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Re: [Xen-devel] [PATCH] x86/vcpu: Remove struct vcpu allocation restriction for !CONFIG_SHADOW_PAGING
- To: Jan Beulich <JBeulich@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: George Dunlap <george.dunlap@xxxxxxxxxx>
- Date: Mon, 5 Nov 2018 10:41:55 +0000
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- Cc: George Dunlap <George.Dunlap@xxxxxxxxxxxxx>, Tim Deegan <tim@xxxxxxx>, Wei Liu <wei.liu2@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxx>
- Delivery-date: Mon, 05 Nov 2018 10:42:11 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Openpgp: preference=signencrypt
On 11/05/2018 08:50 AM, Jan Beulich wrote:
>>>> On 02.11.18 at 18:54, <andrew.cooper3@xxxxxxxxxx> wrote:
>> --- a/xen/arch/x86/domain.c
>> +++ b/xen/arch/x86/domain.c
>> @@ -311,8 +311,11 @@ struct vcpu *alloc_vcpu_struct(void)
>> * may require that the shadow CR3 points below 4GB, and hence the whole
>> * structure must satisfy this restriction. Thus we specify
>> MEMF_bits(32).
>> */
>> + unsigned int memflags =
>> + IS_ENABLED(CONFIG_SHADOW_PAGING) ? MEMF_bits(32) : 0;
>
> According to the comment, CONFIG_HVM (or perhaps even
> is_hvm_domain(), if only the corresponding struct domain was
> available here) could be taken into consideration at the same
> time.
is_hvm_domain() would be nice actually. It does look like that should
work: For PV guests, `v->arch.paging.mode` looks like it's set to
`&SHADOW_INTERNAL_NAME(sh_paging_mode, 4)` and never changed [1].
It would be nice if we could test this though.
I'd also be happy to toss this in as-is while we ponder that potential
improvement:
Reviewed-by: George Dunlap <george.dunlap@xxxxxxxxxx>
-George
[1] /build/hg/xen.git/xen/arch/x86/mm/shadow/common.c:shadow_vcpu_init()
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