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SubjectRe: [PATCH RFC v1 06/18] x86/hyperv: allocate output arg pages if required
Date
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?

> + if (unlikely(!output_pg)) {
> + free_page((unsigned long)*input_arg);
> + *input_arg = NULL;
> + return -ENOMEM;
> + }
> +
> + output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> + *output_arg = page_address(output_pg);
> + }
>
> hv_get_vp_index(msr_vp_index);
>
> @@ -209,14 +227,25 @@ static int hv_cpu_die(unsigned int cpu)
> unsigned int new_cpu;
> unsigned long flags;
> void **input_arg;
> - void *input_pg = NULL;
> + void *input_pg = NULL, *output_pg = NULL;
>
> local_irq_save(flags);
> input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
> input_pg = *input_arg;
> *input_arg = NULL;
> +
> + if (hv_root_partition) {
> + void **output_arg;
> +
> + output_arg = (void **)this_cpu_ptr(hyperv_pcpu_output_arg);
> + output_pg = *output_arg;
> + *output_arg = NULL;
> + }
> +
> local_irq_restore(flags);
> +
> free_page((unsigned long)input_pg);
> + free_page((unsigned long)output_pg);
>
> if (hv_vp_assist_page && hv_vp_assist_page[cpu])
> wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);
> @@ -350,6 +379,12 @@ void __init hyperv_init(void)
>
> BUG_ON(hyperv_pcpu_input_arg == NULL);
>
> + /* Allocate the per-CPU state for output arg for root */
> + if (hv_root_partition) {
> + hyperv_pcpu_output_arg = alloc_percpu(void *);
redundant space ^^^^^

> + BUG_ON(hyperv_pcpu_output_arg == NULL);
> + }
> +
> /* Allocate percpu VP index */
> hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
> GFP_KERNEL);
> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
> index 2a2cc81beac6..f5c62140f28d 100644
> --- a/arch/x86/include/asm/mshyperv.h
> +++ b/arch/x86/include/asm/mshyperv.h
> @@ -63,6 +63,7 @@ static inline void hv_disable_stimer0_percpu_irq(int irq) {}
> #if IS_ENABLED(CONFIG_HYPERV)
> extern void *hv_hypercall_pg;
> extern void __percpu **hyperv_pcpu_input_arg;
> +extern void __percpu **hyperv_pcpu_output_arg;
>
> static inline u64 hv_do_hypercall(u64 control, void *input, void *output)
> {

--
Vitaly

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