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SubjectRe: [PATCH v4 10/10] arm64: Retrieve stolen time as paravirtualized guest
On Fri, Aug 30, 2019 at 09:42:55AM +0100, Steven Price wrote:
> Enable paravirtualization features when running under a hypervisor
> supporting the PV_TIME_ST hypercall.
>
> For each (v)CPU, we ask the hypervisor for the location of a shared
> page which the hypervisor will use to report stolen time to us. We set
> pv_time_ops to the stolen time function which simply reads the stolen
> value from the shared page for a VCPU. We guarantee single-copy
> atomicity using READ_ONCE which means we can also read the stolen
> time for another VCPU than the currently running one while it is
> potentially being updated by the hypervisor.
>
> Signed-off-by: Steven Price <steven.price@arm.com>
> ---
> arch/arm64/include/asm/paravirt.h | 9 +-
> arch/arm64/kernel/paravirt.c | 148 ++++++++++++++++++++++++++++++
> arch/arm64/kernel/time.c | 3 +
> include/linux/cpuhotplug.h | 1 +
> 4 files changed, 160 insertions(+), 1 deletion(-)
>
> diff --git a/arch/arm64/include/asm/paravirt.h b/arch/arm64/include/asm/paravirt.h
> index 799d9dd6f7cc..125c26c42902 100644
> --- a/arch/arm64/include/asm/paravirt.h
> +++ b/arch/arm64/include/asm/paravirt.h
> @@ -21,6 +21,13 @@ static inline u64 paravirt_steal_clock(int cpu)
> {
> return pv_ops.time.steal_clock(cpu);
> }
> -#endif
> +
> +int __init kvm_guest_init(void);
> +
> +#else
> +
> +#define kvm_guest_init()
> +
> +#endif // CONFIG_PARAVIRT
>
> #endif
> diff --git a/arch/arm64/kernel/paravirt.c b/arch/arm64/kernel/paravirt.c
> index 4cfed91fe256..5bf3be7ccf7e 100644
> --- a/arch/arm64/kernel/paravirt.c
> +++ b/arch/arm64/kernel/paravirt.c
> @@ -6,13 +6,161 @@
> * Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> */
>
> +#define pr_fmt(fmt) "kvmarm-pv: " fmt
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/cpuhotplug.h>
> #include <linux/export.h>
> +#include <linux/io.h>
> #include <linux/jump_label.h>
> +#include <linux/printk.h>
> +#include <linux/psci.h>
> +#include <linux/reboot.h>
> +#include <linux/slab.h>
> #include <linux/types.h>
> +
> #include <asm/paravirt.h>
> +#include <asm/pvclock-abi.h>
> +#include <asm/smp_plat.h>
>
> struct static_key paravirt_steal_enabled;
> struct static_key paravirt_steal_rq_enabled;
>
> struct paravirt_patch_template pv_ops;
> EXPORT_SYMBOL_GPL(pv_ops);
> +
> +struct kvmarm_stolen_time_region {
> + struct pvclock_vcpu_stolen_time *kaddr;
> +};
> +
> +static DEFINE_PER_CPU(struct kvmarm_stolen_time_region, stolen_time_region);
> +
> +static bool steal_acc = true;
> +static int __init parse_no_stealacc(char *arg)
> +{
> + steal_acc = false;
> + return 0;
> +}
> +
> +early_param("no-steal-acc", parse_no_stealacc);

Need to also add an 'ARM64' to the
Documentation/admin-guide/kernel-parameters.txt entry for this.

Thanks,
drew

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