From: Paul Mackerras <paulus@ozlabs.org>
To: Alexey Kardashevskiy <aik@ozlabs.ru>
Cc: linuxppc-dev@lists.ozlabs.org,
David Gibson <david@gibson.dropbear.id.au>,
kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH kernel v2 6/6] KVM: PPC: Add support for multiple-TCE hcalls
Date: Fri, 12 Feb 2016 16:52:58 +1100 [thread overview]
Message-ID: <20160212055258.GA6219@fergus.ozlabs.ibm.com> (raw)
In-Reply-To: <56BD657A.1020203@ozlabs.ru>
On Fri, Feb 12, 2016 at 03:54:18PM +1100, Alexey Kardashevskiy wrote:
> On 02/11/2016 04:32 PM, Paul Mackerras wrote:
> >On Thu, Jan 21, 2016 at 06:39:37PM +1100, Alexey Kardashevskiy wrote:
> >>+ rmap = (void *) vmalloc_to_phys(rmap);
> >>+
> >>+ lock_rmap(rmap);
> >
> >A comment here explaining why we lock the rmap and what that achieves
> >would be useful for future generations.
>
>
> /* This protects the guest page with the TCE list from going away while we
> are reading TCE list */
>
> ?
>
> By "going away" I mean H_ENTER/H_REMOVE executed on parallel CPUs, is this
> roughly correct? as I did grep for "lock_rmap()" and did not find a single
> comment next to it...
Actually, taking the rmap lock stops the guest real -> host real
mapping from changing. For the comment, I suggest this:
/*
* Synchronize with the MMU notifier callbacks in
* book3s_64_mmu_hv.c (kvm_unmap_hva_hv etc.).
* While we have the rmap lock, code running on other CPUs
* cannot finish unmapping the host real page that backs
* this guest real page, so we are OK to access the host
* real page.
*/
Paul.
prev parent reply other threads:[~2016-02-12 5:53 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-21 7:39 [PATCH kernel v2 0/6] KVM: PPC: Add in-kernel multitce handling Alexey Kardashevskiy
2016-01-21 7:39 ` [PATCH kernel v2 1/6] KVM: PPC: Rework H_PUT_TCE/H_GET_TCE handlers Alexey Kardashevskiy
2016-01-22 0:42 ` David Gibson
2016-01-22 1:59 ` Alexey Kardashevskiy
2016-01-24 23:43 ` David Gibson
2016-02-11 4:11 ` Paul Mackerras
2016-01-21 7:39 ` [PATCH kernel v2 2/6] KVM: PPC: Use RCU for arch.spapr_tce_tables Alexey Kardashevskiy
2016-01-24 23:46 ` David Gibson
2016-01-21 7:39 ` [PATCH kernel v2 3/6] KVM: PPC: Account TCE-containing pages in locked_vm Alexey Kardashevskiy
2016-01-24 23:57 ` David Gibson
2016-01-21 7:39 ` [PATCH kernel v2 4/6] KVM: PPC: Replace SPAPR_TCE_SHIFT with IOMMU_PAGE_SHIFT_4K Alexey Kardashevskiy
2016-01-21 7:39 ` [PATCH kernel v2 5/6] KVM: PPC: Move reusable bits of H_PUT_TCE handler to helpers Alexey Kardashevskiy
2016-01-25 0:12 ` David Gibson
2016-01-25 0:18 ` David Gibson
2016-02-11 4:39 ` Paul Mackerras
2016-01-21 7:39 ` [PATCH kernel v2 6/6] KVM: PPC: Add support for multiple-TCE hcalls Alexey Kardashevskiy
2016-01-21 7:56 ` kbuild test robot
2016-01-21 8:09 ` Alexey Kardashevskiy
2016-01-25 0:44 ` David Gibson
2016-01-25 1:24 ` Alexey Kardashevskiy
2016-01-25 5:21 ` David Gibson
2016-02-11 5:32 ` Paul Mackerras
2016-02-12 4:54 ` Alexey Kardashevskiy
2016-02-12 5:52 ` Paul Mackerras [this message]
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