Re: [Xen-devel] [PATCH 2/2] x86/HVM: use available linear->phys translations in REP MOVS/STOS handling

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: 08 June 2016 14:10
> To: xen-devel
> Cc: Paul Durrant
> Subject: [PATCH 2/2] x86/HVM: use available linear->phys translations in REP
> MOVS/STOS handling
> 
> If we have the translation result available already, we should also use
> is here. In my tests with Linux guests this eliminates all calls to
> hvmemul_linear_to_phys() out of the two functions being changed.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>

Reviewed-by: Paul Durrant <paul.durrant@xxxxxxxxxx>

> 
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -1156,6 +1156,7 @@ static int hvmemul_rep_movs(
>  {
>      struct hvm_emulate_ctxt *hvmemul_ctxt =
>          container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> +    struct hvm_vcpu_io *vio = &current->arch.hvm_vcpu.hvm_io;
>      unsigned long saddr, daddr, bytes;
>      paddr_t sgpa, dgpa;
>      uint32_t pfec = PFEC_page_present;
> @@ -1178,16 +1179,43 @@ static int hvmemul_rep_movs(
>      if ( hvmemul_ctxt->seg_reg[x86_seg_ss].attr.fields.dpl == 3 )
>          pfec |= PFEC_user_mode;
> 
> -    rc = hvmemul_linear_to_phys(
> -        saddr, &sgpa, bytes_per_rep, reps, pfec, hvmemul_ctxt);
> -    if ( rc != X86EMUL_OKAY )
> -        return rc;
> +    bytes = PAGE_SIZE - (saddr & ~PAGE_MASK);
> +    if ( vio->mmio_access.read_access &&
> +         (vio->mmio_gva == (saddr & PAGE_MASK)) &&
> +         bytes >= bytes_per_rep )
> +    {
> +        sgpa = pfn_to_paddr(vio->mmio_gpfn) | (saddr & ~PAGE_MASK);
> +        if ( *reps * bytes_per_rep > bytes )
> +            *reps = bytes / bytes_per_rep;
> +    }
> +    else
> +    {
> +        rc = hvmemul_linear_to_phys(saddr, &sgpa, bytes_per_rep, reps, pfec,
> +                                    hvmemul_ctxt);
> +        if ( rc != X86EMUL_OKAY )
> +            return rc;
> 
> -    rc = hvmemul_linear_to_phys(
> -        daddr, &dgpa, bytes_per_rep, reps,
> -        pfec | PFEC_write_access, hvmemul_ctxt);
> -    if ( rc != X86EMUL_OKAY )
> -        return rc;
> +        latch_linear_to_phys(vio, saddr, sgpa, 0);
> +    }
> +
> +    bytes = PAGE_SIZE - (daddr & ~PAGE_MASK);
> +    if ( vio->mmio_access.write_access &&
> +         (vio->mmio_gva == (daddr & PAGE_MASK)) &&
> +         bytes >= bytes_per_rep )
> +    {
> +        dgpa = pfn_to_paddr(vio->mmio_gpfn) | (daddr & ~PAGE_MASK);
> +        if ( *reps * bytes_per_rep > bytes )
> +            *reps = bytes / bytes_per_rep;
> +    }
> +    else
> +    {
> +        rc = hvmemul_linear_to_phys(daddr, &dgpa, bytes_per_rep, reps,
> +                                    pfec | PFEC_write_access, hvmemul_ctxt);
> +        if ( rc != X86EMUL_OKAY )
> +            return rc;
> +
> +        latch_linear_to_phys(vio, daddr, dgpa, 1);
> +    }
> 
>      /* Check for MMIO ops */
>      (void) get_gfn_query_unlocked(current->domain, sgpa >> PAGE_SHIFT,
> &sp2mt);
> @@ -1279,25 +1307,40 @@ static int hvmemul_rep_stos(
>  {
>      struct hvm_emulate_ctxt *hvmemul_ctxt =
>          container_of(ctxt, struct hvm_emulate_ctxt, ctxt);
> -    unsigned long addr;
> +    struct hvm_vcpu_io *vio = &current->arch.hvm_vcpu.hvm_io;
> +    unsigned long addr, bytes;
>      paddr_t gpa;
>      p2m_type_t p2mt;
>      bool_t df = !!(ctxt->regs->eflags & X86_EFLAGS_DF);
>      int rc = hvmemul_virtual_to_linear(seg, offset, bytes_per_rep, reps,
>                                         hvm_access_write, hvmemul_ctxt, 
> &addr);
> 
> -    if ( rc == X86EMUL_OKAY )
> +    if ( rc != X86EMUL_OKAY )
> +        return rc;
> +
> +    bytes = PAGE_SIZE - (addr & ~PAGE_MASK);
> +    if ( vio->mmio_access.write_access &&
> +         (vio->mmio_gva == (addr & PAGE_MASK)) &&
> +         bytes >= bytes_per_rep )
> +    {
> +        gpa = pfn_to_paddr(vio->mmio_gpfn) | (addr & ~PAGE_MASK);
> +        if ( *reps * bytes_per_rep > bytes )
> +            *reps = bytes / bytes_per_rep;
> +    }
> +    else
>      {
>          uint32_t pfec = PFEC_page_present | PFEC_write_access;
> 
>          if ( hvmemul_ctxt->seg_reg[x86_seg_ss].attr.fields.dpl == 3 )
>              pfec |= PFEC_user_mode;
> 
> -        rc = hvmemul_linear_to_phys(
> -            addr, &gpa, bytes_per_rep, reps, pfec, hvmemul_ctxt);
> +        rc = hvmemul_linear_to_phys(addr, &gpa, bytes_per_rep, reps, pfec,
> +                                    hvmemul_ctxt);
> +        if ( rc != X86EMUL_OKAY )
> +            return rc;
> +
> +        latch_linear_to_phys(vio, addr, gpa, 1);
>      }
> -    if ( rc != X86EMUL_OKAY )
> -        return rc;
> 
>      /* Check for MMIO op */
>      (void)get_gfn_query_unlocked(current->domain, gpa >> PAGE_SHIFT,
> &p2mt);
> 


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