Re: [PATCH v4 25/27] target/i386/mshv: Use preallocated page for hvcall

["Daniel P. Berrangé" <berrange@redhat.com>]

On Tue, Sep 16, 2025 at 06:48:45PM +0200, Magnus Kulke wrote:
> There are hvcalls that are invoked during MMIO exits, the payload is of
> dynamic size. To avoid heap allocations we can use preallocated pages as
> in/out buffer for those calls. A page is reserved per vCPU and used for
> set/get register hv calls.
> 
> Signed-off-by: Magnus Kulke <magnuskulke@linux.microsoft.com>
> ---
>  accel/mshv/mshv-all.c       |  2 +-
>  include/system/mshv.h       |  7 +++++++
>  target/i386/mshv/mshv-cpu.c | 39 +++++++++++++++++++++++++------------
>  3 files changed, 35 insertions(+), 13 deletions(-)
> 
> diff --git a/accel/mshv/mshv-all.c b/accel/mshv/mshv-all.c
> index 2f7b325985..35a10f7a78 100644
> --- a/accel/mshv/mshv-all.c
> +++ b/accel/mshv/mshv-all.c
> @@ -398,8 +398,8 @@ static int mshv_init_vcpu(CPUState *cpu)
>      uint8_t vp_index = cpu->cpu_index;
>      int ret;
>  
> -    mshv_arch_init_vcpu(cpu);
>      cpu->accel = g_new0(AccelCPUState, 1);
> +    mshv_arch_init_vcpu(cpu);

This change can either be dropped, or squashed into the
earlier patch in this series that introduced this method.

>  
>      ret = mshv_create_vcpu(vm_fd, vp_index, &cpu->accel->cpufd);
>      if (ret < 0) {

> diff --git a/target/i386/mshv/mshv-cpu.c b/target/i386/mshv/mshv-cpu.c
> index 6b7e795a36..52afc6b303 100644
> --- a/target/i386/mshv/mshv-cpu.c
> +++ b/target/i386/mshv/mshv-cpu.c
> @@ -33,6 +33,11 @@
>  
>  #include <sys/ioctl.h>
>  
> +#define MAX_SIZE(a, b) ((a) > (b) ? (a) : (b))

Isn't this the same as the existing 'MAX(a, b)' macro in osdep.h ?

> +#define MAX_REGISTER_COUNT (MAX_SIZE(ARRAY_SIZE(STANDARD_REGISTER_NAMES), \
> +                            MAX_SIZE(ARRAY_SIZE(SPECIAL_REGISTER_NAMES), \
> +                                     ARRAY_SIZE(FPU_REGISTER_NAMES))))
> +




With regards,
Daniel
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