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[85.244.65.113]) by mx.google.com with ESMTPSA id q10sm1846563wjr.41.2015.02.26.07.29.16 (version=TLSv1.1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 26 Feb 2015 07:29:17 -0800 (PST) From: Ard Biesheuvel To: will.deacon@arm.com, mark.rutland@arm.com, marc.zyngier@arm.com, linux-arm-kernel@lists.infradead.org, catalin.marinas@arm.com, steve.capper@linaro.org, christoffer.dall@linaro.org Subject: [RFC PATCH 1/3] ARM, arm64: kvm: get rid of the bounce page Date: Thu, 26 Feb 2015 15:29:05 +0000 Message-Id: <1424964547-2118-2-git-send-email-ard.biesheuvel@linaro.org> X-Mailer: git-send-email 1.8.3.2 In-Reply-To: <1424964547-2118-1-git-send-email-ard.biesheuvel@linaro.org> References: <1424964547-2118-1-git-send-email-ard.biesheuvel@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150226_072940_977618_5B60F49B X-CRM114-Status: GOOD ( 21.74 ) X-Spam-Score: -0.7 (/) X-Spam-Report: SpamAssassin version 3.4.0 on bombadil.infradead.org summary: Content analysis details: (-0.7 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.7 RCVD_IN_DNSWL_LOW RBL: Sender listed at http://www.dnswl.org/, low trust [74.125.82.42 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H3 RBL: Good reputation (+3) [74.125.82.42 listed in wl.mailspike.net] -0.0 SPF_PASS SPF: sender matches SPF record -0.0 RCVD_IN_MSPIKE_WL Mailspike good senders Cc: Ard Biesheuvel X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: , List-Help: , List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patch=linaro.org@lists.infradead.org X-Removed-Original-Auth: Dkim didn't pass. X-Original-Sender: ard.biesheuvel@linaro.org X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of patch+caf_=patchwork-forward=linaro.org@linaro.org designates 209.85.217.178 as permitted sender) smtp.mail=patch+caf_=patchwork-forward=linaro.org@linaro.org Mailing-list: list patchwork-forward@linaro.org; contact patchwork-forward+owners@linaro.org X-Google-Group-Id: 836684582541 The HYP init bounce page is a runtime construct that ensures that the HYP init code does not cross a page boundary. However, this is something we can do perfectly well at build time, by aligning the code appropriately. For arm64, we just align to 4 KB, and enforce that the code size is less than 4 KB, regardless of the chosen page size. For ARM, the whole code is less than 256 bytes, so we tweak the linker script to align at a power of 2 upper bound of the code size Note that this also fixes a benign off-by-one error in the original bounce page code, where a bounce page would be allocated unnecessarily if the code was exactly 1 page in size. Signed-off-by: Ard Biesheuvel --- arch/arm/kernel/vmlinux.lds.S | 12 +++++++++--- arch/arm/kvm/init.S | 11 +++++++++++ arch/arm/kvm/mmu.c | 42 +++++------------------------------------ arch/arm64/kernel/vmlinux.lds.S | 18 ++++++++++++------ 4 files changed, 37 insertions(+), 46 deletions(-) diff --git a/arch/arm/kernel/vmlinux.lds.S b/arch/arm/kernel/vmlinux.lds.S index b31aa73e8076..8179d3903dee 100644 --- a/arch/arm/kernel/vmlinux.lds.S +++ b/arch/arm/kernel/vmlinux.lds.S @@ -23,7 +23,7 @@ VMLINUX_SYMBOL(__idmap_text_start) = .; \ *(.idmap.text) \ VMLINUX_SYMBOL(__idmap_text_end) = .; \ - . = ALIGN(32); \ + . = ALIGN(1 << __hyp_idmap_align_order); \ VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \ *(.hyp.idmap.text) \ VMLINUX_SYMBOL(__hyp_idmap_text_end) = .; @@ -346,8 +346,14 @@ SECTIONS */ ASSERT((__proc_info_end - __proc_info_begin), "missing CPU support") ASSERT((__arch_info_end - __arch_info_begin), "no machine record defined") + /* - * The HYP init code can't be more than a page long. + * The HYP init code can't be more than a page long, + * and should not cross a page boundary. * The above comment applies as well. */ -ASSERT(((__hyp_idmap_text_end - __hyp_idmap_text_start) <= PAGE_SIZE), "HYP init code too big") +ASSERT(((__hyp_idmap_text_end - 1) & PAGE_MASK) - + (__hyp_idmap_text_start & PAGE_MASK) == 0, + "HYP init code too big or unaligned") +ASSERT(__hyp_idmap_size <= (1 << __hyp_idmap_align_order), + "__hyp_idmap_size should be <= (1 << __hyp_idmap_align_order)") diff --git a/arch/arm/kvm/init.S b/arch/arm/kvm/init.S index 3988e72d16ff..7a279bc8e0e1 100644 --- a/arch/arm/kvm/init.S +++ b/arch/arm/kvm/init.S @@ -157,3 +157,14 @@ target: @ We're now in the trampoline code, switch page tables __kvm_hyp_init_end: .popsection + + /* + * When making changes to this file, make sure that the value of + * __hyp_idmap_align_order is updated if the size of the code ends up + * exceeding (1 << __hyp_idmap_align_order). This helps ensure that the + * code never crosses a page boundary, without wasting too much memory + * on aligning to PAGE_SIZE. + */ + .global __hyp_idmap_size, __hyp_idmap_align_order + .set __hyp_idmap_size, __kvm_hyp_init_end - __kvm_hyp_init + .set __hyp_idmap_align_order, 8 diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c index 3e6859bc3e11..42a24d6b003b 100644 --- a/arch/arm/kvm/mmu.c +++ b/arch/arm/kvm/mmu.c @@ -37,7 +37,6 @@ static pgd_t *boot_hyp_pgd; static pgd_t *hyp_pgd; static DEFINE_MUTEX(kvm_hyp_pgd_mutex); -static void *init_bounce_page; static unsigned long hyp_idmap_start; static unsigned long hyp_idmap_end; static phys_addr_t hyp_idmap_vector; @@ -405,9 +404,6 @@ void free_boot_hyp_pgd(void) if (hyp_pgd) unmap_range(NULL, hyp_pgd, TRAMPOLINE_VA, PAGE_SIZE); - free_page((unsigned long)init_bounce_page); - init_bounce_page = NULL; - mutex_unlock(&kvm_hyp_pgd_mutex); } @@ -1498,39 +1494,11 @@ int kvm_mmu_init(void) hyp_idmap_end = kvm_virt_to_phys(__hyp_idmap_text_end); hyp_idmap_vector = kvm_virt_to_phys(__kvm_hyp_init); - if ((hyp_idmap_start ^ hyp_idmap_end) & PAGE_MASK) { - /* - * Our init code is crossing a page boundary. Allocate - * a bounce page, copy the code over and use that. - */ - size_t len = __hyp_idmap_text_end - __hyp_idmap_text_start; - phys_addr_t phys_base; - - init_bounce_page = (void *)__get_free_page(GFP_KERNEL); - if (!init_bounce_page) { - kvm_err("Couldn't allocate HYP init bounce page\n"); - err = -ENOMEM; - goto out; - } - - memcpy(init_bounce_page, __hyp_idmap_text_start, len); - /* - * Warning: the code we just copied to the bounce page - * must be flushed to the point of coherency. - * Otherwise, the data may be sitting in L2, and HYP - * mode won't be able to observe it as it runs with - * caches off at that point. - */ - kvm_flush_dcache_to_poc(init_bounce_page, len); - - phys_base = kvm_virt_to_phys(init_bounce_page); - hyp_idmap_vector += phys_base - hyp_idmap_start; - hyp_idmap_start = phys_base; - hyp_idmap_end = phys_base + len; - - kvm_info("Using HYP init bounce page @%lx\n", - (unsigned long)phys_base); - } + /* + * We rely on the linker script to ensure at build time that the HYP + * init code does not cross a page boundary. + */ + BUG_ON((hyp_idmap_start ^ (hyp_idmap_end - 1)) & PAGE_MASK); hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order); boot_hyp_pgd = (pgd_t *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, hyp_pgd_order); diff --git a/arch/arm64/kernel/vmlinux.lds.S b/arch/arm64/kernel/vmlinux.lds.S index 5d9d2dca530d..17383c257a7d 100644 --- a/arch/arm64/kernel/vmlinux.lds.S +++ b/arch/arm64/kernel/vmlinux.lds.S @@ -23,10 +23,14 @@ jiffies = jiffies_64; #define HYPERVISOR_TEXT \ /* \ - * Force the alignment to be compatible with \ - * the vectors requirements \ + * Align to 4K so that \ + * a) the HYP vector table is at its minimum \ + * alignment of 2048 bytes \ + * b) the HYP init code will not cross a page \ + * boundary if its size does not exceed \ + * 4K (see related ASSERT() below) \ */ \ - . = ALIGN(2048); \ + . = ALIGN(SZ_4K); \ VMLINUX_SYMBOL(__hyp_idmap_text_start) = .; \ *(.hyp.idmap.text) \ VMLINUX_SYMBOL(__hyp_idmap_text_end) = .; \ @@ -163,10 +167,12 @@ SECTIONS } /* - * The HYP init code can't be more than a page long. + * The HYP init code can't be more than a page long, + * and should not cross a page boundary. */ -ASSERT(((__hyp_idmap_text_start + PAGE_SIZE) > __hyp_idmap_text_end), - "HYP init code too big") +ASSERT(((__hyp_idmap_text_end - 1) & ~(SZ_4K - 1)) - + (__hyp_idmap_text_start & ~(SZ_4K - 1)) == 0, + "HYP init code too big or unaligned") /* * If padding is applied before .head.text, virt<->phys conversions will fail.