From: Oleksandr <olekstysh@gmail.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Oleksandr Tyshchenko" <oleksandr_tyshchenko@epam.com>,
"Ian Jackson" <iwj@xenproject.org>, "Wei Liu" <wl@xen.org>,
"Anthony PERARD" <anthony.perard@citrix.com>,
"Andrew Cooper" <andrew.cooper3@citrix.com>,
"George Dunlap" <george.dunlap@citrix.com>,
"Julien Grall" <julien@xen.org>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Juergen Gross" <jgross@suse.com>,
"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
xen-devel@lists.xenproject.org
Subject: Re: [RFC PATCH] xen: Introduce arch specific field to XEN_SYSCTL_physinfo
Date: Sun, 29 Aug 2021 23:28:42 +0300 [thread overview]
Message-ID: <8c622f4f-1931-3e2c-4f6e-9b832e8e435e@gmail.com> (raw)
In-Reply-To: <908e2d59-41f0-3bad-6030-b2889d9c5cc2@suse.com>
On 16.08.21 10:33, Jan Beulich wrote:
Hi Jan
Sorry for the late response.
> On 14.08.2021 01:28, Oleksandr Tyshchenko wrote:
>> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>>
>> We need to pass info about maximum supported address space size
>> to the toolstack on Arm in order to properly calculate the base
>> and size of the safe range for the guest. Use p2m_ipa_bits variable
>> which purpose is to hold the bit size of IPAs in P2M tables.
> What is "the safe range"?
It is unallocated (unused) address space which could be safely used by
domain for foreign/grant mappings on Arm, I will update description.
>
>> --- a/xen/include/public/arch-arm.h
>> +++ b/xen/include/public/arch-arm.h
>> @@ -332,6 +332,11 @@ struct xen_arch_domainconfig {
>> */
>> uint32_t clock_frequency;
>> };
>> +
>> +struct arch_physinfo {
>> + /* Holds the bit size of IPAs in p2m tables. */
>> + uint32_t p2m_ipa_bits;
>> +};
>> #endif /* __XEN__ || __XEN_TOOLS__ */
>>
>> struct arch_vcpu_info {
>> --- a/xen/include/public/arch-x86/xen.h
>> +++ b/xen/include/public/arch-x86/xen.h
>> @@ -346,6 +346,8 @@ typedef struct xen_msr_entry {
>> } xen_msr_entry_t;
>> DEFINE_XEN_GUEST_HANDLE(xen_msr_entry_t);
>>
>> +struct arch_physinfo {
>> +};
>> #endif /* !__ASSEMBLY__ */
> While the term "p2m_ipa_bits" surely isn't arch-agnostic, I wonder
> whether the expressed information is (the x86 equivalent being
> hap_paddr_bits, at a guess), and hence whether this really ought
> to live in an arch-specific sub-struct.
Well, on Arm we calculate the number of the IPA bits based on the number
of PA bits when setting Stage 2 address translation.
I might mistake, but what we currently have on Arm is "ipa_bits ==
pa_bits". So, this means that information we need at the toolstack side
isn't really arch-specific and
we could probably avoid introducing arch-specific sub-struct by suitable
renaming the field (pa_bits, paddr_bits, whatever).
We could even name the field as hap_paddr_bits. Although, I don't know
whether the hap_* is purely x86-ism, but I see there are several
mentions in the common code (hap_pt_share, use_hap_pt, etc). Any
suggestions?
> If indeed so, please name
> the struct in a name space clean way, i.e. add xen_ as prefix.
ok
>
> Also please retain a blank line before the #endif. I wonder whether
> on Arm you wouldn't want to add one at this occasion.
ok
>
> Jan
>
--
Regards,
Oleksandr Tyshchenko
next prev parent reply other threads:[~2021-08-29 20:29 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-13 23:28 [RFC PATCH] xen: Introduce arch specific field to XEN_SYSCTL_physinfo Oleksandr Tyshchenko
2021-08-16 7:33 ` Jan Beulich
2021-08-29 20:28 ` Oleksandr [this message]
2021-08-30 13:16 ` Jan Beulich
2021-08-30 16:14 ` Oleksandr
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