From: Peter Zijlstra <peterz@infradead.org>
To: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Dimitri John Ledkov <dimitri.ledkov@canonical.com>,
Borislav Petkov <bp@suse.de>,
stable@vger.kernel.org
Subject: Re: [PATCH] x86/bugs: Do not enable IBPB at firmware entry when IBPB is not available
Date: Thu, 28 Jul 2022 17:16:40 +0200 [thread overview]
Message-ID: <YuKoWPRt56T+FE+s@worktop.programming.kicks-ass.net> (raw)
In-Reply-To: <20220728122602.2500509-1-cascardo@canonical.com>
On Thu, Jul 28, 2022 at 09:26:02AM -0300, Thadeu Lima de Souza Cascardo wrote:
> Some cloud hypervisors do not provide IBPB on very recent CPU processors,
> including AMD processors affected by Retbleed.
That's a bug in the hypervisor.
> Fixes: 28a99e95f55c ("x86/amd: Use IBPB for firmware calls")
Fixes^WCreates-a-speculation-hole-in:
> Reported-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
> Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
> Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
> Cc: Borislav Petkov <bp@suse.de>
> Cc: <stable@vger.kernel.org>
> ---
> arch/x86/kernel/cpu/bugs.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
> index 6454bc767f0f..6761668100b9 100644
> --- a/arch/x86/kernel/cpu/bugs.c
> +++ b/arch/x86/kernel/cpu/bugs.c
> @@ -1520,6 +1520,7 @@ static void __init spectre_v2_select_mitigation(void)
> * enable IBRS around firmware calls.
> */
> if (boot_cpu_has_bug(X86_BUG_RETBLEED) &&
> + boot_cpu_has(X86_FEATURE_IBPB) &&
> (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
> boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) {
At the very least we need a pr_warn() and something nasty in
retbleed_show_state() to warn the user their firmware calls are
vulnerable.
next prev parent reply other threads:[~2022-07-28 15:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-28 12:26 [PATCH] x86/bugs: Do not enable IBPB at firmware entry when IBPB is not available Thadeu Lima de Souza Cascardo
2022-07-28 12:35 ` Borislav Petkov
2022-07-28 12:39 ` Thadeu Lima de Souza Cascardo
2022-07-28 14:33 ` Dimitri John Ledkov
2022-07-28 15:18 ` Borislav Petkov
2022-07-28 15:50 ` Borislav Petkov
2022-07-28 17:01 ` Thadeu Lima de Souza Cascardo
2022-07-29 18:22 ` Borislav Petkov
2022-07-28 15:16 ` Peter Zijlstra [this message]
2022-07-29 8:11 ` [tip: x86/urgent] " tip-bot2 for Thadeu Lima de Souza Cascardo
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