From: mingyu84.kim@samsung•com (Min-gyu Kim)
To: linux-arm-kernel@lists•infradead.org
Subject: [kvmarm] [PATCH v2 06/14] KVM: ARM: Memory virtualization setup
Date: Wed, 10 Oct 2012 10:02:11 +0900 [thread overview]
Message-ID: <001501cda682$e220eba0$a662c2e0$@samsung.com> (raw)
In-Reply-To: <6994599196536c9557528c465f8f93b0@localhost>
> -----Original Message-----
> From: Marc Zyngier [mailto:marc.zyngier at arm.com]
> Sent: Tuesday, October 09, 2012 9:56 PM
> To: Christoffer Dall
> Cc: Min-gyu Kim; ???; linux-arm-kernel at lists.infradead.org;
> kvm at vger.kernel.org; kvmarm at lists.cs.columbia.edu
> Subject: Re: [kvmarm] [PATCH v2 06/14] KVM: ARM: Memory virtualization
> setup
>
> On Sat, 6 Oct 2012 17:33:43 -0400, Christoffer Dall
> <c.dall@virtualopensystems•com> wrote:
> > On Thu, Oct 4, 2012 at 10:23 PM, Min-gyu Kim
> > <mingyu84.kim@samsung•com>
> > wrote:
> >>
> >>
> >>> -----Original Message-----
> >>> From: kvm-owner at vger.kernel.org [mailto:kvm-owner at vger.kernel.org]
> >>> On Behalf Of Christoffer Dall
> >>> Sent: Monday, October 01, 2012 6:11 PM
> >>> To: kvm at vger.kernel.org; linux-arm-kernel at lists.infradead.org;
> >>> kvmarm at lists.cs.columbia.edu
> >>> Cc: Marc Zyngier
> >>> Subject: [PATCH v2 06/14] KVM: ARM: Memory virtualization setup
> >>>
> >>> +static void stage2_set_pte(struct kvm *kvm, struct
> kvm_mmu_memory_cache
> >>> *cache,
> >>> + phys_addr_t addr, const pte_t *new_pte) {
> >>> + pgd_t *pgd;
> >>> + pud_t *pud;
> >>> + pmd_t *pmd;
> >>> + pte_t *pte, old_pte;
> >>> +
> >>> + /* Create 2nd stage page table mapping - Level 1 */
> >>> + pgd = kvm->arch.pgd + pgd_index(addr);
> >>> + pud = pud_offset(pgd, addr);
> >>> + if (pud_none(*pud)) {
> >>> + if (!cache)
> >>> + return; /* ignore calls from kvm_set_spte_hva */
> >>> + pmd = mmu_memory_cache_alloc(cache);
> >>> + pud_populate(NULL, pud, pmd);
> >>> + pmd += pmd_index(addr);
> >>> + get_page(virt_to_page(pud));
> >>> + } else
> >>> + pmd = pmd_offset(pud, addr);
> >>> +
> >>> + /* Create 2nd stage page table mapping - Level 2 */
> >>> + if (pmd_none(*pmd)) {
> >>> + if (!cache)
> >>> + return; /* ignore calls from kvm_set_spte_hva */
> >>> + pte = mmu_memory_cache_alloc(cache);
> >>> + clean_pte_table(pte);
> >>> + pmd_populate_kernel(NULL, pmd, pte);
> >>> + pte += pte_index(addr);
> >>> + get_page(virt_to_page(pmd));
> >>> + } else
> >>> + pte = pte_offset_kernel(pmd, addr);
> >>> +
> >>> + /* Create 2nd stage page table mapping - Level 3 */
> >>> + old_pte = *pte;
> >>> + set_pte_ext(pte, *new_pte, 0);
> >>> + if (pte_present(old_pte))
> >>> + __kvm_tlb_flush_vmid(kvm);
> >>> + else
> >>> + get_page(virt_to_page(pte)); }
> >>
> >>
> >> I'm not sure about the 3-level page table, but isn't it necessary to
> >> clean the page table for 2nd level?
> >> There are two mmu_memory_cache_alloc calls. One has following
> >> clean_pte_table and the other doesn't have.
> >
> > hmm, it probably is - I couldn't really find the common case where
> > this is done in the kernel normally (except for some custom loop in
> > ioremap and idmap), but I added this fix:
> >
> > diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index
> > 5394a52..f11ba27f 100644
> > --- a/arch/arm/kvm/mmu.c
> > +++ b/arch/arm/kvm/mmu.c
> > @@ -430,6 +430,7 @@ static void stage2_set_pte(struct kvm *kvm, struct
> > kvm_mmu_memory_cache *cache,
> > if (!cache)
> > return; /* ignore calls from kvm_set_spte_hva */
> > pmd = mmu_memory_cache_alloc(cache);
> > + clean_dcache_area(pmd, PTRS_PER_PMD * sizeof(pmd_t));
> > pud_populate(NULL, pud, pmd);
> > pmd += pmd_index(addr);
> > get_page(virt_to_page(pud));
>
> There ought to be a test of ID_MMFR3[23:20] to find out whether or not it
> is useful to clean the dcache. Not sure if that's a massive gain, but it
> is certainly an optimisation to consider for the kernel as a whole.
That's part of what I was wondering. clean_dcache_area is substituted by nop if
TLB_CAN_READ_FROM_L1_CACHE is defined(mm/proc-v7.S).
But I couldn't find any place where it is defined.
If it is part of bsp to enable TLB_CAN_RAD_FROM_L1_CACHE according to ID_MMFR3[23:20],
it would not be necessary to concerned about cleaning or not cleaning.
However, am I right?
>
> M.
> --
> Fast, cheap, reliable. Pick two.
next prev parent reply other threads:[~2012-10-10 1:02 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-01 9:09 [PATCH v2 00/14] KVM/ARM Implementation Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 01/14] ARM: Add page table and page defines needed by KVM Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 02/14] ARM: Section based HYP idmap Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 03/14] ARM: Factor out cpuid implementor and part number Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 04/14] KVM: ARM: Initial skeleton to compile KVM support Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 05/14] KVM: ARM: Hypervisor inititalization Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 06/14] KVM: ARM: Memory virtualization setup Christoffer Dall
2012-10-05 2:23 ` Min-gyu Kim
2012-10-06 21:33 ` Christoffer Dall
2012-10-09 12:56 ` [kvmarm] " Marc Zyngier
2012-10-10 1:02 ` Min-gyu Kim [this message]
2012-10-01 9:10 ` [PATCH v2 07/14] KVM: ARM: Inject IRQs and FIQs from userspace Christoffer Dall
2012-10-01 9:10 ` [PATCH v2 08/14] KVM: ARM: World-switch implementation Christoffer Dall
2012-10-01 9:11 ` [PATCH v2 09/14] KVM: ARM: Emulation framework and CP15 emulation Christoffer Dall
2012-10-01 9:11 ` [PATCH v2 10/14] KVM: ARM: User space API for getting/setting co-proc registers Christoffer Dall
2012-10-01 9:11 ` [PATCH v2 11/14] KVM: ARM: Demux CCSIDR in the userspace API Christoffer Dall
2012-10-01 9:11 ` [PATCH v2 12/14] KVM: ARM: VFP userspace interface Christoffer Dall
2012-10-09 18:11 ` [kvmarm] " Peter Maydell
2012-10-09 18:13 ` Christoffer Dall
2012-10-11 1:42 ` Rusty Russell
2012-10-01 9:11 ` [PATCH v2 13/14] KVM: ARM: Handle guest faults in KVM Christoffer Dall
2012-10-01 9:11 ` [PATCH v2 14/14] KVM: ARM: Handle I/O aborts Christoffer Dall
2012-10-10 18:47 ` [PATCH v2 00/14] KVM/ARM Implementation Marcelo Tosatti
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='001501cda682$e220eba0$a662c2e0$@samsung.com' \
--to=mingyu84.kim@samsung$(echo .)com \
--cc=linux-arm-kernel@lists$(echo .)infradead.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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