From: Christoffer Dall To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, andreyknvl@google.com, dvyukov@google.com, marc.zyngier@arm.com, christoffer.dall@linaro.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, kcc@google.com, syzkaller@googlegroups.com, will.deacon@arm.com, catalin.marinas@arm.com, pbonzini@redhat.com, mark.rutland@arm.com, ard.biesheuvel@linaro.org, stable@vger.kernel.org Subject: Re: [PATCH v3] kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd Message-ID: <20170404101316.GF11752@cbox> References: <1491228763-23450-1-git-send-email-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1491228763-23450-1-git-send-email-suzuki.poulose@arm.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Hi Suzuki, On Mon, Apr 03, 2017 at 03:12:43PM +0100, Suzuki K Poulose wrote: > In kvm_free_stage2_pgd() we don't hold the kvm->mmu_lock while calling > unmap_stage2_range() on the entire memory range for the guest. This could > cause problems with other callers (e.g, munmap on a memslot) trying to > unmap a range. And since we have to unmap the entire Guest memory range > holding a spinlock, make sure we yield the lock if necessary, after we > unmap each PUD range. > > Fixes: commit d5d8184d35c9 ("KVM: ARM: Memory virtualization setup") > Cc: stable@vger.kernel.org # v3.10+ > Cc: Paolo Bonzini > Cc: Marc Zyngier > Cc: Christoffer Dall > Cc: Mark Rutland > Signed-off-by: Suzuki K Poulose > [ Avoid vCPU starvation and lockup detector warnings ] > Signed-off-by: Marc Zyngier > Signed-off-by: Suzuki K Poulose > This unfortunately fails to build on 32-bit ARM, and I also think we intended to check against S2_PGDIR_SIZE, not S2_PUD_SIZE. How about adding this to your patch (which includes a rename of S2_PGD_SIZE which is horribly confusing as it indicates the size of the first level stage-2 table itself, where S2_PGDIR_SIZE indicates the size of address space mapped by a single entry in the same table): Thanks, -Christoffer > --- > Changes since V2: > - Restrict kvm->mmu_lock relaxation to bigger ranges in unmap_stage2_range(), > to avoid possible issues like [0] > > [0] http://lists.infradead.org/pipermail/linux-arm-kernel/2017-March/498210.html > > Changes since V1: > - Yield the kvm->mmu_lock if necessary in unmap_stage2_range to prevent > vCPU starvation and lockup detector warnings. > --- > arch/arm/kvm/mmu.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c > index 13b9c1f..db94f3a 100644 > --- a/arch/arm/kvm/mmu.c > +++ b/arch/arm/kvm/mmu.c > @@ -292,8 +292,15 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) > phys_addr_t addr = start, end = start + size; > phys_addr_t next; > > + assert_spin_locked(&kvm->mmu_lock); > pgd = kvm->arch.pgd + stage2_pgd_index(addr); > do { > + /* > + * If the range is too large, release the kvm->mmu_lock > + * to prevent starvation and lockup detector warnings. > + */ > + if (size > S2_PUD_SIZE) > + cond_resched_lock(&kvm->mmu_lock); > next = stage2_pgd_addr_end(addr, end); > if (!stage2_pgd_none(*pgd)) > unmap_stage2_puds(kvm, pgd, addr, next); > @@ -831,7 +838,10 @@ void kvm_free_stage2_pgd(struct kvm *kvm) > if (kvm->arch.pgd == NULL) > return; > > + spin_lock(&kvm->mmu_lock); > unmap_stage2_range(kvm, 0, KVM_PHYS_SIZE); > + spin_unlock(&kvm->mmu_lock); > + > /* Free the HW pgd, one page at a time */ > free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE); > kvm->arch.pgd = NULL; > -- > 2.7.4 > diff --git a/arch/arm/include/asm/stage2_pgtable.h b/arch/arm/include/asm/stage2_pgtable.h index 460d616..c997f2d 100644 --- a/arch/arm/include/asm/stage2_pgtable.h +++ b/arch/arm/include/asm/stage2_pgtable.h @@ -35,10 +35,13 @@ #define stage2_pud_huge(pud) pud_huge(pud) +#define S2_PGDIR_SIZE PGDIR_SIZE +#define S2_PGDIR_MASK PGDIR_MASK + /* Open coded p*d_addr_end that can deal with 64bit addresses */ static inline phys_addr_t stage2_pgd_addr_end(phys_addr_t addr, phys_addr_t end) { - phys_addr_t boundary = (addr + PGDIR_SIZE) & PGDIR_MASK; + phys_addr_t boundary = (addr + S2_PGDIR_SIZE) & S2_PGDIR_MASK; return (boundary - 1 < end - 1) ? boundary : end; } diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index db94f3a..6e79a4c 100644 --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -41,7 +41,7 @@ static unsigned long hyp_idmap_start; static unsigned long hyp_idmap_end; static phys_addr_t hyp_idmap_vector; -#define S2_PGD_SIZE (PTRS_PER_S2_PGD * sizeof(pgd_t)) +#define S2_PGD_TABLE_SIZE (PTRS_PER_S2_PGD * sizeof(pgd_t)) #define hyp_pgd_order get_order(PTRS_PER_PGD * sizeof(pgd_t)) #define KVM_S2PTE_FLAG_IS_IOMAP (1UL << 0) @@ -299,7 +299,7 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size) * If the range is too large, release the kvm->mmu_lock * to prevent starvation and lockup detector warnings. */ - if (size > S2_PUD_SIZE) + if (size > S2_PGDIR_SIZE) cond_resched_lock(&kvm->mmu_lock); next = stage2_pgd_addr_end(addr, end); if (!stage2_pgd_none(*pgd)) @@ -747,7 +747,7 @@ int kvm_alloc_stage2_pgd(struct kvm *kvm) } /* Allocate the HW PGD, making sure that each page gets its own refcount */ - pgd = alloc_pages_exact(S2_PGD_SIZE, GFP_KERNEL | __GFP_ZERO); + pgd = alloc_pages_exact(S2_PGD_TABLE_SIZE, GFP_KERNEL | __GFP_ZERO); if (!pgd) return -ENOMEM; @@ -843,7 +843,7 @@ void kvm_free_stage2_pgd(struct kvm *kvm) spin_unlock(&kvm->mmu_lock); /* Free the HW pgd, one page at a time */ - free_pages_exact(kvm->arch.pgd, S2_PGD_SIZE); + free_pages_exact(kvm->arch.pgd, S2_PGD_TABLE_SIZE); kvm->arch.pgd = NULL; }