On 08/08/2025 9:23 pm, Andrew Cooper wrote:
> ... along with the supporting functions. Switch to Xen coding style, and make
> static as there are no external callers.
>
> Rename to legacy_syscall_init() as a more accurate name.
>
> No functional change.
>
> Signed-off-by: Andrew Cooper <andrew.coop...@citrix.com>
> ---
> CC: Jan Beulich <jbeul...@suse.com>
> CC: Roger Pau Monné <roger....@citrix.com>
> ---
> xen/arch/x86/include/asm/system.h | 2 -
> xen/arch/x86/traps-setup.c | 97 ++++++++++++++++++++++++++++++-
> xen/arch/x86/x86_64/traps.c | 92 -----------------------------
> 3 files changed, 95 insertions(+), 96 deletions(-)
>
> diff --git a/xen/arch/x86/include/asm/system.h
> b/xen/arch/x86/include/asm/system.h
> index 3cdc56e4ba6d..6c2800d8158d 100644
> --- a/xen/arch/x86/include/asm/system.h
> +++ b/xen/arch/x86/include/asm/system.h
> @@ -256,6 +256,4 @@ static inline int local_irq_is_enabled(void)
> #define BROKEN_ACPI_Sx 0x0001
> #define BROKEN_INIT_AFTER_S1 0x0002
>
> -void subarch_percpu_traps_init(void);
> -
> #endif
> diff --git a/xen/arch/x86/traps-setup.c b/xen/arch/x86/traps-setup.c
> index 13b8fcf0ba51..fbae7072c292 100644
> --- a/xen/arch/x86/traps-setup.c
> +++ b/xen/arch/x86/traps-setup.c
> @@ -2,13 +2,15 @@
> /*
> * Configuration of event handling for all CPUs.
> */
> +#include <xen/domain_page.h>
> #include <xen/init.h>
> #include <xen/param.h>
>
> +#include <asm/endbr.h>
> #include <asm/idt.h>
> #include <asm/msr.h>
> #include <asm/shstk.h>
> -#include <asm/system.h>
> +#include <asm/stubs.h>
> #include <asm/traps.h>
>
> DEFINE_PER_CPU_READ_MOSTLY(idt_entry_t *, idt);
> @@ -19,6 +21,8 @@ static bool __initdata opt_ler;
> boolean_param("ler", opt_ler);
>
> void nocall entry_PF(void);
> +void nocall lstar_enter(void);
> +void nocall cstar_enter(void);
>
> /*
> * Sets up system tables and descriptors for IDT devliery.
> @@ -138,6 +142,95 @@ static void load_system_tables(void)
> BUG_ON(stack_bottom & 15);
> }
>
> +static unsigned int write_stub_trampoline(
> + unsigned char *stub, unsigned long stub_va,
> + unsigned long stack_bottom, unsigned long target_va)
> +{
> + unsigned char *p = stub;
> +
> + if ( cpu_has_xen_ibt )
> + {
> + place_endbr64(p);
> + p += 4;
> + }
> +
> + /* Store guest %rax into %ss slot */
> + /* movabsq %rax, stack_bottom - 8 */
> + *p++ = 0x48;
> + *p++ = 0xa3;
> + *(uint64_t *)p = stack_bottom - 8;
> + p += 8;
> +
> + /* Store guest %rsp in %rax */
> + /* movq %rsp, %rax */
> + *p++ = 0x48;
> + *p++ = 0x89;
> + *p++ = 0xe0;
> +
> + /* Switch to Xen stack */
> + /* movabsq $stack_bottom - 8, %rsp */
> + *p++ = 0x48;
> + *p++ = 0xbc;
> + *(uint64_t *)p = stack_bottom - 8;
> + p += 8;
> +
> + /* jmp target_va */
> + *p++ = 0xe9;
> + *(int32_t *)p = target_va - (stub_va + (p - stub) + 4);
> + p += 4;
> +
> + /* Round up to a multiple of 16 bytes. */
> + return ROUNDUP(p - stub, 16);
> +}
> +
> +static void legacy_syscall_init(void)
> +{
> + unsigned long stack_bottom = get_stack_bottom();
> + unsigned long stub_va = this_cpu(stubs.addr);
> + unsigned char *stub_page;
> + unsigned int offset;
> +
> + /* No PV guests? No need to set up SYSCALL/SYSENTER infrastructure. */
> + if ( !IS_ENABLED(CONFIG_PV) )
> + return;
> +
> + stub_page = map_domain_page(_mfn(this_cpu(stubs.mfn)));
> +
> + /*
> + * Trampoline for SYSCALL entry from 64-bit mode. The VT-x HVM vcpu
> + * context switch logic relies on the SYSCALL trampoline being at the
> + * start of the stubs.
> + */
> + wrmsrl(MSR_LSTAR, stub_va);
> + offset = write_stub_trampoline(stub_page + (stub_va & ~PAGE_MASK),
> + stub_va, stack_bottom,
> + (unsigned long)lstar_enter);
> + stub_va += offset;
> +
> + if ( cpu_has_sep )
> + {
> + /* SYSENTER entry. */
> + wrmsrl(MSR_IA32_SYSENTER_ESP, stack_bottom);
> + wrmsrl(MSR_IA32_SYSENTER_EIP, (unsigned long)sysenter_entry);
> + wrmsr(MSR_IA32_SYSENTER_CS, __HYPERVISOR_CS, 0);
> + }
> +
> + /* Trampoline for SYSCALL entry from compatibility mode. */
> + wrmsrl(MSR_CSTAR, stub_va);
> + offset += write_stub_trampoline(stub_page + (stub_va & ~PAGE_MASK),
> + stub_va, stack_bottom,
> + (unsigned long)cstar_enter);
> +
> + /* Don't consume more than half of the stub space here. */
> + ASSERT(offset <= STUB_BUF_SIZE / 2);
> +
> + unmap_domain_page(stub_page);
> +
> + /* Common SYSCALL parameters. */
> + wrmsrl(MSR_STAR, XEN_MSR_STAR);
> + wrmsrl(MSR_SYSCALL_MASK, XEN_SYSCALL_MASK);
> +}
These want adjusting to use wrmsrns(), similarly to the previous patch.
Fixed locally.
~Andrew
