From: Fangyu Yu <[email protected]> riscv_kexec_relocate (copied into control_code_buffer) uses an stvec trick to drop the MMU and land on the PA of the next loop label. Under VS-mode KVM cannot emulate this single-step transition and the VCPU dies with "kvm run failed Operation not supported".
Route normal kexec through riscv_kexec_relocate_entry, the trampoline wrapper added in the previous patch. It drops SATP with PC already on a PA, then hands off to control_code_buffer where the relocate body runs with SATP=0. Drop the stvec trick from the relocate body and pass first_ind_entry as a physical address since the body now starts with SATP=0. The ".align 2" plus filler "nop" that ensured the PA of the loop top was 4-byte aligned -- required because the legacy stvec trick wrote that PA into stvec.BASE, whose low two bits are MODE and are discarded by the hardware -- is no longer load-bearing and is removed as well. Signed-off-by: Fangyu Yu <[email protected]> --- arch/riscv/kernel/kexec_relocate.S | 26 ++++++-------------------- arch/riscv/kernel/machine_kexec.c | 10 +++++++--- 2 files changed, 13 insertions(+), 23 deletions(-) diff --git a/arch/riscv/kernel/kexec_relocate.S b/arch/riscv/kernel/kexec_relocate.S index 1baadad1b546..29392f457f42 100644 --- a/arch/riscv/kernel/kexec_relocate.S +++ b/arch/riscv/kernel/kexec_relocate.S @@ -34,27 +34,13 @@ SYM_CODE_START(riscv_kexec_relocate) csrw CSR_SIP, zero /* - * When we switch SATP.MODE to "Bare" we'll only - * play with physical addresses. However the first time - * we try to jump somewhere, the offset on the jump - * will be relative to pc which will still be on VA. To - * deal with this we set stvec to the physical address at - * the start of the loop below so that we jump there in - * any case. + * The trampoline wrapper (riscv_kexec_relocate_entry) has already + * dropped the MMU and handed control to us at this PA copy of the + * relocate code. From here on the entire loop runs with SATP=0 and + * every address (s0, s5, source/dest pointers) is a physical one. */ - la s6, 1f - sub s6, s6, s4 - csrw CSR_STVEC, s6 - - /* - * With C-extension, here we get 42 Bytes and the next - * .align directive would pad zeros here up to 44 Bytes. - * So manually put a nop here to avoid zeros padding. - */ - nop /* Process entries in a loop */ -.align 2 1: REG_L t0, 0(s0) /* t0 = *image->entry */ addi s0, s0, RISCV_SZPTR /* image->entry++ */ @@ -70,8 +56,8 @@ SYM_CODE_START(riscv_kexec_relocate) andi t1, t0, 0x2 beqz t1, 2f andi s0, t0, ~0x2 - csrw CSR_SATP, zero - jr s6 + /* MMU is already off; the entry wrapper handled the transition. */ + j 1b 2: /* IND_DONE entry ? -> jump to done label */ diff --git a/arch/riscv/kernel/machine_kexec.c b/arch/riscv/kernel/machine_kexec.c index e3eb1e71920a..99cc251f971c 100644 --- a/arch/riscv/kernel/machine_kexec.c +++ b/arch/riscv/kernel/machine_kexec.c @@ -231,11 +231,15 @@ machine_kexec(struct kimage *image) { struct kimage_arch *internal = &image->arch; unsigned long jump_addr = (unsigned long) image->start; - unsigned long first_ind_entry = (unsigned long) &image->head; + /* + * The relocate body runs entirely with the MMU off (the wrapper + * drops SATP before jumping into control_code_buffer), so the very + * first entry must be a physical address. + */ + unsigned long first_ind_entry = __pa(&image->head); unsigned long this_cpu_id = __smp_processor_id(); unsigned long this_hart_id = cpuid_to_hartid_map(this_cpu_id); unsigned long fdt_addr = internal->fdt_addr; - void *control_code_buffer = page_address(image->control_code_page); riscv_kexec_method kexec_method = NULL; #ifdef CONFIG_SMP @@ -244,7 +248,7 @@ machine_kexec(struct kimage *image) #endif if (image->type != KEXEC_TYPE_CRASH) - kexec_method = control_code_buffer; + kexec_method = (riscv_kexec_method) &riscv_kexec_relocate_entry; else kexec_method = (riscv_kexec_method) &riscv_kexec_norelocate; -- 2.50.1
