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From: Claudio Imbrenda <imbrenda@linux.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: kvm@vger.kernel.org, cohuck@redhat.com, frankja@linux.ibm.com,
	thuth@redhat.com, pasic@linux.ibm.com, david@redhat.com,
	linux-s390@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ulrich.Weigand@de.ibm.com,
	Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Subject: Re: [PATCH v4 06/14] KVM: s390: pv: properly handle page flags for protected guests
Date: Fri, 17 Sep 2021 16:57:35 +0200	[thread overview]
Message-ID: <20210917165735.1e86d02b@p-imbrenda> (raw)
In-Reply-To: <35e4b7a3-42d8-6b8f-e2e7-5b6a81dfcfa3@de.ibm.com>

On Mon, 6 Sep 2021 18:16:10 +0200
Christian Borntraeger <borntraeger@de.ibm.com> wrote:

> On 06.09.21 17:56, Claudio Imbrenda wrote:
> > On Mon, 6 Sep 2021 17:46:40 +0200
> > Christian Borntraeger <borntraeger@de.ibm.com> wrote:
> >   
> >> On 18.08.21 15:26, Claudio Imbrenda wrote:  
> >>> Introduce variants of the convert and destroy page functions that also
> >>> clear the PG_arch_1 bit used to mark them as secure pages.
> >>>
> >>> These new functions can only be called on pages for which a reference
> >>> is already being held.
> >>>
> >>> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> >>> Acked-by: Janosch Frank <frankja@linux.ibm.com>  
> >>
> >> Can you refresh my mind? We do have over-indication of PG_arch_1 and this
> >> might result in spending some unneeded cycles but in the end this will be
> >> correct. Right?
> >> And this patch will fix some unnecessary places that add overindication.  
> > 
> > correct, PG_arch_1 will still overindicate, but with this patch it will
> > happen less.
> > 
> > And PG_arch_1 overindication is perfectly fine from a correctness point
> > of view.  
> 
> Maybe add something like this to the patch description then.
> 
> >>> +/*
> >>> + * The caller must already hold a reference to the page
> >>> + */
> >>> +int uv_destroy_owned_page(unsigned long paddr)
> >>> +{
> >>> +	struct page *page = phys_to_page(paddr);  
> 
> Do we have to protect against weird mappings without struct page here? I have not
> followed the discussion about this topic. Maybe Gerald knows if we can have memory
> without struct pages.

at first glance, it seems we can't have mappings without a struct page

> 
> >>> +	int rc;
> >>> +
> >>> +	get_page(page);
> >>> +	rc = uv_destroy_page(paddr);
> >>> +	if (!rc)
> >>> +		clear_bit(PG_arch_1, &page->flags);
> >>> +	put_page(page);
> >>> +	return rc;
> >>> +}
> >>> +
> >>>    /*
> >>>     * Requests the Ultravisor to encrypt a guest page and make it
> >>>     * accessible to the host for paging (export).
> >>> @@ -154,6 +170,22 @@ int uv_convert_from_secure(unsigned long paddr)
> >>>    	return 0;
> >>>    }
> >>>    
> >>> +/*
> >>> + * The caller must already hold a reference to the page
> >>> + */
> >>> +int uv_convert_owned_from_secure(unsigned long paddr)
> >>> +{
> >>> +	struct page *page = phys_to_page(paddr);  
> 
> Same here. If this is not an issue (and you add something to the patch description as
> outlined above)
> 
> Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
> 
> 


  reply	other threads:[~2021-09-17 14:57 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 13:26 [PATCH v4 00/14] KVM: s390: pv: implement lazy destroy for reboot Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 01/14] KVM: s390: pv: add macros for UVC CC values Claudio Imbrenda
2021-08-31 13:43   ` Christian Borntraeger
2021-08-18 13:26 ` [PATCH v4 02/14] KVM: s390: pv: avoid double free of sida page Claudio Imbrenda
2021-08-31 13:55   ` Christian Borntraeger
2021-09-08 18:50     ` Claudio Imbrenda
2021-08-31 13:59   ` Janosch Frank
2021-08-18 13:26 ` [PATCH v4 03/14] KVM: s390: pv: avoid stalls for kvm_s390_pv_init_vm Claudio Imbrenda
2021-08-31 14:10   ` Christian Borntraeger
2021-08-18 13:26 ` [PATCH v4 04/14] KVM: s390: pv: avoid stalls when making pages secure Claudio Imbrenda
2021-08-31 14:32   ` Christian Borntraeger
2021-08-31 15:00     ` Claudio Imbrenda
2021-08-31 15:11       ` Christian Borntraeger
2021-08-18 13:26 ` [PATCH v4 05/14] KVM: s390: pv: leak the ASCE page when destroy fails Claudio Imbrenda
2021-09-06 15:32   ` Christian Borntraeger
2021-09-06 15:54     ` Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 06/14] KVM: s390: pv: properly handle page flags for protected guests Claudio Imbrenda
2021-09-06 15:46   ` Christian Borntraeger
2021-09-06 15:56     ` Claudio Imbrenda
2021-09-06 16:16       ` Christian Borntraeger
2021-09-17 14:57         ` Claudio Imbrenda [this message]
2021-08-18 13:26 ` [PATCH v4 07/14] KVM: s390: pv: handle secure storage violations " Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 08/14] KVM: s390: pv: handle secure storage exceptions for normal guests Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 09/14] KVM: s390: pv: refactor s390_reset_acc Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 10/14] KVM: s390: pv: usage counter instead of flag Claudio Imbrenda
2021-08-26  7:58   ` Janis Schoetterl-Glausch
2021-08-18 13:26 ` [PATCH v4 11/14] KVM: s390: pv: add export before import Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 12/14] KVM: s390: pv: module parameter to fence lazy destroy Claudio Imbrenda
2021-08-18 13:26 ` [PATCH v4 13/14] KVM: s390: pv: lazy destroy for reboot Claudio Imbrenda
2021-08-26  8:33   ` Janis Schoetterl-Glausch
2021-08-18 13:26 ` [PATCH v4 14/14] KVM: s390: pv: avoid export before import if possible Claudio Imbrenda

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