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Tue, 17 Nov 2020 10:16:35 -0800 (PST) Date: Tue, 17 Nov 2020 18:15:47 +0000 In-Reply-To: <20201117181607.1761516-1-qperret@google.com> Message-Id: <20201117181607.1761516-8-qperret@google.com> Mime-Version: 1.0 References: <20201117181607.1761516-1-qperret@google.com> X-Mailer: git-send-email 2.29.2.299.gdc1121823c-goog Subject: [RFC PATCH 07/27] KVM: arm64: Introduce a BSS section for use at Hyp From: Quentin Perret To: Catalin Marinas , Will Deacon , Marc Zyngier , James Morse , Julien Thierry , Suzuki K Poulose , Rob Herring , Frank Rowand X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201117_131638_759800_E87B80CD X-CRM114-Status: GOOD ( 16.38 ) 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: "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE" , Quentin Perret , android-kvm@google.com, open list , kernel-team@android.com, "open list:KERNEL VIRTUAL MACHINE FOR ARM64 \(KVM/arm64\)" , "moderated list:ARM64 PORT \(AARCH64 ARCHITECTURE\)" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Currently, the hyp code cannot make full use of a bss, as the kernel section is mapped read-only. While this mapping could simply be changed to read-write, it would intermingle even more the hyp and kernel state than they currently are. Instead, introduce a __hyp_bss section, that uses reserved pages, and create the appropriate RW hyp mappings during KVM init. Signed-off-by: Quentin Perret --- arch/arm64/include/asm/sections.h | 1 + arch/arm64/kernel/vmlinux.lds.S | 7 +++++++ arch/arm64/kvm/arm.c | 11 +++++++++++ arch/arm64/kvm/hyp/nvhe/hyp.lds.S | 1 + 4 files changed, 20 insertions(+) diff --git a/arch/arm64/include/asm/sections.h b/arch/arm64/include/asm/sections.h index 8ff579361731..f58cf493de16 100644 --- a/arch/arm64/include/asm/sections.h +++ b/arch/arm64/include/asm/sections.h @@ -12,6 +12,7 @@ extern char __hibernate_exit_text_start[], __hibernate_exit_text_end[]; extern char __hyp_idmap_text_start[], __hyp_idmap_text_end[]; extern char __hyp_text_start[], __hyp_text_end[]; extern char __hyp_data_ro_after_init_start[], __hyp_data_ro_after_init_end[]; +extern char __hyp_bss_start[], __hyp_bss_end[]; extern char __idmap_text_start[], __idmap_text_end[]; extern char __initdata_begin[], __initdata_end[]; extern char __inittext_begin[], __inittext_end[]; diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 4382b5d0645d..ded78a25365d 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -8,6 +8,13 @@ #define RO_EXCEPTION_TABLE_ALIGN 8 #define RUNTIME_DISCARD_EXIT +#define BSS_FIRST_SECTIONS \ + . = ALIGN(PAGE_SIZE); \ + __hyp_bss_start = .; \ + *(.hyp.bss) \ + . = ALIGN(PAGE_SIZE); \ + __hyp_bss_end = .; + #include #include #include diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 7335eb4fb0bd..882eb383bd75 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -1709,7 +1709,18 @@ static int init_hyp_mode(void) goto out_err; } + /* + * .hyp.bss is placed at the beginning of the .bss section, so map that + * part RW, and the rest RO as the hyp shouldn't be touching it. + */ err = create_hyp_mappings(kvm_ksym_ref(__bss_start), + kvm_ksym_ref(__hyp_bss_end), PAGE_HYP); + if (err) { + kvm_err("Cannot map hyp bss section: %d\n", err); + goto out_err; + } + + err = create_hyp_mappings(kvm_ksym_ref(__hyp_bss_end), kvm_ksym_ref(__bss_stop), PAGE_HYP_RO); if (err) { kvm_err("Cannot map bss section\n"); diff --git a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S index 5d76ff2ba63e..dc281d90063e 100644 --- a/arch/arm64/kvm/hyp/nvhe/hyp.lds.S +++ b/arch/arm64/kvm/hyp/nvhe/hyp.lds.S @@ -17,4 +17,5 @@ SECTIONS { PERCPU_INPUT(L1_CACHE_BYTES) } HYP_SECTION(.data..ro_after_init) + HYP_SECTION(.bss) }