Re: [Xen-devel] [PATCH 1/2] x86: init_hypercall_page() cleanup

["Woods, Brian" <Brian.Woods@amd.com>]

On Thu, May 23, 2019 at 11:20:15AM +0100, Andy Cooper wrote:
> [CAUTION: External Email]
> 
> The various pieces of the hypercall page infrastructure have grown
> organically over time and ended up in a bit of a mess.
> 
>  * Rename all functions to be of the form *_init_hypercall_page().  This
>    makes them somewhat shorter, and means they can actually be grepped
>    for in one go.
>  * Move init_hypercall_page() to domain.c.  The 64-bit traps.c isn't a
>    terribly appropriate place for it to live.
>  * Drop an obsolete comment from hvm_init_hypercall_page() and drop the
>    domain parameter from hvm_funcs.init_hypercall_page() as it isn't
>    necessary.
>  * Rearrange the logic in the each function to avoid needing extra local
>    variables, and to write the page in one single pass.
> 
> No functional change.
> 
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

Acked-by: Brian Woods <brian.woods@amd.com>

> ---
> CC: Jan Beulich <JBeulich@suse.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> CC: Roger Pau Monné <roger.pau@citrix.com>
> CC: Jun Nakajima <jun.nakajima@intel.com>
> CC: Kevin Tian <kevin.tian@intel.com>
> CC: Boris Ostrovsky <boris.ostrovsky@oracle.com>
> CC: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
> CC: Brian Woods <brian.woods@amd.com>
> ---
>  xen/arch/x86/domain.c           | 14 +++++++++
>  xen/arch/x86/domctl.c           |  2 +-
>  xen/arch/x86/hvm/hvm.c          |  8 ++----
>  xen/arch/x86/hvm/svm/svm.c      | 18 ++++++------
>  xen/arch/x86/hvm/vmx/vmx.c      | 18 ++++++------
>  xen/arch/x86/pv/dom0_build.c    |  3 +-
>  xen/arch/x86/pv/hypercall.c     | 63 ++++++++++++++++++++---------------------
>  xen/arch/x86/traps.c            |  2 +-
>  xen/arch/x86/x86_64/traps.c     | 13 ---------
>  xen/include/asm-x86/domain.h    |  2 +-
>  xen/include/asm-x86/hvm/hvm.h   |  4 +--
>  xen/include/asm-x86/hypercall.h |  4 +--
>  12 files changed, 73 insertions(+), 78 deletions(-)
> 
> diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
> index ac960dd..9485a17 100644
> --- a/xen/arch/x86/domain.c
> +++ b/xen/arch/x86/domain.c
> @@ -175,6 +175,20 @@ static void noreturn continue_idle_domain(struct vcpu *v)
>      reset_stack_and_jump(idle_loop);
>  }
> 
> +void init_hypercall_page(struct domain *d, void *ptr)
> +{
> +    memset(ptr, 0xcc, PAGE_SIZE);
> +
> +    if ( is_hvm_domain(d) )
> +        hvm_init_hypercall_page(d, ptr);
> +    else if ( is_pv_64bit_domain(d) )
> +        pv_ring3_init_hypercall_page(ptr);
> +    else if ( is_pv_32bit_domain(d) )
> +        pv_ring1_init_hypercall_page(ptr);
> +    else
> +        ASSERT_UNREACHABLE();
> +}
> +
>  void dump_pageframe_info(struct domain *d)
>  {
>      struct page_info *page;
> diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> index 9bf2d08..7c6b809 100644
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -517,7 +517,7 @@ long arch_do_domctl(
>          }
> 
>          hypercall_page = __map_domain_page(page);
> -        hypercall_page_initialise(d, hypercall_page);
> +        init_hypercall_page(d, hypercall_page);
>          unmap_domain_page(hypercall_page);
> 
>          put_page_and_type(page);
> diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
> index 8993c2a..5666286 100644
> --- a/xen/arch/x86/hvm/hvm.c
> +++ b/xen/arch/x86/hvm/hvm.c
> @@ -3801,13 +3801,11 @@ static void hvm_latch_shinfo_size(struct domain *d)
>      }
>  }
> 
> -/* Initialise a hypercall transfer page for a VMX domain using
> -   paravirtualised drivers. */
> -void hvm_hypercall_page_initialise(struct domain *d,
> -                                   void *hypercall_page)
> +void hvm_init_hypercall_page(struct domain *d, void *ptr)
>  {
>      hvm_latch_shinfo_size(d);
> -    alternative_vcall(hvm_funcs.init_hypercall_page, d, hypercall_page);
> +
> +    alternative_vcall(hvm_funcs.init_hypercall_page, ptr);
>  }
> 
>  void hvm_vcpu_reset_state(struct vcpu *v, uint16_t cs, uint16_t ip)
> diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
> index 9f26493..cd6a6b3 100644
> --- a/xen/arch/x86/hvm/svm/svm.c
> +++ b/xen/arch/x86/hvm/svm/svm.c
> @@ -916,17 +916,20 @@ static unsigned int svm_get_insn_bytes(struct vcpu *v, uint8_t *buf)
>      return len;
>  }
> 
> -static void svm_init_hypercall_page(struct domain *d, void *hypercall_page)
> +static void svm_init_hypercall_page(void *p)
>  {
> -    char *p;
> -    int i;
> +    unsigned int i;
> 
> -    for ( i = 0; i < (PAGE_SIZE / 32); i++ )
> +    for ( i = 0; i < (PAGE_SIZE / 32); i++, p += 32 )
>      {
> -        if ( i == __HYPERVISOR_iret )
> +        if ( unlikely(i == __HYPERVISOR_iret) )
> +        {
> +            /* HYPERVISOR_iret isn't supported */
> +            *(u16 *)p = 0x0b0f; /* ud2 */
> +
>              continue;
> +        }
> 
> -        p = (char *)(hypercall_page + (i * 32));
>          *(u8  *)(p + 0) = 0xb8; /* mov imm32, %eax */
>          *(u32 *)(p + 1) = i;
>          *(u8  *)(p + 5) = 0x0f; /* vmmcall */
> @@ -934,9 +937,6 @@ static void svm_init_hypercall_page(struct domain *d, void *hypercall_page)
>          *(u8  *)(p + 7) = 0xd9;
>          *(u8  *)(p + 8) = 0xc3; /* ret */
>      }
> -
> -    /* Don't support HYPERVISOR_iret at the moment */
> -    *(u16 *)(hypercall_page + (__HYPERVISOR_iret * 32)) = 0x0b0f; /* ud2 */
>  }
> 
>  static inline void svm_tsc_ratio_save(struct vcpu *v)
> diff --git a/xen/arch/x86/hvm/vmx/vmx.c b/xen/arch/x86/hvm/vmx/vmx.c
> index 7d96678..0060310 100644
> --- a/xen/arch/x86/hvm/vmx/vmx.c
> +++ b/xen/arch/x86/hvm/vmx/vmx.c
> @@ -1262,17 +1262,20 @@ static void vmx_set_descriptor_access_exiting(struct vcpu *v, bool enable)
>      vmx_vmcs_exit(v);
>  }
> 
> -static void vmx_init_hypercall_page(struct domain *d, void *hypercall_page)
> +static void vmx_init_hypercall_page(void *p)
>  {
> -    char *p;
> -    int i;
> +    unsigned int i;
> 
> -    for ( i = 0; i < (PAGE_SIZE / 32); i++ )
> +    for ( i = 0; i < (PAGE_SIZE / 32); i++, p += 32 )
>      {
> -        if ( i == __HYPERVISOR_iret )
> +        if ( unlikely(i == __HYPERVISOR_iret) )
> +        {
> +            /* HYPERVISOR_iret isn't supported */
> +            *(u16 *)p = 0x0b0f; /* ud2 */
> +
>              continue;
> +        }
> 
> -        p = (char *)(hypercall_page + (i * 32));
>          *(u8  *)(p + 0) = 0xb8; /* mov imm32, %eax */
>          *(u32 *)(p + 1) = i;
>          *(u8  *)(p + 5) = 0x0f; /* vmcall */
> @@ -1280,9 +1283,6 @@ static void vmx_init_hypercall_page(struct domain *d, void *hypercall_page)
>          *(u8  *)(p + 7) = 0xc1;
>          *(u8  *)(p + 8) = 0xc3; /* ret */
>      }
> -
> -    /* Don't support HYPERVISOR_iret at the moment */
> -    *(u16 *)(hypercall_page + (__HYPERVISOR_iret * 32)) = 0x0b0f; /* ud2 */
>  }
> 
>  static unsigned int vmx_get_interrupt_shadow(struct vcpu *v)
> diff --git a/xen/arch/x86/pv/dom0_build.c b/xen/arch/x86/pv/dom0_build.c
> index cef2d42..d48d014 100644
> --- a/xen/arch/x86/pv/dom0_build.c
> +++ b/xen/arch/x86/pv/dom0_build.c
> @@ -738,8 +738,7 @@ int __init dom0_construct_pv(struct domain *d,
>              rc = -1;
>              goto out;
>          }
> -        hypercall_page_initialise(
> -            d, (void *)(unsigned long)parms.virt_hypercall);
> +        init_hypercall_page(d, _p(parms.virt_hypercall));
>      }
> 
>      /* Free temporary buffers. */
> diff --git a/xen/arch/x86/pv/hypercall.c b/xen/arch/x86/pv/hypercall.c
> index 5fdb8f9..0c84c0b 100644
> --- a/xen/arch/x86/pv/hypercall.c
> +++ b/xen/arch/x86/pv/hypercall.c
> @@ -267,16 +267,28 @@ enum mc_disposition arch_do_multicall_call(struct mc_state *state)
>               ? mc_continue : mc_preempt;
>  }
> 
> -void hypercall_page_initialise_ring3_kernel(void *hypercall_page)
> +void pv_ring3_init_hypercall_page(void *p)
>  {
> -    void *p = hypercall_page;
>      unsigned int i;
> 
> -    /* Fill in all the transfer points with template machine code. */
>      for ( i = 0; i < (PAGE_SIZE / 32); i++, p += 32 )
>      {
> -        if ( i == __HYPERVISOR_iret )
> +        if ( unlikely(i == __HYPERVISOR_iret) )
> +        {
> +            /*
> +             * HYPERVISOR_iret is special because it doesn't return and
> +             * expects a special stack frame. Guests jump at this transfer
> +             * point instead of calling it.
> +             */
> +            *(u8  *)(p+ 0) = 0x51;    /* push %rcx */
> +            *(u16 *)(p+ 1) = 0x5341;  /* push %r11 */
> +            *(u8  *)(p+ 3) = 0x50;    /* push %rax */
> +            *(u8  *)(p+ 4) = 0xb8;    /* mov  $__HYPERVISOR_iret, %eax */
> +            *(u32 *)(p+ 5) = __HYPERVISOR_iret;
> +            *(u16 *)(p+ 9) = 0x050f;  /* syscall */
> +
>              continue;
> +        }
> 
>          *(u8  *)(p+ 0) = 0x51;    /* push %rcx */
>          *(u16 *)(p+ 1) = 0x5341;  /* push %r11 */
> @@ -287,49 +299,34 @@ void hypercall_page_initialise_ring3_kernel(void *hypercall_page)
>          *(u8  *)(p+12) = 0x59;    /* pop  %rcx */
>          *(u8  *)(p+13) = 0xc3;    /* ret */
>      }
> -
> -    /*
> -     * HYPERVISOR_iret is special because it doesn't return and expects a
> -     * special stack frame. Guests jump at this transfer point instead of
> -     * calling it.
> -     */
> -    p = hypercall_page + (__HYPERVISOR_iret * 32);
> -    *(u8  *)(p+ 0) = 0x51;    /* push %rcx */
> -    *(u16 *)(p+ 1) = 0x5341;  /* push %r11 */
> -    *(u8  *)(p+ 3) = 0x50;    /* push %rax */
> -    *(u8  *)(p+ 4) = 0xb8;    /* mov  $__HYPERVISOR_iret,%eax */
> -    *(u32 *)(p+ 5) = __HYPERVISOR_iret;
> -    *(u16 *)(p+ 9) = 0x050f;  /* syscall */
>  }
> 
> -void hypercall_page_initialise_ring1_kernel(void *hypercall_page)
> +void pv_ring1_init_hypercall_page(void *p)
>  {
> -    void *p = hypercall_page;
>      unsigned int i;
> 
> -    /* Fill in all the transfer points with template machine code. */
> -
>      for ( i = 0; i < (PAGE_SIZE / 32); i++, p += 32 )
>      {
> -        if ( i == __HYPERVISOR_iret )
> +        if ( unlikely(i == __HYPERVISOR_iret) )
> +        {
> +            /*
> +             * HYPERVISOR_iret is special because it doesn't return and
> +             * expects a special stack frame. Guests jump at this transfer
> +             * point instead of calling it.
> +             */
> +            *(u8  *)(p+ 0) = 0x50;    /* push %eax */
> +            *(u8  *)(p+ 1) = 0xb8;    /* mov  $__HYPERVISOR_iret, %eax */
> +            *(u32 *)(p+ 2) = __HYPERVISOR_iret;
> +            *(u16 *)(p+ 6) = (HYPERCALL_VECTOR << 8) | 0xcd; /* int  $xx */
> +
>              continue;
> +        }
> 
>          *(u8  *)(p+ 0) = 0xb8;    /* mov  $<i>,%eax */
>          *(u32 *)(p+ 1) = i;
>          *(u16 *)(p+ 5) = (HYPERCALL_VECTOR << 8) | 0xcd; /* int  $xx */
>          *(u8  *)(p+ 7) = 0xc3;    /* ret */
>      }
> -
> -    /*
> -     * HYPERVISOR_iret is special because it doesn't return and expects a
> -     * special stack frame. Guests jump at this transfer point instead of
> -     * calling it.
> -     */
> -    p = hypercall_page + (__HYPERVISOR_iret * 32);
> -    *(u8  *)(p+ 0) = 0x50;    /* push %eax */
> -    *(u8  *)(p+ 1) = 0xb8;    /* mov  $__HYPERVISOR_iret,%eax */
> -    *(u32 *)(p+ 2) = __HYPERVISOR_iret;
> -    *(u16 *)(p+ 6) = (HYPERCALL_VECTOR << 8) | 0xcd; /* int  $xx */
>  }
> 
>  /*
> diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
> index 05ddc39..ba1053f 100644
> --- a/xen/arch/x86/traps.c
> +++ b/xen/arch/x86/traps.c
> @@ -828,7 +828,7 @@ int guest_wrmsr_xen(struct vcpu *v, uint32_t idx, uint64_t val)
>          }
> 
>          hypercall_page = __map_domain_page(page);
> -        hypercall_page_initialise(d, hypercall_page);
> +        init_hypercall_page(d, hypercall_page);
>          unmap_domain_page(hypercall_page);
> 
>          put_page_and_type(page);
> diff --git a/xen/arch/x86/x86_64/traps.c b/xen/arch/x86/x86_64/traps.c
> index cb4bf0a..23d9357 100644
> --- a/xen/arch/x86/x86_64/traps.c
> +++ b/xen/arch/x86/x86_64/traps.c
> @@ -360,19 +360,6 @@ void subarch_percpu_traps_init(void)
>      wrmsrl(MSR_SYSCALL_MASK, XEN_SYSCALL_MASK);
>  }
> 
> -void hypercall_page_initialise(struct domain *d, void *hypercall_page)
> -{
> -    memset(hypercall_page, 0xCC, PAGE_SIZE);
> -    if ( is_hvm_domain(d) )
> -        hvm_hypercall_page_initialise(d, hypercall_page);
> -    else if ( is_pv_64bit_domain(d) )
> -        hypercall_page_initialise_ring3_kernel(hypercall_page);
> -    else if ( is_pv_32bit_domain(d) )
> -        hypercall_page_initialise_ring1_kernel(hypercall_page);
> -    else
> -        ASSERT_UNREACHABLE();
> -}
> -
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/xen/include/asm-x86/domain.h b/xen/include/asm-x86/domain.h
> index 214e44c..72dea80 100644
> --- a/xen/include/asm-x86/domain.h
> +++ b/xen/include/asm-x86/domain.h
> @@ -83,7 +83,7 @@ void cpuid_policy_updated(struct vcpu *v);
>   * Initialise a hypercall-transfer page. The given pointer must be mapped
>   * in Xen virtual address space (accesses are not validated or checked).
>   */
> -void hypercall_page_initialise(struct domain *d, void *);
> +void init_hypercall_page(struct domain *d, void *);
> 
>  /************************************************/
>  /*          shadow paging extension             */
> diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
> index 1921422..b327bd2 100644
> --- a/xen/include/asm-x86/hvm/hvm.h
> +++ b/xen/include/asm-x86/hvm/hvm.h
> @@ -152,7 +152,7 @@ struct hvm_function_table {
> 
>      void (*inject_event)(const struct x86_event *event);
> 
> -    void (*init_hypercall_page)(struct domain *d, void *hypercall_page);
> +    void (*init_hypercall_page)(void *ptr);
> 
>      bool (*event_pending)(const struct vcpu *v);
>      bool (*get_pending_event)(struct vcpu *v, struct x86_event *info);
> @@ -272,7 +272,7 @@ int hvm_girq_dest_2_vcpu_id(struct domain *d, uint8_t dest, uint8_t dest_mode);
>  enum hvm_intblk
>  hvm_interrupt_blocked(struct vcpu *v, struct hvm_intack intack);
> 
> -void hvm_hypercall_page_initialise(struct domain *d, void *hypercall_page);
> +void hvm_init_hypercall_page(struct domain *d, void *ptr);
> 
>  void hvm_get_segment_register(struct vcpu *v, enum x86_segment seg,
>                                struct segment_register *reg);
> diff --git a/xen/include/asm-x86/hypercall.h b/xen/include/asm-x86/hypercall.h
> index 49eb5f1..1cd8046 100644
> --- a/xen/include/asm-x86/hypercall.h
> +++ b/xen/include/asm-x86/hypercall.h
> @@ -30,8 +30,8 @@ extern const hypercall_table_t pv_hypercall_table[];
>  void pv_hypercall(struct cpu_user_regs *regs);
>  #endif
> 
> -void hypercall_page_initialise_ring3_kernel(void *hypercall_page);
> -void hypercall_page_initialise_ring1_kernel(void *hypercall_page);
> +void pv_ring1_init_hypercall_page(void *ptr);
> +void pv_ring3_init_hypercall_page(void *ptr);
> 
>  /*
>   * Both do_mmuext_op() and do_mmu_update():
> --
> 2.1.4
> 

-- 
Brian Woods

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