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Mon, 16 Nov 2020 01:24:58 -0800 (PST) Date: Mon, 16 Nov 2020 09:24:57 +0000 From: David Brazdil To: Jamie Iles Subject: Re: [PATCH] kvm: arm64: correctly align nVHE percpu data Message-ID: <20201116092457.5k2eyynllsgi4fpg@google.com> References: <20201113101227.zb6ckyriobjrlkc5@google.com> <20201113150406.14314-1-jamie@nuviainc.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201113150406.14314-1-jamie@nuviainc.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201116_042501_755913_5BB67CAB X-CRM114-Status: GOOD ( 23.69 ) 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: Marc Zyngier , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Thanks Jamie On Fri, Nov 13, 2020 at 03:04:06PM +0000, Jamie Iles wrote: > The nVHE percpu data is partially linked but the nVHE linker script did > not align the percpu section. The PERCPU_INPUT macro would then align > the data to a page boundary: > > #define PERCPU_INPUT(cacheline) \ > __per_cpu_start = .; \ > *(.data..percpu..first) \ > . = ALIGN(PAGE_SIZE); \ > *(.data..percpu..page_aligned) \ > . = ALIGN(cacheline); \ > *(.data..percpu..read_mostly) \ > . = ALIGN(cacheline); \ > *(.data..percpu) \ > *(.data..percpu..shared_aligned) \ > PERCPU_DECRYPTED_SECTION \ > __per_cpu_end = .; > > but then when the final vmlinux linking happens the hypervisor percpu > data is included after page alignment and so the offsets potentially > don't match. On my build I saw that the .hyp.data..percpu section was > at address 0x20 and then the percpu data would begin at 0x1000 (because > of the page alignment in PERCPU_INPUT), but when linked into vmlinux, > everything would be shifted down by 0x20 bytes. > > This manifests as one of the CPUs getting lost when running > kvm-unit-tests or starting any VM and subsequent soft lockup on a Cortex > A72 device. > > Fixes: 30c953911c43 ("kvm: arm64: Set up hyp percpu data for nVHE") > Cc: David Brazdil > Cc: Marc Zyngier > Cc: Will Deacon Acked-by: David Brazdil > Signed-off-by: Jamie Iles > --- > v2: add clarifying commentary > > arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S > index bb2d986ff696..a797abace13f 100644 > --- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S > +++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S > @@ -13,6 +13,11 @@ > > SECTIONS { > HYP_SECTION(.text) > + /* > + * .hyp..data..percpu needs to be page aligned to maintain the same > + * alignment for when linking into vmlinux. > + */ > + . = ALIGN(PAGE_SIZE); > HYP_SECTION_NAME(.data..percpu) : { > PERCPU_INPUT(L1_CACHE_BYTES) > } > -- > 2.27.0 > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel