KVM Archive on lore.kernel.org
 help / color / Atom feed
From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Haiwei Li <lihaiwei.kernel@gmail.com>
Cc: "pbonzini\@redhat.com" <pbonzini@redhat.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	"wanpengli\@tencent.com" <wanpengli@tencent.com>,
	"jmattson\@google.com" <jmattson@google.com>,
	"joro\@8bytes.org" <joro@8bytes.org>,
	tglx@linutronix.de, mingo@redhat.com,
	"bp\@alien8.de" <bp@alien8.de>, "hpa\@zytor.com" <hpa@zytor.com>,
	"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kvm\@vger.kernel.org" <kvm@vger.kernel.org>,
	"x86\@kernel.org" <x86@kernel.org>
Subject: Re: [PATCH v2] KVM: Check the allocation of pv cpu mask
Date: Thu, 03 Sep 2020 12:39:52 +0200
Message-ID: <87y2lrnnyf.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <654d8c60-49f0-e398-be25-24aed352360d@gmail.com>

Haiwei Li <lihaiwei.kernel@gmail.com> writes:

> From: Haiwei Li <lihaiwei@tencent.com>
>
> check the allocation of per-cpu __pv_cpu_mask. Initialize ops only when
> successful.
>
> Signed-off-by: Haiwei Li <lihaiwei@tencent.com>
> ---
>   arch/x86/kernel/kvm.c | 24 ++++++++++++++++++++----
>   1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 08320b0b2b27..d3c062e551d7 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -555,7 +555,6 @@ static void kvm_send_ipi_mask_allbutself(const 
> struct cpumask *mask, int vector)
>   static void kvm_setup_pv_ipi(void)
>   {
>   	apic->send_IPI_mask = kvm_send_ipi_mask;
> -	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
>   	pr_info("setup PV IPIs\n");
>   }
>
> @@ -654,7 +653,6 @@ static void __init kvm_guest_init(void)
>   	}
>
>   	if (pv_tlb_flush_supported()) {
> -		pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
>   		pv_ops.mmu.tlb_remove_table = tlb_remove_table;
>   		pr_info("KVM setup pv remote TLB flush\n");
>   	}
> @@ -767,6 +765,14 @@ static __init int activate_jump_labels(void)
>   }
>   arch_initcall(activate_jump_labels);
>
> +static void kvm_free_pv_cpu_mask(void)
> +{
> +	unsigned int cpu;
> +
> +	for_each_possible_cpu(cpu)
> +		free_cpumask_var(per_cpu(__pv_cpu_mask, cpu));
> +}
> +
>   static __init int kvm_alloc_cpumask(void)
>   {
>   	int cpu;
> @@ -785,11 +791,21 @@ static __init int kvm_alloc_cpumask(void)
>
>   	if (alloc)
>   		for_each_possible_cpu(cpu) {
> -			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
> -				GFP_KERNEL, cpu_to_node(cpu));
> +			if (!zalloc_cpumask_var_node(
> +				per_cpu_ptr(&__pv_cpu_mask, cpu),
> +				GFP_KERNEL, cpu_to_node(cpu)))
> +				goto zalloc_cpumask_fail;
>   		}
>
> +#if defined(CONFIG_SMP)
> +	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
> +#endif
> +	pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;

This is too late I'm afraid. If I'm not mistaken PV patching happens
earlier, so .init.guest_late_init (kvm_guest_init()) is good and
arch_initcall() is bad.

Have you checked that with this patch kvm_flush_tlb_others() is still
being called?

Actually, there is no need to assign kvm_flush_tlb_others() so late. We
can always check if __pv_cpu_mask was allocated and revert back to the
architectural path if not.

>   	return 0;
> +
> +zalloc_cpumask_fail:
> +	kvm_free_pv_cpu_mask();
> +	return -ENOMEM;
>   }
>   arch_initcall(kvm_alloc_cpumask);
>
> --
> 2.18.4
>

-- 
Vitaly


  reply index

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-03  1:59 Haiwei Li
2020-09-03 10:39 ` Vitaly Kuznetsov [this message]
2020-09-04  1:01   ` Haiwei Li
2020-09-04  9:53     ` Vitaly Kuznetsov
2020-09-04 12:21       ` Haiwei Li

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87y2lrnnyf.fsf@vitty.brq.redhat.com \
    --to=vkuznets@redhat.com \
    --cc=bp@alien8.de \
    --cc=hpa@zytor.com \
    --cc=jmattson@google.com \
    --cc=joro@8bytes.org \
    --cc=kvm@vger.kernel.org \
    --cc=lihaiwei.kernel@gmail.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@redhat.com \
    --cc=pbonzini@redhat.com \
    --cc=sean.j.christopherson@intel.com \
    --cc=tglx@linutronix.de \
    --cc=wanpengli@tencent.com \
    --cc=x86@kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

KVM Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/kvm/0 kvm/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 kvm kvm/ https://lore.kernel.org/kvm \
		kvm@vger.kernel.org
	public-inbox-index kvm

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.kvm


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git