| Message ID | 20210108121524.656872-8-qperret@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM/arm64: A stage 2 for the host | expand |
On Fri, Jan 08, 2021 at 12:15:05PM +0000, Quentin Perret wrote: > 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 <qperret@google.com> > --- > 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) \ Use HYP_SECTION_NAME() here? > + . = ALIGN(PAGE_SIZE); \ > + __hyp_bss_end = .; Should this be gated on CONFIG_KVM like the other hyp sections are? In fact, it might be nice to define all of those together. Yeah, it means moving things higher up in the file, but I think it will be easier to read. > #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), I think it would be clearer to refer to __hyp_bss_start here ^^. You could always add an ASSERT in the linker script if you want to catch anybody adding something before the hyp bss in future. Will
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) }
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 <qperret@google.com> --- 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(+)