From: Alexandru Elisei <alexandru.elisei@arm.com>
To: Marc Zyngier <maz@kernel.org>,
linux-arm-kernel@lists.infradead.org, kvm@vger.kernel.org,
kvmarm@lists.cs.columbia.edu, linux-mm@kvack.org
Cc: Sean Christopherson <seanjc@google.com>,
Matthew Wilcox <willy@infradead.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Will Deacon <will@kernel.org>,
Quentin Perret <qperret@google.com>,
James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
kernel-team@android.com
Subject: Re: [PATCH 2/5] KVM: arm64: Avoid mapping size adjustment on permission fault
Date: Fri, 23 Jul 2021 16:55:39 +0100 [thread overview]
Message-ID: <a8f42fdf-4cbc-ad10-c8cc-cbbf850f85e4@arm.com> (raw)
In-Reply-To: <20210717095541.1486210-3-maz@kernel.org>
Hi Marc,
On 7/17/21 10:55 AM, Marc Zyngier wrote:
> Since we only support PMD-sized mappings for THP, getting
> a permission fault on a level that results in a mapping
> being larger than PAGE_SIZE is a sure indication that we have
> already upgraded our mapping to a PMD.
>
> In this case, there is no need to try and parse userspace page
> tables, as the fault information already tells us everything.
>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> ---
> arch/arm64/kvm/mmu.c | 11 ++++++++---
> 1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index db6314b93e99..c036a480ca27 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -1088,9 +1088,14 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
> * If we are not forced to use page mapping, check if we are
> * backed by a THP and thus use block mapping if possible.
> */
> - if (vma_pagesize == PAGE_SIZE && !(force_pte || device))
> - vma_pagesize = transparent_hugepage_adjust(kvm, memslot, hva,
> - &pfn, &fault_ipa);
> + if (vma_pagesize == PAGE_SIZE && !force_pte) {
Looks like now it's possible to call transparent_hugepage_adjust() for devices (if
fault_status != FSC_PERM). Commit 2aa53d68cee6 ("KVM: arm64: Try stage2 block
mapping for host device MMIO") makes a good case for the !device check. Was the
check removed unintentionally?
> + if (fault_status == FSC_PERM && fault_granule > PAGE_SIZE)
> + vma_pagesize = fault_granule;
> + else
> + vma_pagesize = transparent_hugepage_adjust(kvm, memslot,
> + hva, &pfn,
> + &fault_ipa);
> + }
This change makes sense to me - we can only get stage 2 permission faults on a
leaf entry since stage 2 tables don't have the APTable/XNTable/PXNTable bits. The
biggest block mapping size that we support at stage 2 is PMD size (from
transparent_hugepage_adjust()), therefore if fault_granule is larger than
PAGE_SIZE, then it must be PMD_SIZE.
Thanks,
Alex
>
> if (fault_status != FSC_PERM && !device && kvm_has_mte(kvm)) {
> /* Check the VMM hasn't introduced a new VM_SHARED VMA */
next prev parent reply other threads:[~2021-07-23 15:54 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-17 9:55 [PATCH 0/5] KVM: Remove kvm_is_transparent_hugepage() and friends Marc Zyngier
2021-07-17 9:55 ` [PATCH 1/5] KVM: arm64: Walk userspace page tables to compute the THP mapping size Marc Zyngier
2021-07-19 6:31 ` Paolo Bonzini
2021-07-19 9:31 ` Marc Zyngier
2021-07-20 17:23 ` Alexandru Elisei
2021-07-20 20:33 ` Sean Christopherson
2021-07-21 14:58 ` Will Deacon
2021-07-21 15:56 ` Sean Christopherson
2021-07-21 16:37 ` Alexandru Elisei
2021-07-23 8:48 ` Marc Zyngier
2021-07-17 9:55 ` [PATCH 2/5] KVM: arm64: Avoid mapping size adjustment on permission fault Marc Zyngier
2021-07-23 15:55 ` Alexandru Elisei [this message]
2021-07-23 16:18 ` Marc Zyngier
2021-07-17 9:55 ` [PATCH 3/5] KVM: Remove kvm_is_transparent_hugepage() and PageTransCompoundMap() Marc Zyngier
2021-07-19 6:31 ` Paolo Bonzini
2021-07-17 9:55 ` [PATCH 4/5] KVM: arm64: Use get_page() instead of kvm_get_pfn() Marc Zyngier
2021-07-17 9:55 ` [PATCH 5/5] KVM: Get rid " Marc Zyngier
2021-07-19 6:31 ` Paolo Bonzini
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=a8f42fdf-4cbc-ad10-c8cc-cbbf850f85e4@arm.com \
--to=alexandru.elisei@arm.com \
--cc=james.morse@arm.com \
--cc=kernel-team@android.com \
--cc=kvm@vger.kernel.org \
--cc=kvmarm@lists.cs.columbia.edu \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-mm@kvack.org \
--cc=maz@kernel.org \
--cc=pbonzini@redhat.com \
--cc=qperret@google.com \
--cc=seanjc@google.com \
--cc=suzuki.poulose@arm.com \
--cc=will@kernel.org \
--cc=willy@infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).