linux-kernel - Re: [PATCH 4/7] KVM: TDX: restore host xsave state when exit from the guest TD

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <c88ae590-4930-4d22-988c-60a5eeaad490@intel.com>
Date: Mon, 13 Jan 2025 21:28:01 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
Cc: Chao Gao <chao.gao@...el.com>, pbonzini@...hat.com, kvm@...r.kernel.org,
 dave.hansen@...ux.intel.com, rick.p.edgecombe@...el.com,
 kai.huang@...el.com, reinette.chatre@...el.com, xiaoyao.li@...el.com,
 tony.lindgren@...ux.intel.com, binbin.wu@...ux.intel.com,
 dmatlack@...gle.com, isaku.yamahata@...el.com, nik.borisov@...e.com,
 linux-kernel@...r.kernel.org, x86@...nel.org, yan.y.zhao@...el.com,
 weijiang.yang@...el.com
Subject: Re: [PATCH 4/7] KVM: TDX: restore host xsave state when exit from the
 guest TD

On 9/01/25 21:11, Sean Christopherson wrote:
> My vote would to KVM_BUG_ON() before entering the guest.

I notice if KVM_BUG_ON() is called with interrupts disabled
smp_call_function_many_cond() generates a warning:

WARNING: CPU: 223 PID: 4213 at kernel/smp.c:807 smp_call_function_many_cond+0x421/0x560

static void smp_call_function_many_cond(const struct cpumask *mask,
					smp_call_func_t func, void *info,
					unsigned int scf_flags,
					smp_cond_func_t cond_func)
{
	int cpu, last_cpu, this_cpu = smp_processor_id();
	struct call_function_data *cfd;
	bool wait = scf_flags & SCF_WAIT;
	int nr_cpus = 0;
	bool run_remote = false;
	bool run_local = false;

	lockdep_assert_preemption_disabled();

	/*
	 * Can deadlock when called with interrupts disabled.
	 * We allow cpu's that are not yet online though, as no one else can
	 * send smp call function interrupt to this cpu and as such deadlocks
	 * can't happen.
	 */
	if (cpu_online(this_cpu) && !oops_in_progress &&
	    !early_boot_irqs_disabled)
		lockdep_assert_irqs_enabled();			<------------- here

Do we need to care about that?