linux-kernel - Re: [PATCH 04/12] x86/xen: add system core suspend and resume callbacks

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Date:   Sat, 30 May 2020 19:10:04 -0400
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     Anchal Agarwal <anchalag@...zon.com>, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, hpa@...or.com, x86@...nel.org,
        jgross@...e.com, linux-pm@...r.kernel.org, linux-mm@...ck.org,
        kamatam@...zon.com, sstabellini@...nel.org, konrad.wilk@...cle.com,
        roger.pau@...rix.com, axboe@...nel.dk, davem@...emloft.net,
        rjw@...ysocki.net, len.brown@...el.com, pavel@....cz,
        peterz@...radead.org, eduval@...zon.com, sblbir@...zon.com,
        xen-devel@...ts.xenproject.org, vkuznets@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        dwmw@...zon.co.uk, benh@...nel.crashing.org
Subject: Re: [PATCH 04/12] x86/xen: add system core suspend and resume
 callbacks

On 5/19/20 7:26 PM, Anchal Agarwal wrote:
> From: Munehisa Kamata <kamatam@...zon.com>
>
> Add Xen PVHVM specific system core callbacks for PM suspend and
> hibernation support. The callbacks suspend and resume Xen
> primitives,like shared_info, pvclock and grant table. Note that
> Xen suspend can handle them in a different manner, but system
> core callbacks are called from the context.


I don't think I understand that last sentence.


>  So if the callbacks
> are called from Xen suspend context, return immediately.
>


> +
> +static int xen_syscore_suspend(void)
> +{
> +	struct xen_remove_from_physmap xrfp;
> +	int ret;
> +
> +	/* Xen suspend does similar stuffs in its own logic */
> +	if (xen_suspend_mode_is_xen_suspend())
> +		return 0;
> +
> +	xrfp.domid = DOMID_SELF;
> +	xrfp.gpfn = __pa(HYPERVISOR_shared_info) >> PAGE_SHIFT;
> +
> +	ret = HYPERVISOR_memory_op(XENMEM_remove_from_physmap, &xrfp);
> +	if (!ret)
> +		HYPERVISOR_shared_info = &xen_dummy_shared_info;
> +
> +	return ret;
> +}
> +
> +static void xen_syscore_resume(void)
> +{
> +	/* Xen suspend does similar stuffs in its own logic */
> +	if (xen_suspend_mode_is_xen_suspend())
> +		return;
> +
> +	/* No need to setup vcpu_info as it's already moved off */
> +	xen_hvm_map_shared_info();
> +
> +	pvclock_resume();
> +
> +	gnttab_resume();


Do you call gnttab_suspend() in pm suspend path?


> +}
> +
> +/*
> + * These callbacks will be called with interrupts disabled and when having only
> + * one CPU online.
> + */
> +static struct syscore_ops xen_hvm_syscore_ops = {
> +	.suspend = xen_syscore_suspend,
> +	.resume = xen_syscore_resume
> +};
> +
> +void __init xen_setup_syscore_ops(void)
> +{
> +	if (xen_hvm_domain())


Have you tested this (the whole feature, not just this patch) with PVH
guest BTW? And PVH dom0 for that matter?


-boris


> +		register_syscore_ops(&xen_hvm_syscore_ops);
> +}