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From: Christian Borntraeger <borntraeger@de.ibm.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>, kvm@vger.kernel.org
Cc: 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
Subject: Re: [PATCH v4 06/14] KVM: s390: pv: properly handle page flags for protected guests
Date: Mon, 6 Sep 2021 17:46:40 +0200	[thread overview]
Message-ID: <1a44ff5c-f59f-2f37-2585-084294ed5e11@de.ibm.com> (raw)
In-Reply-To: <20210818132620.46770-7-imbrenda@linux.ibm.com>



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.
> ---
>   arch/s390/include/asm/pgtable.h |  9 ++++++---
>   arch/s390/include/asm/uv.h      | 10 ++++++++--
>   arch/s390/kernel/uv.c           | 34 ++++++++++++++++++++++++++++++++-
>   arch/s390/mm/gmap.c             |  4 +++-
>   4 files changed, 50 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/s390/include/asm/pgtable.h b/arch/s390/include/asm/pgtable.h
> index dcac7b2df72c..0f1af2232ebe 100644
> --- a/arch/s390/include/asm/pgtable.h
> +++ b/arch/s390/include/asm/pgtable.h
> @@ -1074,8 +1074,9 @@ static inline pte_t ptep_get_and_clear(struct mm_struct *mm,
>   	pte_t res;
>   
>   	res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
> +	/* At this point the reference through the mapping is still present */
>   	if (mm_is_protected(mm) && pte_present(res))
> -		uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> +		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
>   	return res;
>   }
>   
> @@ -1091,8 +1092,9 @@ static inline pte_t ptep_clear_flush(struct vm_area_struct *vma,
>   	pte_t res;
>   
>   	res = ptep_xchg_direct(vma->vm_mm, addr, ptep, __pte(_PAGE_INVALID));
> +	/* At this point the reference through the mapping is still present */
>   	if (mm_is_protected(vma->vm_mm) && pte_present(res))
> -		uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> +		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
>   	return res;
>   }
>   
> @@ -1116,8 +1118,9 @@ static inline pte_t ptep_get_and_clear_full(struct mm_struct *mm,
>   	} else {
>   		res = ptep_xchg_lazy(mm, addr, ptep, __pte(_PAGE_INVALID));
>   	}
> +	/* At this point the reference through the mapping is still present */
>   	if (mm_is_protected(mm) && pte_present(res))
> -		uv_convert_from_secure(pte_val(res) & PAGE_MASK);
> +		uv_convert_owned_from_secure(pte_val(res) & PAGE_MASK);
>   	return res;
>   }
>   
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index b35add51b967..3236293d5a31 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -356,8 +356,9 @@ static inline int is_prot_virt_host(void)
>   }
>   
>   int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb);
> -int uv_destroy_page(unsigned long paddr);
> +int uv_destroy_owned_page(unsigned long paddr);
>   int uv_convert_from_secure(unsigned long paddr);
> +int uv_convert_owned_from_secure(unsigned long paddr);
>   int gmap_convert_to_secure(struct gmap *gmap, unsigned long gaddr);
>   
>   void setup_uv(void);
> @@ -367,7 +368,7 @@ void adjust_to_uv_max(unsigned long *vmax);
>   static inline void setup_uv(void) {}
>   static inline void adjust_to_uv_max(unsigned long *vmax) {}
>   
> -static inline int uv_destroy_page(unsigned long paddr)
> +static inline int uv_destroy_owned_page(unsigned long paddr)
>   {
>   	return 0;
>   }
> @@ -376,6 +377,11 @@ static inline int uv_convert_from_secure(unsigned long paddr)
>   {
>   	return 0;
>   }
> +
> +static inline int uv_convert_owned_from_secure(unsigned long paddr)
> +{
> +	return 0;
> +}
>   #endif
>   
>   #if defined(CONFIG_PROTECTED_VIRTUALIZATION_GUEST) || IS_ENABLED(CONFIG_KVM)
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index 68a8fbafcb9c..05f8bf61d20a 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -115,7 +115,7 @@ static int uv_pin_shared(unsigned long paddr)
>    *
>    * @paddr: Absolute host address of page to be destroyed
>    */
> -int uv_destroy_page(unsigned long paddr)
> +static int uv_destroy_page(unsigned long paddr)
>   {
>   	struct uv_cb_cfs uvcb = {
>   		.header.cmd = UVC_CMD_DESTR_SEC_STOR,
> @@ -135,6 +135,22 @@ int uv_destroy_page(unsigned long paddr)
>   	return 0;
>   }
>   
> +/*
> + * 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);
> +	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);
> +	int rc;
> +
> +	get_page(page);
> +	rc = uv_convert_from_secure(paddr);
> +	if (!rc)
> +		clear_bit(PG_arch_1, &page->flags);
> +	put_page(page);
> +	return rc;
> +}
> +
>   /*
>    * Calculate the expected ref_count for a page that would otherwise have no
>    * further pins. This was cribbed from similar functions in other places in
> diff --git a/arch/s390/mm/gmap.c b/arch/s390/mm/gmap.c
> index 5a138f6220c4..38b792ab57f7 100644
> --- a/arch/s390/mm/gmap.c
> +++ b/arch/s390/mm/gmap.c
> @@ -2678,8 +2678,10 @@ static int __s390_reset_acc(pte_t *ptep, unsigned long addr,
>   {
>   	pte_t pte = READ_ONCE(*ptep);
>   
> +	/* There is a reference through the mapping */
>   	if (pte_present(pte))
> -		WARN_ON_ONCE(uv_destroy_page(pte_val(pte) & PAGE_MASK));
> +		WARN_ON_ONCE(uv_destroy_owned_page(pte_val(pte) & PAGE_MASK));
> +
>   	return 0;
>   }
>   
> 

  reply	other threads:[~2021-09-06 15:46 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 [this message]
2021-09-06 15:56     ` Claudio Imbrenda
2021-09-06 16:16       ` Christian Borntraeger
2021-09-17 14:57         ` Claudio Imbrenda
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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