| Message ID | 03ef20c327c6f4a0ce47078dae52465b3cb32d2e.1692744718.git.sanastasio@raptorengineering.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/ppc: Add early Radix MMU support | expand |
On 23.08.2023 01:03, Shawn Anastasio wrote: > Introduce a small assembly loop in `start` to copy the kernel to > physical address 0 before continuing. This ensures that the physical > address lines up with XEN_VIRT_START (0xc000000000000000) and allows us > to identity map the kernel when the MMU is set up in the next patch. > > We are also able to start execution at XEN_VIRT_START after the copy > since hardware will ignore the top 4 address bits when operating in Real > Mode (MMU off). > > Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com> Reviewed-by: Jan Beulich <jbeulich@suse.com>
diff --git a/xen/arch/ppc/include/asm/config.h b/xen/arch/ppc/include/asm/config.h index d060f0dca7..30438d22d2 100644 --- a/xen/arch/ppc/include/asm/config.h +++ b/xen/arch/ppc/include/asm/config.h @@ -39,7 +39,7 @@ name: #endif -#define XEN_VIRT_START _AT(UL, 0xc000000000000000) +#define XEN_VIRT_START _AC(0xc000000000000000, UL) #define SMP_CACHE_BYTES (1 << 6) diff --git a/xen/arch/ppc/ppc64/head.S b/xen/arch/ppc/ppc64/head.S index 8f1e5d3ad2..a149339ad0 100644 --- a/xen/arch/ppc/ppc64/head.S +++ b/xen/arch/ppc/ppc64/head.S @@ -17,6 +17,33 @@ ENTRY(start) addis %r2, %r12, .TOC.-1b@ha addi %r2, %r2, .TOC.-1b@l + /* + * Copy Xen to physical address zero and jump to XEN_VIRT_START + * (0xc000000000000000). This works because the hardware will ignore the top + * four address bits when the MMU is off. + */ + LOAD_REG_ADDR(%r14, _start) + LOAD_IMM64(%r12, XEN_VIRT_START) + + /* If we're at the correct address, skip copy */ + cmpld %r14, %r12 + beq .L_correct_address + + /* Copy bytes until _end */ + LOAD_REG_ADDR(%r11, _end) + addi %r14, %r14, -8 + li %r13, -8 +.L_copy_xen: + ldu %r10, 8(%r14) + stdu %r10, 8(%r13) + cmpld %r14, %r11 + blt .L_copy_xen + + /* Jump to XEN_VIRT_START */ + mtctr %r12 + bctr +.L_correct_address: + /* set up the initial stack */ LOAD_REG_ADDR(%r1, cpu0_boot_stack) li %r11, 0
Introduce a small assembly loop in `start` to copy the kernel to physical address 0 before continuing. This ensures that the physical address lines up with XEN_VIRT_START (0xc000000000000000) and allows us to identity map the kernel when the MMU is set up in the next patch. We are also able to start execution at XEN_VIRT_START after the copy since hardware will ignore the top 4 address bits when operating in Real Mode (MMU off). Signed-off-by: Shawn Anastasio <sanastasio@raptorengineering.com> --- v4: - Don't re-use stack pointer register (%r1) for non-stack-related purposes in head.S v3: no changes. v2: - Fix definition of XEN_VIRT_START macro which incorrectly used _AT instead of _AC. - Use _start instead of start as symbol referring to beginning of Xen binary xen/arch/ppc/include/asm/config.h | 2 +- xen/arch/ppc/ppc64/head.S | 27 +++++++++++++++++++++++++++ 2 files changed, 28 insertions(+), 1 deletion(-) -- 2.30.2