[PATCH 20/20] KVM: arm64: Don't constrain maximum IPA size based on host configuration

From: Will Deacon <will@kernel.org>
To: kvmarm@lists.cs.columbia.edu
Cc: kernel-team@android.com, Marc Zyngier <maz@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will@kernel.org>,
	linux-arm-kernel@lists.infradead.org
Subject: [PATCH 20/20] KVM: arm64: Don't constrain maximum IPA size based on host configuration
Date: Thu, 30 Jul 2020 16:34:06 +0100	[thread overview]
Message-ID: <20200730153406.25136-21-will@kernel.org> (raw)
In-Reply-To: <20200730153406.25136-1-will@kernel.org>

Now that the guest stage-2 page-tables are managed independently from
the host stage-1 page-tables, we can avoid constraining the IPA size
based on the host and instead limit it only based on the PARange field
of the ID_AA64MMFR0 register.

Cc: Marc Zyngier <maz@kernel.org>
Cc: Quentin Perret <qperret@google.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kvm/reset.c | 38 +++++---------------------------------
 1 file changed, 5 insertions(+), 33 deletions(-)

diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
index 92c3bba048ff..a0c3591286aa 100644
--- a/arch/arm64/kvm/reset.c
+++ b/arch/arm64/kvm/reset.c
@@ -335,7 +335,7 @@ u32 get_kvm_ipa_limit(void)
 
 int kvm_set_ipa_limit(void)
 {
-	unsigned int ipa_max, pa_max, va_max, parange, tgran_2;
+	unsigned int parange, tgran_2;
 	u64 mmfr0;
 
 	mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
@@ -372,38 +372,10 @@ int kvm_set_ipa_limit(void)
 		break;
 	}
 
-	pa_max = id_aa64mmfr0_parange_to_phys_shift(parange);
-
-	/* Clamp the IPA limit to the PA size supported by the kernel */
-	ipa_max = (pa_max > PHYS_MASK_SHIFT) ? PHYS_MASK_SHIFT : pa_max;
-	/*
-	 * Since our stage2 table is dependent on the stage1 page table code,
-	 * we must always honor the following condition:
-	 *
-	 *  Number of levels in Stage1 >= Number of levels in Stage2.
-	 *
-	 * So clamp the ipa limit further down to limit the number of levels.
-	 * Since we can concatenate upto 16 tables at entry level, we could
-	 * go upto 4bits above the maximum VA addressable with the current
-	 * number of levels.
-	 */
-	va_max = PGDIR_SHIFT + PAGE_SHIFT - 3;
-	va_max += 4;
-
-	if (va_max < ipa_max)
-		ipa_max = va_max;
-
-	/*
-	 * If the final limit is lower than the real physical address
-	 * limit of the CPUs, report the reason.
-	 */
-	if (ipa_max < pa_max)
-		pr_info("kvm: Limiting the IPA size due to kernel %s Address limit\n",
-			(va_max < pa_max) ? "Virtual" : "Physical");
-
-	WARN(ipa_max < KVM_PHYS_SHIFT,
-	     "KVM IPA limit (%d bit) is smaller than default size\n", ipa_max);
-	kvm_ipa_limit = ipa_max;
+	kvm_ipa_limit = id_aa64mmfr0_parange_to_phys_shift(parange);
+	WARN(kvm_ipa_limit < KVM_PHYS_SHIFT,
+	     "KVM IPA limit (%d bit) is smaller than default size\n",
+	     kvm_ipa_limit);
 	kvm_info("IPA Size Limit: %dbits\n", kvm_ipa_limit);
 
 	return 0;
-- 
2.28.0.rc0.142.g3c755180ce-goog

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