| Message ID | 20210916231325.125533-9-pasha.tatashin@soleen.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | arm64: MMU enabled kexec relocation | expand |
On Thu, Sep 16, 2021 at 07:13:18PM -0400, Pasha Tatashin wrote: > If we have a EL2 mode without VHE, the EL2 vectors are needed in order > to switch to EL2 and jump to new world with hypervisor privileges. > > In preparation to MMU enabled relocation, configure our EL2 table now. > > Kexec uses #HVC_SOFT_RESTART to branch to the new world, so extend > el1_sync vector that is provided by trans_pgd_copy_el2_vectors() to > support this case. > > Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> > --- > arch/arm64/Kconfig | 2 +- > arch/arm64/include/asm/kexec.h | 1 + > arch/arm64/kernel/asm-offsets.c | 1 + > arch/arm64/kernel/machine_kexec.c | 31 +++++++++++++++++++++++++++++++ > arch/arm64/mm/trans_pgd-asm.S | 9 ++++++++- > 5 files changed, 42 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 5c7ae4c3954b..552a057b40af 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -1135,7 +1135,7 @@ config CRASH_DUMP > > config TRANS_TABLE > def_bool y > - depends on HIBERNATION > + depends on HIBERNATION || KEXEC_CORE > > config XEN_DOM0 > def_bool y > diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h > index 00dbcc71aeb2..753a1c398898 100644 > --- a/arch/arm64/include/asm/kexec.h > +++ b/arch/arm64/include/asm/kexec.h > @@ -96,6 +96,7 @@ struct kimage_arch { > void *dtb; > phys_addr_t dtb_mem; > phys_addr_t kern_reloc; > + phys_addr_t el2_vectors; > }; > > #ifdef CONFIG_KEXEC_FILE > diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c > index 1d3319c7518e..6a2b8b1a4872 100644 > --- a/arch/arm64/kernel/asm-offsets.c > +++ b/arch/arm64/kernel/asm-offsets.c > @@ -174,6 +174,7 @@ int main(void) > #endif > #ifdef CONFIG_KEXEC_CORE > DEFINE(KIMAGE_ARCH_DTB_MEM, offsetof(struct kimage, arch.dtb_mem)); > + DEFINE(KIMAGE_ARCH_EL2_VECTORS, offsetof(struct kimage, arch.el2_vectors)); > DEFINE(KIMAGE_HEAD, offsetof(struct kimage, head)); > DEFINE(KIMAGE_START, offsetof(struct kimage, start)); > BLANK(); > diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c > index e210b19592c6..59a4b4172b68 100644 > --- a/arch/arm64/kernel/machine_kexec.c > +++ b/arch/arm64/kernel/machine_kexec.c > @@ -21,6 +21,7 @@ > #include <asm/mmu.h> > #include <asm/mmu_context.h> > #include <asm/page.h> > +#include <asm/trans_pgd.h> > > #include "cpu-reset.h" > > @@ -43,7 +44,9 @@ static void _kexec_image_info(const char *func, int line, > pr_debug(" start: %lx\n", kimage->start); > pr_debug(" head: %lx\n", kimage->head); > pr_debug(" nr_segments: %lu\n", kimage->nr_segments); > + pr_debug(" dtb_mem: %pa\n", &kimage->arch.dtb_mem); > pr_debug(" kern_reloc: %pa\n", &kimage->arch.kern_reloc); > + pr_debug(" el2_vectors: %pa\n", &kimage->arch.el2_vectors); > > for (i = 0; i < kimage->nr_segments; i++) { > pr_debug(" segment[%lu]: %016lx - %016lx, 0x%lx bytes, %lu pages\n", > @@ -143,9 +146,27 @@ static void kexec_segment_flush(const struct kimage *kimage) > } > } > > +/* Allocates pages for kexec page table */ > +static void *kexec_page_alloc(void *arg) > +{ > + struct kimage *kimage = (struct kimage *)arg; > + struct page *page = kimage_alloc_control_pages(kimage, 0); > + > + if (!page) > + return NULL; > + > + memset(page_address(page), 0, PAGE_SIZE); Hmm, I think we might be missing barriers here to ensure that the zeroes are visible to the page-table walker before we plumb the page into the page-table. Usually, that's taken care of by the smp_wmb() in __pXX_alloc() but I can't see that here. Is it hiding? Will
> > +/* Allocates pages for kexec page table */ > > +static void *kexec_page_alloc(void *arg) > > +{ > > + struct kimage *kimage = (struct kimage *)arg; > > + struct page *page = kimage_alloc_control_pages(kimage, 0); > > + > > + if (!page) > > + return NULL; > > + > > + memset(page_address(page), 0, PAGE_SIZE); > > Hmm, I think we might be missing barriers here to ensure that the zeroes > are visible to the page-table walker before we plumb the page into the > page-table. > > Usually, that's taken care of by the smp_wmb() in __pXX_alloc() but I > can't see that here. Is it hiding? Based on the comment in __pte_alloc() that smp_wmb() is needed in order to synchronize pte setup with other cpus prior to making it visible to them. This is not needed here. First, by the time these page tables are used the other cpus are offlined (kexec reboot code is single threaded). Second, we never insert any entry into a page table that is actively used by any cpu. Pasha
On Wed, Sep 29, 2021 at 11:54:55PM -0400, Pasha Tatashin wrote: > > > +/* Allocates pages for kexec page table */ > > > +static void *kexec_page_alloc(void *arg) > > > +{ > > > + struct kimage *kimage = (struct kimage *)arg; > > > + struct page *page = kimage_alloc_control_pages(kimage, 0); > > > + > > > + if (!page) > > > + return NULL; > > > + > > > + memset(page_address(page), 0, PAGE_SIZE); > > > > Hmm, I think we might be missing barriers here to ensure that the zeroes > > are visible to the page-table walker before we plumb the page into the > > page-table. > > > > Usually, that's taken care of by the smp_wmb() in __pXX_alloc() but I > > can't see that here. Is it hiding? > > Based on the comment in __pte_alloc() that smp_wmb() is needed in > order to synchronize pte setup with other cpus prior to making it > visible to them. This is not needed here. First, by the time these > page tables are used the other cpus are offlined (kexec reboot code is > single threaded). Second, we never insert any entry into a page table > that is actively used by any cpu. I think the comment there is wrong, but the barrier is still necessary. How else do you guarantee that the page-table walker reads the zeroes from the memset? Will
On Thu, Sep 30, 2021 at 4:16 AM Will Deacon <will@kernel.org> wrote: > > On Wed, Sep 29, 2021 at 11:54:55PM -0400, Pasha Tatashin wrote: > > > > +/* Allocates pages for kexec page table */ > > > > +static void *kexec_page_alloc(void *arg) > > > > +{ > > > > + struct kimage *kimage = (struct kimage *)arg; > > > > + struct page *page = kimage_alloc_control_pages(kimage, 0); > > > > + > > > > + if (!page) > > > > + return NULL; > > > > + > > > > + memset(page_address(page), 0, PAGE_SIZE); > > > > > > Hmm, I think we might be missing barriers here to ensure that the zeroes > > > are visible to the page-table walker before we plumb the page into the > > > page-table. > > > > > > Usually, that's taken care of by the smp_wmb() in __pXX_alloc() but I > > > can't see that here. Is it hiding? > > > > Based on the comment in __pte_alloc() that smp_wmb() is needed in > > order to synchronize pte setup with other cpus prior to making it > > visible to them. This is not needed here. First, by the time these > > page tables are used the other cpus are offlined (kexec reboot code is > > single threaded). Second, we never insert any entry into a page table > > that is actively used by any cpu. > > I think the comment there is wrong, but the barrier is still necessary. > How else do you guarantee that the page-table walker reads the zeroes from > the memset? True, good point. We are still safe because we have the following: cpu_install_ttbr0() is used to load trans_pgd tables both in kexec and hibernate cases. cpu_install_ttbr0 has: local_flush_tlb_all() dsb(nshst); // Ensure prior page-table updates have completed __tlbi(vmalle1); // Invalidate the TLB dsb(nsh); // Ensure the TLB invalidation has completed isb(); // Discard any instructions fetched from the old mapping Pasha
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 5c7ae4c3954b..552a057b40af 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1135,7 +1135,7 @@ config CRASH_DUMP config TRANS_TABLE def_bool y - depends on HIBERNATION + depends on HIBERNATION || KEXEC_CORE config XEN_DOM0 def_bool y diff --git a/arch/arm64/include/asm/kexec.h b/arch/arm64/include/asm/kexec.h index 00dbcc71aeb2..753a1c398898 100644 --- a/arch/arm64/include/asm/kexec.h +++ b/arch/arm64/include/asm/kexec.h @@ -96,6 +96,7 @@ struct kimage_arch { void *dtb; phys_addr_t dtb_mem; phys_addr_t kern_reloc; + phys_addr_t el2_vectors; }; #ifdef CONFIG_KEXEC_FILE diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c index 1d3319c7518e..6a2b8b1a4872 100644 --- a/arch/arm64/kernel/asm-offsets.c +++ b/arch/arm64/kernel/asm-offsets.c @@ -174,6 +174,7 @@ int main(void) #endif #ifdef CONFIG_KEXEC_CORE DEFINE(KIMAGE_ARCH_DTB_MEM, offsetof(struct kimage, arch.dtb_mem)); + DEFINE(KIMAGE_ARCH_EL2_VECTORS, offsetof(struct kimage, arch.el2_vectors)); DEFINE(KIMAGE_HEAD, offsetof(struct kimage, head)); DEFINE(KIMAGE_START, offsetof(struct kimage, start)); BLANK(); diff --git a/arch/arm64/kernel/machine_kexec.c b/arch/arm64/kernel/machine_kexec.c index e210b19592c6..59a4b4172b68 100644 --- a/arch/arm64/kernel/machine_kexec.c +++ b/arch/arm64/kernel/machine_kexec.c @@ -21,6 +21,7 @@ #include <asm/mmu.h> #include <asm/mmu_context.h> #include <asm/page.h> +#include <asm/trans_pgd.h> #include "cpu-reset.h" @@ -43,7 +44,9 @@ static void _kexec_image_info(const char *func, int line, pr_debug(" start: %lx\n", kimage->start); pr_debug(" head: %lx\n", kimage->head); pr_debug(" nr_segments: %lu\n", kimage->nr_segments); + pr_debug(" dtb_mem: %pa\n", &kimage->arch.dtb_mem); pr_debug(" kern_reloc: %pa\n", &kimage->arch.kern_reloc); + pr_debug(" el2_vectors: %pa\n", &kimage->arch.el2_vectors); for (i = 0; i < kimage->nr_segments; i++) { pr_debug(" segment[%lu]: %016lx - %016lx, 0x%lx bytes, %lu pages\n", @@ -143,9 +146,27 @@ static void kexec_segment_flush(const struct kimage *kimage) } } +/* Allocates pages for kexec page table */ +static void *kexec_page_alloc(void *arg) +{ + struct kimage *kimage = (struct kimage *)arg; + struct page *page = kimage_alloc_control_pages(kimage, 0); + + if (!page) + return NULL; + + memset(page_address(page), 0, PAGE_SIZE); + + return page_address(page); +} + int machine_kexec_post_load(struct kimage *kimage) { void *reloc_code = page_to_virt(kimage->control_code_page); + struct trans_pgd_info info = { + .trans_alloc_page = kexec_page_alloc, + .trans_alloc_arg = kimage, + }; /* If in place, relocation is not used, only flush next kernel */ if (kimage->head & IND_DONE) { @@ -154,6 +175,14 @@ int machine_kexec_post_load(struct kimage *kimage) return 0; } + kimage->arch.el2_vectors = 0; + if (is_hyp_nvhe()) { + int rc = trans_pgd_copy_el2_vectors(&info, + &kimage->arch.el2_vectors); + if (rc) + return rc; + } + memcpy(reloc_code, arm64_relocate_new_kernel, arm64_relocate_new_kernel_size); kimage->arch.kern_reloc = __pa(reloc_code); @@ -209,6 +238,8 @@ void machine_kexec(struct kimage *kimage) restart(is_hyp_nvhe(), kimage->start, kimage->arch.dtb_mem, 0, 0); } else { + if (is_hyp_nvhe()) + __hyp_set_vectors(kimage->arch.el2_vectors); cpu_soft_restart(kimage->arch.kern_reloc, virt_to_phys(kimage), 0, 0); } diff --git a/arch/arm64/mm/trans_pgd-asm.S b/arch/arm64/mm/trans_pgd-asm.S index 8c4bffe3089d..021c31573bcb 100644 --- a/arch/arm64/mm/trans_pgd-asm.S +++ b/arch/arm64/mm/trans_pgd-asm.S @@ -24,7 +24,14 @@ SYM_CODE_START_LOCAL(el1_sync) msr vbar_el2, x1 mov x0, xzr eret -1: /* Unexpected argument, set an error */ +1: cmp x0, #HVC_SOFT_RESTART /* Called from kexec */ + b.ne 2f + mov x0, x2 + mov x2, x4 + mov x4, x1 + mov x1, x3 + br x4 +2: /* Unexpected argument, set an error */ mov_q x0, HVC_STUB_ERR eret SYM_CODE_END(el1_sync)
If we have a EL2 mode without VHE, the EL2 vectors are needed in order to switch to EL2 and jump to new world with hypervisor privileges. In preparation to MMU enabled relocation, configure our EL2 table now. Kexec uses #HVC_SOFT_RESTART to branch to the new world, so extend el1_sync vector that is provided by trans_pgd_copy_el2_vectors() to support this case. Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com> --- arch/arm64/Kconfig | 2 +- arch/arm64/include/asm/kexec.h | 1 + arch/arm64/kernel/asm-offsets.c | 1 + arch/arm64/kernel/machine_kexec.c | 31 +++++++++++++++++++++++++++++++ arch/arm64/mm/trans_pgd-asm.S | 9 ++++++++- 5 files changed, 42 insertions(+), 2 deletions(-)