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Thu, 01 Oct 2020 09:30:58 +0100 MIME-Version: 1.0 Date: Thu, 01 Oct 2020 09:30:58 +0100 From: Marc Zyngier To: Thomas Tai Subject: Re: [PATCH] KVM: arm64: Fixes ARM VM hangs at boot In-Reply-To: <20200930221239.488744-1-thomas.tai@oracle.com> References: <20200930221239.488744-1-thomas.tai@oracle.com> User-Agent: Roundcube Webmail/1.4.8 Message-ID: X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: thomas.tai@oracle.com, james.morse@arm.com, julien.thierry.kdev@gmail.com, suzuki.poulose@arm.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201001_043101_452347_2027C4DF X-CRM114-Status: GOOD ( 22.50 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , 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 Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org 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 > --- > 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... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel