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From: Paul Mackerras <paulus@ozlabs.org>
To: Bharata B Rao <bharata@linux.ibm.com>
Cc: Sukadev Bhattiprolu <sukadev@linux.ibm.com>,
	linuxram@us.ibm.com, cclaudio@linux.ibm.com,
	kvm-ppc@vger.kernel.org, linux-mm@kvack.org, jglisse@redhat.com,
	Ram Pai <linuxram@linux.ibm.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 7/8] KVM: PPC: Implement H_SVM_INIT_ABORT hcall
Date: Mon, 11 Nov 2019 15:19:24 +1100
Message-ID: <20191111041924.GA4017@oak.ozlabs.ibm.com> (raw)
In-Reply-To: <20191104041800.24527-8-bharata@linux.ibm.com>

On Mon, Nov 04, 2019 at 09:47:59AM +0530, Bharata B Rao wrote:
> From: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
> 
> Implement the H_SVM_INIT_ABORT hcall which the Ultravisor can use to
> abort an SVM after it has issued the H_SVM_INIT_START and before the
> H_SVM_INIT_DONE hcalls. This hcall could be used when Ultravisor
> encounters security violations or other errors when starting an SVM.
> 
> Note that this hcall is different from UV_SVM_TERMINATE ucall which
> is used by HV to terminate/cleanup an SVM.
> 
> In case of H_SVM_INIT_ABORT, we should page-out all the pages back to
> HV (i.e., we should not skip the page-out). Otherwise the VM's pages,
> possibly including its text/data would be stuck in secure memory.
> Since the SVM did not go secure, its MSR_S bit will be clear and the
> VM wont be able to access its pages even to do a clean exit.

It seems fragile to me to have one more transfer back into the
ultravisor after this call.  Why does the UV need to do this call and
then get control back again one more time?  Why can't the UV defer
doing this call until it can do it without expecting to see a return
from the hcall?  And if it does need to see a return from the hcall,
what would happen if a malicious hypervisor doesn't do the return?

Paul.

  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 of secure guest 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
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 [this message]
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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