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SubjectRe: [PATCH RFC v1 06/18] x86/hyperv: allocate output arg pages if required
On Tue, Sep 15, 2020 at 12:16:58PM +0200, Vitaly Kuznetsov wrote:
> Wei Liu <wei.liu@kernel.org> writes:
>
> > When Linux runs as the root partition, it will need to make hypercalls
> > which return data from the hypervisor.
> >
> > Allocate pages for storing results when Linux runs as the root
> > partition.
> >
> > Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> > Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
> > Signed-off-by: Wei Liu <wei.liu@kernel.org>
> > ---
> > arch/x86/hyperv/hv_init.c | 45 +++++++++++++++++++++++++++++----
> > arch/x86/include/asm/mshyperv.h | 1 +
> > 2 files changed, 41 insertions(+), 5 deletions(-)
> >
> > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> > index cac8e4c56261..ebba4be4185d 100644
> > --- a/arch/x86/hyperv/hv_init.c
> > +++ b/arch/x86/hyperv/hv_init.c
> > @@ -45,6 +45,9 @@ EXPORT_SYMBOL_GPL(hv_vp_assist_page);
> > void __percpu **hyperv_pcpu_input_arg;
> > EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
> >
> > +void __percpu **hyperv_pcpu_output_arg;
> > +EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
> > +
> > u32 hv_max_vp_index;
> > EXPORT_SYMBOL_GPL(hv_max_vp_index);
> >
> > @@ -75,14 +78,29 @@ static int hv_cpu_init(unsigned int cpu)
> > u64 msr_vp_index;
> > struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
> > void **input_arg;
> > - struct page *pg;
> > + struct page *input_pg;
> >
> > input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> > /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
> > - pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
> > - if (unlikely(!pg))
> > + input_pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
> > + if (unlikely(!input_pg))
> > return -ENOMEM;
> > - *input_arg = page_address(pg);
> > + *input_arg = page_address(input_pg);
> > +
> > + if (hv_root_partition) {
> > + struct page *output_pg;
> > + void **output_arg;
> > +
> > + output_pg = alloc_page(irqs_disabled() ? GFP_ATOMIC :
> > GFP_KERNEL);
>
> To simplify the code, can we just rename 'input_arg' to 'hypercall_args'
> and do alloc_pages(rqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, 1) to
> allocate two pages above?

It should be doable, but I need to code it up and test it to be 100%
sure.

>
> >
[...]
> > + /* Allocate the per-CPU state for output arg for root */
> > + if (hv_root_partition) {
> > + hyperv_pcpu_output_arg = alloc_percpu(void *);
> redundant space ^^^^^

Fixed. Thanks. This is in fact copied from the input_arg code, so there
is a similar issue there to be fixed. But that's going to wait till
another day.

Wei.

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