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xen-devel
Re: [Xen-devel] Question on shadow_invlpg return value handling.
At 10:21 +0530 on 27 Mar (1174990916), aditya shevalkar wrote:
> Can anyone explain me where does this return values from sh_invlpg are used.
> The comment is given below:
> /* Called when the guest requests an invlpg. Returns 1 if the invlpg
> * instruction should be issued on the hardware, or 0 if it's safe not
> * to do so. */
> I have followed the following path of function call in my study of the
> function.
> vmx_vmexit_do_invlpg(va) à shadow_invlpg(v, va) à sh_invlpg(struct vcpu *v,
> unsigned long va).
The VMX (and SVM) code ignores the return code of shadow_invlpg at the
moment, because they both flush the entire TLB on every VM entry anyway
(AMD's hardware support for tagged TLBs is apparently not quite useable
yet).
arch/x86/mm.c, which handles PV guests, uses the return code correctly,
e.g.:
case MMUEXT_INVLPG_LOCAL:
if ( !shadow_mode_enabled(d)
|| shadow_invlpg(v, op.arg1.linear_addr) != 0 )
local_flush_tlb_one(op.arg1.linear_addr);
break;
Cheers,
Tim.
--
Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>, XenSource UK Limited
Registered office c/o EC2Y 5EB, UK; company number 05334508
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