From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Julien Grall <julien.grall@arm.com>,
Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xen.org
Subject: Re: [PATCH v3 7/8] xen/arm: Rework the interface of p2m_lookup and use typesafe gfn and mfn
Date: Fri, 24 Jun 2016 15:03:31 +0100 [thread overview]
Message-ID: <11bd382d-9a7b-868f-d809-dd18da57f118@citrix.com> (raw)
In-Reply-To: <576D3C6E.70800@arm.com>
On 24/06/16 14:58, Julien Grall wrote:
> Hi Stefano,
>
> On 23/06/16 15:14, Stefano Stabellini wrote:
>> On Tue, 21 Jun 2016, Julien Grall wrote:
>>> The prototype and the declaration of p2m_lookup disagree on how the
>>> function should be used. One expect a frame number whilst the other
>>> an address.
>>>
>>> Thankfully, everyone is using with an address today. However, most of
>>> the callers have to convert a guest frame to an address. Modify
>>> the interface to take a guest physical frame in parameter and return
>>> a machine frame.
>>>
>>> Whilst modifying the interface, use typesafe gfn and mfn for clarity
>>> and catching possible misusage.
>>>
>>> Signed-off-by: Julien Grall <julien.grall@arm.com>
>>> ---
>>> xen/arch/arm/p2m.c | 37 ++++++++++++++++++++-----------------
>>> xen/arch/arm/traps.c | 21 +++++++++++----------
>>> xen/include/asm-arm/p2m.h | 7 +++----
>>> 3 files changed, 34 insertions(+), 31 deletions(-)
>>>
>>> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
>>> index 47cb383..f3330dd 100644
>>> --- a/xen/arch/arm/p2m.c
>>> +++ b/xen/arch/arm/p2m.c
>>> @@ -140,14 +140,15 @@ void flush_tlb_domain(struct domain *d)
>>> }
>>>
>>> /*
>>> - * Lookup the MFN corresponding to a domain's PFN.
>>> + * Lookup the MFN corresponding to a domain's GFN.
>>> *
>>> * There are no processor functions to do a stage 2 only lookup
>>> therefore we
>>> * do a a software walk.
>>> */
>>> -static paddr_t __p2m_lookup(struct domain *d, paddr_t paddr,
>>> p2m_type_t *t)
>>> +static mfn_t __p2m_lookup(struct domain *d, gfn_t gfn, p2m_type_t *t)
>>> {
>>> struct p2m_domain *p2m = &d->arch.p2m;
>>> + const paddr_t paddr = pfn_to_paddr(gfn_x(gfn));
>>> const unsigned int offsets[4] = {
>>> zeroeth_table_offset(paddr),
>>> first_table_offset(paddr),
>>> @@ -158,7 +159,7 @@ static paddr_t __p2m_lookup(struct domain *d,
>>> paddr_t paddr, p2m_type_t *t)
>>> ZEROETH_MASK, FIRST_MASK, SECOND_MASK, THIRD_MASK
>>> };
>>> lpae_t pte, *map;
>>> - paddr_t maddr = INVALID_PADDR;
>>> + mfn_t mfn = _mfn(INVALID_MFN);
>>
>> It might be worth defining INVALID_MFN_T and just assign that to mfn.
>
> Good idea. It will be useful in other places too.
>
>>
>>> paddr_t mask = 0;
>>> p2m_type_t _t;
>>> unsigned int level, root_table;
>
>
> [...]
>
>>> @@ -1561,11 +1565,10 @@ p2m_mem_access_check_and_get_page(vaddr_t
>>> gva, unsigned long flag)
>>> * We had a mem_access permission limiting the access, but the
>>> page type
>>> * could also be limiting, so we need to check that as well.
>>> */
>>> - maddr = __p2m_lookup(current->domain, ipa, &t);
>>> - if ( maddr == INVALID_PADDR )
>>> + mfn = mfn_x(__p2m_lookup(current->domain, gfn, &t));
>>> + if ( mfn == INVALID_MFN )
>>
>> The conversion would go away if we had an INVALID_MFN which is mfn_t
Be careful.
INVALID_MFN_T is fine for assignment, but you can't do plain equality
tests of opaque structures.
mfn_t m = _mfn(0);
mfn_t inval = INVALID_MFN_T; // Ok
mfn_equal(m, INVALID_MFN_T); // Ok
mfn_equal(m, inval); // Ok
m == inval; // Compilation error
This was the reason that I didn't previously introduce INVALID_MFN_T,
although with mfn_equal(), perhaps the time has come.
~Andrew
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next prev parent reply other threads:[~2016-06-24 14:03 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-21 13:20 [PATCH v3 0/8] xen/arm: Use the typesafes gfn and mfn Julien Grall
2016-06-21 13:20 ` [PATCH v3 1/8] xen/arm: Rename gmfn_to_mfn to gfn_to_mfn and use gfn/mfn typesafe Julien Grall
2016-06-23 10:06 ` Stefano Stabellini
2016-06-21 13:20 ` [PATCH v3 2/8] xen/mm: Introduce a bunch of helpers for the typesafes mfn and gfn Julien Grall
2016-06-22 7:03 ` Jan Beulich
2016-06-21 13:20 ` [PATCH v3 3/8] xen: Use typesafe gfn/mfn in guest_physmap_* helpers Julien Grall
2016-06-23 10:11 ` Stefano Stabellini
2016-06-21 13:20 ` [PATCH v3 4/8] xen: Use typesafe gfn in xenmem_add_to_physmap_one Julien Grall
2016-06-23 10:20 ` Stefano Stabellini
2016-06-23 10:43 ` Julien Grall
2016-06-23 13:06 ` Stefano Stabellini
2016-06-23 13:33 ` Julien Grall
2016-06-23 13:41 ` Stefano Stabellini
2016-06-23 13:58 ` Stefano Stabellini
2016-06-21 13:20 ` [PATCH v3 5/8] xen/arm: Rename grant_table_gfpn into grant_table_gfn and use the typesafe gfn Julien Grall
2016-06-23 14:00 ` Stefano Stabellini
2016-06-21 13:20 ` [PATCH v3 6/8] xen: Use the typesafe mfn and gfn in map_mmio_regions Julien Grall
2016-06-23 14:05 ` Stefano Stabellini
2016-06-23 14:08 ` Julien Grall
2016-06-23 14:15 ` Stefano Stabellini
2016-06-23 14:58 ` Julien Grall
2016-06-21 13:20 ` [PATCH v3 7/8] xen/arm: Rework the interface of p2m_lookup and use typesafe gfn and mfn Julien Grall
2016-06-23 14:14 ` Stefano Stabellini
2016-06-24 13:58 ` Julien Grall
2016-06-24 14:03 ` Andrew Cooper [this message]
2016-06-21 13:20 ` [PATCH v3 8/8] xen/arm: p2m_cache_flush: Use the correct terminology and typesafe gfn Julien Grall
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