Re: [PATCH v3 05/33] linux-user/hppa: Simplify init_guest_commpage

[Ilya Leoshkevich]

On Tue, Jan 02, 2024 at 12:57:40PM +1100, Richard Henderson wrote:
> If reserved_va, then we have already reserved the entire
> guest virtual address space; no need to remap page.
> If !reserved_va, then use MAP_FIXED_NOREPLACE.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  linux-user/elfload.c | 23 ++++++++++++++---------
>  1 file changed, 14 insertions(+), 9 deletions(-)
> 
> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
> index c166faabab..96d8d4f84c 100644
> --- a/linux-user/elfload.c
> +++ b/linux-user/elfload.c
> @@ -1969,16 +1969,21 @@ static inline void init_thread(struct target_pt_regs 
> *regs,
>  
>  static bool init_guest_commpage(void)
>  {
> -    void *want = g2h_untagged(LO_COMMPAGE);
> -    void *addr = mmap(want, qemu_host_page_size, PROT_NONE,
> -                      MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED, -1, 0);
> +    /* If reserved_va, then we have already mapped 0 page on the host. */
> +    if (!reserved_va) {
> +        int host_page_size = qemu_real_host_page_size();
> +        void *want, *addr;
>  
> -    if (addr == MAP_FAILED) {
> -        perror("Allocating guest commpage");
> -        exit(EXIT_FAILURE);
> -    }
> -    if (addr != want) {
> -        return false;
> +        want = g2h_untagged(LO_COMMPAGE);
> +        addr = mmap(want, host_page_size, PROT_NONE,
> +                    MAP_ANONYMOUS | MAP_PRIVATE | MAP_FIXED_NOREPLACE, -1, 
> 0);
> +        if (addr == MAP_FAILED) {
> +            perror("Allocating guest commpage");
> +            exit(EXIT_FAILURE);
> +        }
> +        if (addr != want) {
> +            return false;
> +        }
>      }
>  
>      /*
> -- 
> 2.34.1

Reviewed-by: Ilya Leoshkevich <iii@linux.ibm.com>