From: Marc Zyngier <maz@kernel.org>
To: Thomas Tai <thomas.tai@oracle.com>
Cc: kvmarm@lists.cs.columbia.edu, james.morse@arm.com,
linux-arm-kernel@lists.infradead.org,
julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com
Subject: Re: [PATCH] KVM: arm64: Fixes ARM VM hangs at boot
Date: Thu, 01 Oct 2020 09:30:58 +0100 [thread overview]
Message-ID: <f906ecd23609bbdf4a1db991624943d5@kernel.org> (raw)
In-Reply-To: <20200930221239.488744-1-thomas.tai@oracle.com>
Hi Thomas,
On 2020-09-30 23:12, Thomas Tai wrote:
> When using the latest kernel v5.9-rc7 on an ARM server, VMs could
> hang at boot with no output. The commit a0e50aa3f4a8 removed
> asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT)),
> it looks like isb is still needed for non
> ARM64_WORKAROUND_SPECULATIVE_AT host when switching to guest.
Is that on an eMAG system, by any chance?
>
> The code fragment for the original patch:
> - /* __load_guest_stage2() includes an ISB for the workaround. */
> - __load_guest_stage2(kvm);
> - asm(ALTERNATIVE("isb", "nop",
> ARM64_WORKAROUND_SPECULATIVE_AT));
> + __load_guest_stage2(mmu);
>
> The code should have been:
> - /* __load_guest_stage2() includes an ISB for the workaround. */
> - __load_guest_stage2(kvm);
> - asm(ALTERNATIVE("isb", "nop",
> ARM64_WORKAROUND_SPECULATIVE_AT));
> + __load_guest_stage2(mmu);
> + asm(ALTERNATIVE("isb", "nop",
> ARM64_WORKAROUND_SPECULATIVE_AT));
> ie, the workaround is still needed.
>
> Fixes: a0e50aa3f4a8 ("KVM: arm64: Factor out stage 2 page table data
> from
> struct kvm")
>
> Signed-off-by: Thomas Tai <thomas.tai@oracle.com>
> ---
> arch/arm64/kvm/hyp/nvhe/tlb.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/tlb.c
> b/arch/arm64/kvm/hyp/nvhe/tlb.c
> index 69eae60..536496e 100644
> --- a/arch/arm64/kvm/hyp/nvhe/tlb.c
> +++ b/arch/arm64/kvm/hyp/nvhe/tlb.c
> @@ -32,6 +32,7 @@ static void __tlb_switch_to_guest(struct kvm_s2_mmu
> *mmu,
> }
>
> __load_guest_stage2(mmu);
> + asm(ALTERNATIVE("isb", "nop", ARM64_WORKAROUND_SPECULATIVE_AT));
> }
>
> static void __tlb_switch_to_host(struct tlb_inv_context *cxt)
Ouch. I remember fixing this a while ago, but somehow dropped it
after applying it and *not* merging it...
Thanks a lot for the heads up!
M.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/pre-nv-5.9
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-10-01 8:32 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-30 22:12 [PATCH] KVM: arm64: Fixes ARM VM hangs at boot Thomas Tai
2020-10-01 8:30 ` Marc Zyngier [this message]
2020-10-01 12:59 ` Thomas Tai
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