On 15/08/18 14:04, Julien Grall wrote:
> Hi Andrew,
>
> On 08/13/2018 11:01 AM, Andrew Cooper wrote:
>> ... rather than setting the limits up after domain_create() has
>> completed.
>>
>> This removes all the gnttab infrastructure for calculating the number
>> of dom0
>> grant frames, opting instead to require the dom0 construction code to
>> pass a
>> sane value in via the configuration.
>>
>> In practice, this now means that there is never a partially
>> constructed grant
>> table for a reference-able domain.
>>
>> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
>> ---
>> CC: Jan Beulich <jbeul...@suse.com>
>> CC: Stefano Stabellini <sstabell...@kernel.org>
>> CC: Julien Grall <julien.gr...@arm.com>
>> CC: Wei Liu <wei.l...@citrix.com>
>>
>> v2:
>> * Split/rearrange to avoid the post-domain-create error path.
>> ---
>> xen/arch/arm/domain_build.c | 3 ++-
>> xen/arch/arm/setup.c | 12 ++++++++++++
>> xen/arch/x86/setup.c | 3 +++
>> xen/common/domain.c | 3 ++-
>> xen/common/grant_table.c | 16 +++-------------
>> xen/include/asm-arm/grant_table.h | 12 ------------
>> xen/include/asm-x86/grant_table.h | 5 -----
>> xen/include/xen/grant_table.h | 6 ++----
>> 8 files changed, 24 insertions(+), 36 deletions(-)
>>
>> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
>> index 1351572..737e0f3 100644
>> --- a/xen/arch/arm/domain_build.c
>> +++ b/xen/arch/arm/domain_build.c
>> @@ -2079,7 +2079,8 @@ static void __init find_gnttab_region(struct
>> domain *d,
>> * enough space for a large grant table
>> */
>> kinfo->gnttab_start = __pa(_stext);
>> - kinfo->gnttab_size = gnttab_dom0_frames() << PAGE_SHIFT;
>> + kinfo->gnttab_size = min_t(unsigned int, opt_max_grant_frames,
>> + PFN_DOWN(_etext - _stext)) <<
>> PAGE_SHIFT;
>
>
> I agree with Jan's comment on v1 that there is a risk someone will
> update the size here but ...
>
>
>> #ifdef CONFIG_ARM_32
>> /*
>> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
>> index 45f3841..3d3b30c 100644
>> --- a/xen/arch/arm/setup.c
>> +++ b/xen/arch/arm/setup.c
>> @@ -20,6 +20,7 @@
>> #include <xen/compile.h>
>> #include <xen/device_tree.h>
>> #include <xen/domain_page.h>
>> +#include <xen/grant_table.h>
>> #include <xen/types.h>
>> #include <xen/string.h>
>> #include <xen/serial.h>
>> @@ -693,6 +694,17 @@ void __init start_xen(unsigned long
>> boot_phys_offset,
>> struct domain *dom0;
>> struct xen_domctl_createdomain dom0_cfg = {
>> .max_evtchn_port = -1,
>> +
>> + /*
>> + * The region used by Xen on the memory will never be mapped
>> in DOM0
>> + * memory layout. Therefore it can be used for the grant table.
>> + *
>> + * Only use the text section as it's always present and will
>> contain
>> + * enough space for a large grant table
>> + */
>> + .max_grant_frames = min_t(unsigned int, opt_max_grant_frames,
>> + PFN_DOWN(_etext - _stext)),
>
> ... not here. So I would prefer if we either keep an helper to find
> the size of pass that size around to domain_build. Do we store the
> size in the domain information?
I have to admit that I'm somewhat perplexed by ARM's
find_gnttab_region(), and I'm not sure why it exists.
The value is available from d->grant_table.max_grant_frames but ISTR
finding that the order of construction meant that it wasn't available
when needed (although this was all from code inspection, so I could very
easily be wrong).
~Andrew
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