On Fri, Aug 23, 2019 at 10:13:14AM +0200, Thomas Hellström (VMware) wrote:
> +/*
> + * The high bandwidth out call. The low word of edx is presumed to have the
> + * HB and OUT bits set.
> + */
> +#define VMWARE_HYPERCALL_HB_OUT \
> + ALTERNATIVE_2("movw $" VMWARE_HYPERVISOR_PORT_HB ", %%dx; rep outsb", \
Hmm, that looks fishy:
This call in vmw_port_hb_out(), for example, gets converted to the asm
below (I've left in the asm touching only rDX).
# drivers/gpu/drm/vmwgfx/vmwgfx_msg.c:160: VMW_PORT_HB_OUT(
#NO_APP
movzwl 0(%rbp), %edx # channel_20(D)->channel_id, channel_20(D)->channel_id
...
sall $16, %edx #, tmp172
orl $3, %edx #, tmp173
this is adding channel_id and flags:
VMWARE_HYPERVISOR_HB | (channel->channel_id << 16) |
VMWARE_HYPERVISOR_OUT,
the $3 being (VMWARE_HYPERVISOR_HB | VMWARE_HYPERVISOR_OUT).
movslq %edx, %rdx # tmp173, tmp174
Here it is sign-extending it.
#APP
# 160 "drivers/gpu/drm/vmwgfx/vmwgfx_msg.c" 1
push %rbp;mov %r8, %rbp;# ALT: oldinstr2 # bp
661:
movw $0x5659, %dx; rep outsb
And now here you're overwriting the low word of %edx. And now it
contains:
0x[channel_id]5659
and the low word doesn't contain the 3, i.e., (VMWARE_HYPERVISOR_HB |
VMWARE_HYPERVISOR_OUT) anymore. And that's before you do the hypercall
so I'm guessing that cannot be right.
Or?
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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