[RFC PATCH v2 07/26] KVM: arm64: Introduce a BSS section for use at Hyp
From: Quentin Perret <hidden>
Date: 2021-01-08 12:17:23
Also in:
kvmarm, linux-devicetree, lkml
Subsystem:
arm64 port (aarch64 architecture), kernel virtual machine for arm64 (kvm/arm64), the rest · Maintainers:
Catalin Marinas, Will Deacon, Marc Zyngier, Oliver Upton, Linus Torvalds
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 <redacted> --- 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 43af13968dfd..3eca35d5a7cf 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 <asm-generic/vmlinux.lds.h> #include <asm/cache.h> #include <asm/hyp_image.h>
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3ac0f3425833..51b53ca36dc5 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c@@ -1770,7 +1770,18 @@ 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) }
--
2.30.0.284.gd98b1dd5eaa7-goog
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