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From: Bharata B Rao <bharata@linux.ibm.com>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxram@us.ibm.com, cclaudio@linux.ibm.com,
	kvm-ppc@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com,
	aneesh.kumar@linux.vnet.ibm.com, paulus@au1.ibm.com,
	sukadev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org,
	hch@lst.de
Subject: Re: [PATCH v10 6/8] KVM: PPC: Support reset of secure guest
Date: Mon, 11 Nov 2019 12:25:22 +0530
Message-ID: <20191111065522.GH21634@in.ibm.com> (raw)
In-Reply-To: <20191111052806.GC4017@oak.ozlabs.ibm.com>

On Mon, Nov 11, 2019 at 04:28:06PM +1100, Paul Mackerras wrote:
> On Mon, Nov 04, 2019 at 09:47:58AM +0530, Bharata B Rao wrote:
> > Add support for reset of secure guest via a new ioctl KVM_PPC_SVM_OFF.
> > This ioctl will be issued by QEMU during reset and includes the
> > the following steps:
> > 
> > - Ask UV to terminate the guest via UV_SVM_TERMINATE ucall
> > - Unpin the VPA pages so that they can be migrated back to secure
> >   side when guest becomes secure again. This is required because
> >   pinned pages can't be migrated.
> 
> Unpinning the VPA pages is normally handled during VM reset by QEMU
> doing set_one_reg operations to set the values for the
> KVM_REG_PPC_VPA_ADDR, KVM_REG_PPC_VPA_SLB and KVM_REG_PPC_VPA_DTL
> pseudo-registers to zero.  Is there some reason why this isn't
> happening for a secure VM, and if so, what is that reason?
> If it is happening, then why do we need to unpin the pages explicitly
> here?

We were observing these VPA pages still remaining pinned during
reset and hence subsequent paging-in of these pages were failing.
Unpinning them fixed the problem.

I will investigate and get back on why exactly these pages weren't
gettting unpinned normally as part of reset.

> 
> > - Reinitialize guest's partitioned scoped page tables. These are
> >   freed when guest becomes secure (H_SVM_INIT_DONE)
> 
> It doesn't seem particularly useful to me to free the partition-scoped
> page tables when the guest becomes secure, and it feels like it makes
> things more fragile.  If you don't free them then, then you don't need
> to reallocate them now.

Sure, I will not free them in the next version.

Regards,
Bharata.


  reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-04  4:17 [PATCH v10 0/8] KVM: PPC: Driver to manage pages " Bharata B Rao
2019-11-04  4:17 ` [PATCH v10 1/8] mm: ksm: Export ksm_madvise() Bharata B Rao
2019-11-06  4:33   ` Paul Mackerras
2019-11-06  6:45     ` Bharata B Rao
2019-11-07  5:45       ` Paul Mackerras
2019-11-15 14:10         ` Bharata B Rao
2019-11-04  4:17 ` [PATCH v10 2/8] KVM: PPC: Support for running secure guests Bharata B Rao
2019-11-06  4:34   ` Paul Mackerras
2019-11-04  4:17 ` [PATCH v10 3/8] KVM: PPC: Shared pages support for " Bharata B Rao
2019-11-06  4:52   ` Paul Mackerras
2019-11-06  8:22     ` Bharata B Rao
2019-11-06  8:29       ` Bharata B Rao
2019-11-04  4:17 ` [PATCH v10 4/8] KVM: PPC: Radix changes for secure guest Bharata B Rao
2019-11-06  5:58   ` Paul Mackerras
2019-11-06  8:36     ` Bharata B Rao
2019-11-04  4:17 ` [PATCH v10 5/8] KVM: PPC: Handle memory plug/unplug to secure VM Bharata B Rao
2019-11-11  4:25   ` Paul Mackerras
2019-11-04  4:17 ` [PATCH v10 6/8] KVM: PPC: Support reset of secure guest Bharata B Rao
2019-11-11  5:28   ` Paul Mackerras
2019-11-11  6:55     ` Bharata B Rao [this message]
2019-11-12  5:34   ` Paul Mackerras
2019-11-13 15:29     ` Bharata B Rao
2019-11-14  5:07       ` Paul Mackerras
2019-11-04  4:17 ` [PATCH v10 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall Bharata B Rao
2019-11-11  4:19   ` Paul Mackerras
2019-11-12  1:01     ` Ram Pai
2019-11-12  5:38       ` Paul Mackerras
2019-11-12  7:52         ` Ram Pai
2019-11-12 11:32           ` Paul Mackerras
2019-11-12 14:45             ` Ram Pai
2019-11-13  0:14               ` Paul Mackerras
2019-11-13  6:32                 ` Ram Pai
2019-11-13 21:18                   ` Paul Mackerras
2019-11-13 21:50                     ` Ram Pai
2019-11-14  5:08                       ` Paul Mackerras
2019-11-14  7:02                         ` Ram Pai
2019-11-04  4:18 ` [PATCH v10 8/8] KVM: PPC: Ultravisor: Add PPC_UV config option Bharata B Rao
2019-11-06  4:30 ` [PATCH v10 0/8] KVM: PPC: Driver to manage pages of secure guest Paul Mackerras
2019-11-06  6:20   ` Bharata B Rao

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