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From: Bharata B Rao <bharata@linux.ibm.com>
To: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
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,
	linuxppc-dev@lists.ozlabs.org, hch@lst.de
Subject: Re: [PATCH v8 2/8] kvmppc: Movement of pages between normal and secure memory
Date: Wed, 18 Sep 2019 12:42:06 +0530
Message-ID: <20190918071206.GA11675@in.ibm.com> (raw)
In-Reply-To: <20190917233139.GB27932@us.ibm.com>

On Tue, Sep 17, 2019 at 04:31:39PM -0700, Sukadev Bhattiprolu wrote:
> 
> Minor: Can this allocation be outside the lock? I guess it would change
> the order of cleanup at the end of the function.

Cleanup has bitmap_clear which needs be under spinlock, so this order
of setup/alloc and cleanup will keep things simple is what I felt.

> 
> > +	spin_unlock(&kvmppc_uvmem_pfn_lock);
> > +
> > +	*rmap = uvmem_pfn | KVMPPC_RMAP_UVMEM_PFN;
> > +	pvt->rmap = rmap;
> > +	pvt->gpa = gpa;
> > +	pvt->lpid = lpid;
> > +	dpage->zone_device_data = pvt;
> > +
> > +	get_page(dpage);
> > +	return dpage;
> > +
> > +out_unlock:
> > +	unlock_page(dpage);
> > +out_clear:
> > +	bitmap_clear(kvmppc_uvmem_pfn_bitmap, uvmem_pfn - pfn_first, 1);
> 
> Reuse variable 'bit'  here?

Sure.

> 
> > +out:
> > +	spin_unlock(&kvmppc_uvmem_pfn_lock);
> > +	return NULL;
> > +}
> > +
> > +/*
> > + * Alloc a PFN from private device memory pool and copy page from normal
> > + * memory to secure memory using UV_PAGE_IN uvcall.
> > + */
> > +static int
> > +kvmppc_svm_page_in(struct vm_area_struct *vma, unsigned long start,
> > +		   unsigned long end, unsigned long *rmap,
> > +		   unsigned long gpa, unsigned int lpid,
> > +		   unsigned long page_shift)
> > +{
> > +	unsigned long src_pfn, dst_pfn = 0;
> > +	struct migrate_vma mig;
> > +	struct page *spage;
> > +	unsigned long pfn;
> > +	struct page *dpage;
> > +	int ret = 0;
> > +
> > +	memset(&mig, 0, sizeof(mig));
> > +	mig.vma = vma;
> > +	mig.start = start;
> > +	mig.end = end;
> > +	mig.src = &src_pfn;
> > +	mig.dst = &dst_pfn;
> > +
> > +	ret = migrate_vma_setup(&mig);
> > +	if (ret)
> > +		return ret;
> > +
> > +	spage = migrate_pfn_to_page(*mig.src);
> > +	pfn = *mig.src >> MIGRATE_PFN_SHIFT;
> > +	if (!spage || !(*mig.src & MIGRATE_PFN_MIGRATE)) {
> > +		ret = 0;
> 
> Do we want to return success here (and have caller return H_SUCCESS) if
> we can't find the source page?

spage is NULL for zero page. In this case we return success but there is
no UV_PAGE_IN involved.

Absence of MIGRATE_PFN_MIGRATE indicates that the requested page
can't be migrated. I haven't hit this case till now. Similar check
is also present in the nouveau driver. I am not sure if this is strictly
needed here.

Christoph, Jason - do you know if !(*mig.src & MIGRATE_PFN_MIGRATE)
check is required and if so in which cases will it be true?

> > + * Fault handler callback when HV touches any page that has been
> 
>  Nit: s/callback/callback. Called /

Yeah will rephrase.

Regards,
Bharata.


  reply index

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-10  8:29 [PATCH v8 0/8] kvmppc: Driver to manage pages of secure guest Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 1/8] KVM: PPC: Book3S HV: Define usage types for rmap array in guest memslot Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 2/8] kvmppc: Movement of pages between normal and secure memory Bharata B Rao
2019-09-10  9:36   ` Bharata B Rao
2019-09-17 23:31   ` Sukadev Bhattiprolu
2019-09-18  7:12     ` Bharata B Rao [this message]
2019-09-18 10:47       ` Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 3/8] kvmppc: Shared pages support for secure guests Bharata B Rao
2019-09-17 23:33   ` Sukadev Bhattiprolu
2019-09-10  8:29 ` [PATCH v8 4/8] kvmppc: H_SVM_INIT_START and H_SVM_INIT_DONE hcalls Bharata B Rao
2019-09-17 23:35   ` Sukadev Bhattiprolu
2019-09-18  7:16     ` Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 5/8] kvmppc: Handle memory plug/unplug to secure VM Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 6/8] kvmppc: Radix changes for secure guest Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 7/8] kvmppc: Support reset of " Bharata B Rao
2019-09-17 23:27   ` Sukadev Bhattiprolu
2019-09-18  7:21     ` Bharata B Rao
2019-09-10  8:29 ` [PATCH v8 8/8] KVM: PPC: Ultravisor: Add PPC_UV config option Bharata B Rao
2019-09-17 23:37   ` Sukadev Bhattiprolu
2019-09-18  7:23     ` Bharata B Rao

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