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From:   Steven Price <steven.price@arm.com>
To:     Catalin Marinas <catalin.marinas@arm.com>,
        Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>
Cc:     Steven Price <steven.price@arm.com>,
        James Morse <james.morse@arm.com>,
        Julien Thierry <julien.thierry.kdev@gmail.com>,
        Suzuki K Poulose <suzuki.poulose@arm.com>,
        kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org,
        Alexander Potapenko <glider@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Andrey Konovalov <andreyknvl@google.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>
Subject: [PATCH] KVM: arm64: Compute TPIDR_EL2 ignoring MTE tag
Date:   Fri,  8 Jan 2021 16:12:54 +0000
Message-Id: <20210108161254.53674-1-steven.price@arm.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

KASAN in HW_TAGS mode will store MTE tags in the top byte of the
pointer. When computing the offset for TPIDR_EL2 we don't want anything
in the top byte, so remove the tag to ensure the computation is correct
no matter what the tag.

Fixes: 94ab5b61ee16 ("kasan, arm64: enable CONFIG_KASAN_HW_TAGS")
Signed-off-by: Steven Price <steven.price@arm.com>
---
Without this fix I can't boot a config with KASAN_HW_TAGS and KVM on an
MTE enabled host. I'm unsure if this should really be in
this_cpu_ptr_nvhe_sym().

 arch/arm64/kvm/arm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 6e637d2b4cfb..3783082148bc 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1403,7 +1403,7 @@ static void cpu_init_hyp_mode(void)
 	 * kernel's mapping to the linear mapping, and store it in tpidr_el2
 	 * so that we can use adr_l to access per-cpu variables in EL2.
 	 */
-	params->tpidr_el2 = (unsigned long)this_cpu_ptr_nvhe_sym(__per_cpu_start) -
+	params->tpidr_el2 = (unsigned long)kasan_reset_tag(this_cpu_ptr_nvhe_sym(__per_cpu_start)) -
 			    (unsigned long)kvm_ksym_ref(CHOOSE_NVHE_SYM(__per_cpu_start));
 
 	params->mair_el2 = read_sysreg(mair_el1);
-- 
2.20.1