From mboxrd@z Thu Jan  1 00:00:00 1970
From: Suzuki.Poulose@arm.com (Suzuki K Poulose)
Date: Tue, 4 Apr 2017 11:14:01 +0100
Subject: [kvmarm:master 1/3] arch/arm/kvm/mmu.c:302:14: error:
 'S2_PUD_SIZE' undeclared
In-Reply-To: <201704040547.iQuSbIzK%fengguang.wu@intel.com>
References: <201704040547.iQuSbIzK%fengguang.wu@intel.com>
Message-ID: <cf4974ea-6cfd-331c-6a77-cf4c9f07812b@arm.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On 03/04/17 22:15, kbuild test robot wrote:
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/kvmarm/kvmarm.git master
> head:   1f1c45c6f66a586ca420ca02cbd93a35690394f9
> commit: f9d9eb7f7a2c7e388861fe1cdb253f63e63555fe [1/3] kvm: arm/arm64: Fix locking for kvm_free_stage2_pgd
> config: arm-axm55xx_defconfig (attached as .config)
> compiler: arm-linux-gnueabi-gcc (Debian 6.1.1-9) 6.1.1 20160705
> reproduce:
>         wget https://raw.githubusercontent.com/01org/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         git checkout f9d9eb7f7a2c7e388861fe1cdb253f63e63555fe
>         # save the attached .config to linux build tree
>         make.cross ARCH=arm
>
> All errors (new ones prefixed by >>):
>
>    arch/arm/kvm/mmu.c: In function 'unmap_stage2_range':
>>> arch/arm/kvm/mmu.c:302:14: error: 'S2_PUD_SIZE' undeclared (first use in this function)
>       if (size > S2_PUD_SIZE)
>                  ^~~~~~~~~~~

Thanks kbuild for catching this one !

>    arch/arm/kvm/mmu.c:302:14: note: each undeclared identifier is reported only once for each function it appears in
>
> vim +/S2_PUD_SIZE +302 arch/arm/kvm/mmu.c
>
>    296		pgd = kvm->arch.pgd + stage2_pgd_index(addr);
>    297		do {
>    298			/*
>    299			 * If the range is too large, release the kvm->mmu_lock
>    300			 * to prevent starvation and lockup detector warnings.
>    301			 */
>  > 302			if (size > S2_PUD_SIZE)
>    303				cond_resched_lock(&kvm->mmu_lock);
>    304			next = stage2_pgd_addr_end(addr, end);
>    305			if (!stage2_pgd_none(*pgd))
>


Marc, Christoffer,

Ah! I didn't test this on arm32. We have two options :

1) Define S2_P{U,M}_SIZE for arm32 in asm/stage2_pgtable.h

or,

2)  use the following hunk on top of the patch, which changes the lock
release after we process one PGDIR entry. As for the first time we enter
the loop we haven't done much with the lock held, hence it may make
sense to do it after the first round and we have more work to do.

Let me know what you think


diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
index db94f3a..582a972 100644
--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -295,15 +295,15 @@ static void unmap_stage2_range(struct kvm *kvm, phys_addr_t start, u64 size)
         assert_spin_locked(&kvm->mmu_lock);
         pgd = kvm->arch.pgd + stage2_pgd_index(addr);
         do {
+               next = stage2_pgd_addr_end(addr, end);
+               if (!stage2_pgd_none(*pgd))
+                       unmap_stage2_puds(kvm, pgd, addr, next);
                 /*
                  * If the range is too large, release the kvm->mmu_lock
                  * to prevent starvation and lockup detector warnings.
                  */
-               if (size > S2_PUD_SIZE)
+               if (next != end)
                         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);
         } while (pgd++, addr = next, addr != end);
  }
  

Suzuki

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